Patent Publication Number: US-11047919-B2

Title: Open wire detection system and method therefor

Description:
BACKGROUND 
     Field 
     This disclosure relates generally to circuits, and more specifically, to an open wire detection system. 
     Related Art 
     Today, a broad range of products from cell phones to electric vehicles, for example, are powered by rechargeable batteries. Semiconductor devices including battery management circuits are generally connected to terminals of the rechargeable batteries to control charging and monitor the state of charge, health, and other parameters of the batteries. In safety critical applications, loss of a connection to a terminal of a battery can have dire affects. Therefore, a need exists for improved safety in the case of an open circuit condition. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example and is not limited by the accompanying figures, in which like references indicate similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. 
         FIG. 1  illustrates, in simplified block diagram form, an example battery management system in accordance with an embodiment. 
         FIG. 2  illustrates, in schematic diagram form, a first example of a more detailed battery management system in accordance with an embodiment. 
         FIG. 3  illustrates, in schematic diagram form, a second example of a more detailed battery management system in accordance with an embodiment. 
         FIG. 4  illustrates, in flow diagram form, an example method of detecting an open wire in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Generally, there is provided, a battery management system that includes open wire detection. A diode circuit is coupled between terminals of a battery management unit. The terminals of the battery management unit are connected to terminals of a battery cell by way of conductive paths. Monitor circuitry of the battery management unit is configured to monitor a voltage across the diode circuit. An open circuit in a conductive path is detected when a voltage across the diode circuit exceeds a predetermined threshold. 
       FIG. 1  illustrates, in simplified block diagram form, an example battery management system  100  in accordance with an embodiment. System  100  includes a battery cell  102  and a battery management unit  104 . Battery cell  102  may be any suitable rechargeable battery cell (e.g., lithium ion, sealed lead acid). Battery management unit  104  is formed as an integrated circuit and serves to manage and monitor the state of charge, health, and operating conditions of the battery cell  102 . The battery management unit  104  includes storage circuitry (e.g., registers, memory) for storing parameters (e.g., battery health, conditions) and communication circuitry for communicating stored parameters with other battery management units and/or a main battery management controller by way of output labeled OUT. 
     In this embodiment, battery management unit  104  includes circuitry for open wire detection which is a safety critical feature when employed in vehicles (e.g., automobiles, trucks). The battery management unit  104  includes terminals for connections to battery cell  102 . Conductive paths  106 - 112  provide electrical connections between the positive (+) and negative (−) terminals of battery cell  102  and respective terminals (HB, HS, LB, LS) of the battery management unit  104 . The conductive paths  106 - 112  include wiring, conductive traces on a printed circuit board, solder connections, and the like, which forms the electrical connections between the battery cell  102  and the battery management unit  104 . In this embodiment, a first conductive path  106  is coupled between the positive terminal of battery cell  104  and the high-side battery terminal labeled HB. Likewise, a second conductive path  108  is coupled between the positive terminal of battery cell  102  and the high-side sense terminal labeled HS. A third conductive path  110  is coupled between the negative terminal of battery cell  102  and the low-side battery terminal labeled LB, and a fourth conductive path  112  is coupled between the negative terminal of battery cell  102  and the low-side sense terminal labeled LS. 
     In the event that an open circuit occurs in any of conductive paths  106 - 112 , an open wire error indication is stored and communicated with the main battery management controller by way of the output OUT. The term “open wire” as used herein, refers to an open circuit in a conductive path (e.g., conductive paths  106 - 112 ). The electrical connections formed by conductive paths  106  and  110  are used to provide an operating voltage (e.g., by way of the battery cell  102 ) to circuitry of the battery management unit  104 . The electrical connections formed by conductive paths  108  and  112  are used by the battery management unit  104  to sense or monitor voltage levels of the battery cell  102 . 
       FIG. 2  illustrates, in schematic diagram form, a first more detailed example battery management system  200  in accordance with an embodiment. System  200  includes battery cell  102  and battery management unit  104  shown in more detail. As described above, the battery cell  102  may be any suitable rechargeable battery cell type. In this embodiment, battery management unit  104  is formed as an integrated circuit and includes circuitry for open wire detection. 
     In this embodiment, the battery management unit  104  includes terminals  202 - 208  labeled HB, HS, LB, and LS respectively for electrical connections to battery cell  102 , diode circuits  226  and  228 , a first analog to digital converter (ADC)  210 , a second ADC  212 , logic block  214 , and voltage regulator  224 . Terminals HB, HS, LB, and LS may be in the form of bonding pads or package terminals of the battery management unit  104 , for example. Conductive paths  106 - 112  provide electrical connections between the positive (+) and negative (−) terminals of battery cell  102  and respective terminals HB, HS, LB, and LS of the battery management unit  104 . The conductive paths  106 - 112  include wiring, conductive traces on a printed circuit board, solder connections, and the like, which forms the electrical connections between the battery cell  102  and the battery management unit  104 . In this embodiment, a first conductive path  106  is coupled between the positive terminal of battery cell  104  and the high-side battery terminal labeled HB, and a second conductive path  108  is coupled between the positive terminal of battery cell  104  and the high-side sense terminal labeled HS. Likewise, a third conductive path  110  is coupled between the negative terminal of battery cell  104  and the low-side battery terminal labeled LB, and a fourth conductive path  112  is coupled between the negative terminal of battery cell  104  and the low-side sense terminal labeled LS. 
     First diode circuit  226  is coupled between the HS and HB terminals and second diode circuit  228  is coupled between the LS and LB terminals of the battery management unit  104 . The first diode circuit  226  includes a first diode  216  and a second diode  218  arranged in an antiparallel configuration. The term “antiparallel” as used herein, refers to a pair of diodes connected in parallel with reverse polarities. In this arrangement, diode  216  has an anode terminal connected to the HS terminal and a cathode terminal connected to the HB terminal, and diode  218  has a cathode terminal connected to the HS terminal and an anode terminal connected to the HB terminal. The second diode circuit  228  includes a first diode  220  and a second diode  222  arranged in an antiparallel configuration. In this arrangement, diode  220  has an anode terminal connected to the LS terminal and a cathode terminal connected to the LB terminal, and diode  222  has a cathode terminal connected to the LS terminal and an anode terminal connected to the LB terminal. 
     First ADC  210  labeled ADC is configured to monitor and measure voltages at the HS and LS terminals respectively. ADC  210  includes a first input coupled to the HS terminal, a second input coupled to the LS terminal, and an output labeled ADCOUT coupled to the logic block  214  for providing digital conversion values representative of measured voltages at the HS and LS terminals. Second ADC  212  labeled ADC 2  is configured to monitor and measure voltages at the HB and LB terminals respectively. ADC  212  includes a first input coupled to the HB terminal, a second input coupled to the LB terminal, and an output labeled ADC 2 OUT coupled to the logic block  214  for providing digital conversion values representative of measured voltages at the HB and LB terminals. In an embodiment, ADC  210  is characterized as a high-resolution ADC (e.g., 12-bit ADC) and ADC  212  is characterized as a low-resolution ADC (e.g., 8-bit ADC). In other embodiments, both ADCs  210  and  212  may be characterized as high-resolution ADCs. 
     ADC  210  and ADC  212  along with logic block  214  serve as a detect circuit configured to determine that an open wire exists on conductive paths  106 - 112  when monitored voltages across the diode circuits  226  and  228  exceed predetermined thresholds, store an open wire error indication, and communicate such error indication with the main battery management controller by way of the output OUT. The diode circuits  226  and  228  serve as detection diode circuits configured for detecting the open wire by having a detectable voltage across the detection diode circuits when the open wire exists. In an embodiment, the first and second diode circuits  226  and  228  are formed as electrostatic discharge (ESD) diode circuits and are utilized as the detection diode circuits. In this arrangement, the first and second diode circuits  226  and  228  are configured to protect circuitry of the battery management unit  104  during ESD events at the HS, HB, LS, and LB terminals in addition to serving as detection diode circuits. In an embodiment, communications circuitry of logic block  214  for communicating with the main battery management controller may be a serial communication interface. In other embodiments, other communication circuitry for communicating with the main battery management controller may be employed. 
     Logic block  214  includes logic circuits configured to perform control, computational, operational, and communication functions among other functions. The logic block  214  is coupled to receive conversion values from ADCs  210  and  212  that are representative of voltages measured at HB, HS, LB, and LS terminals respectively. From these conversion values, voltages across the diode circuits  226  and  228  are determined. In a first example, when conductive paths  106  and  108  are intact, the voltage measured at the HS terminal is approximately the same as the voltage measured at the HB terminal. In turn, circuitry in the logic block  214  performs a subtraction operation using the measured voltage values as operands and provides a result. In this example, the result is approximately 0 (zero) volts measured across diode circuit  226 . 
     In a second example, when an open circuit occurs in conductive path  106 , the voltage measured at the HB terminal is significantly lower than the voltage measured at the HS terminal. Because the HB terminal is no longer connected to the battery terminal, a voltage drop occurs across the diode circuit  226 . Performing a subtraction operation (e.g., HS terminal voltage minus HB terminal voltage) in the logic block  214  using the measured voltage values as operands provides a result of as much as approximately a diode threshold voltage measured across diode circuit  226 . In this example, the measured voltage across diode circuit  226  may be in a range of 100 to 700 millivolts. A first predetermined error threshold value may be set at +50 millivolts, for example, in a control register of logic block  214 . The measured voltage is compared with the error threshold value and when exceeded, the logic block  214  generates an HB open wire error indication. Because the measured voltage across diode circuit  226  exceeds the first predetermined error threshold, the HB open wire error indication may be stored as a flag in an error register of logic block  214  and communicated with a main battery management controller by way of communications circuitry of logic block  214  at output OUT. 
     In a third example, when an open circuit occurs in conductive path  108 , the voltage measured at the HS terminal is significantly lower than the voltage measured at the HB terminal. Because the HS terminal is no longer connected to the battery terminal, a voltage drop occurs across the diode circuit  226 . Performing a subtraction operation (e.g., HS terminal voltage minus HB terminal voltage) in the logic block  214  using the measured voltage values as operands provides a result of as much as approximately a diode threshold voltage measured across diode circuit  226 . In this example, the measured voltage across diode circuit  226  may be in a range of −100 to −700 millivolts. A second predetermined error threshold value may be set at −50 millivolts, for example, in a control register of logic block  214 . In this example, the second threshold has a same magnitude as the first threshold described in the second example above. The measured voltage is compared with the error threshold value and when exceeded, the logic block  214  generates an HS open wire error indication. Because the measured voltage across diode circuit  226  exceeds the second predetermined error threshold, the HS open wire error indication may be stored as a flag in an error register of logic block  214  and communicated with a main battery management controller by way of communications circuitry of logic block  214  at output OUT. 
     In a fourth example, when an open circuit occurs in conductive path  110 , the voltage measured at the LB terminal is significantly higher than the voltage measured at the LS terminal. Because the LB terminal is no longer connected to the battery terminal, a voltage increase occurs across the diode circuit  228 . Performing a subtraction operation (e.g., LS terminal voltage minus LB terminal voltage) in the logic block  214  using the measured voltage values as operands provides a result of as much as approximately a diode threshold voltage measured across diode circuit  228 . In this example, the measured voltage across diode circuit  228  may be in a range of −100 to −700 millivolts. A third predetermined error threshold value may be set at −50 millivolts, for example, in a control register of logic block  214 . The measured voltage across diode circuit  228  is compared with the third error predetermined threshold value and when exceeded, the logic block  214  generates an LB open wire error indication. Because the measured voltage across diode circuit  226  exceeds the third predetermined error threshold, the LB open wire error indication may be stored as a flag in an error register of logic block  214  and communicated with a main battery management controller by way of communications circuitry of logic block  214  at output OUT. 
     In a fifth example, when an open circuit occurs in conductive path  112 , the voltage measured at the LS terminal is significantly higher than the voltage measured at the LB terminal. Because the LS terminal is no longer connected to the battery terminal, a voltage increase occurs across the diode circuit  228 . Performing a subtraction operation (e.g., LS terminal voltage minus LB terminal voltage) in the logic block  214  using the measured voltage values as operands provides a result of as much as approximately a diode threshold voltage measured across diode circuit  228 . In this example, the measured voltage across diode circuit  228  may be in a range of 100 to 700 millivolts. A fourth predetermined error threshold value may be set at +50 millivolts, for example, in a control register of logic block  214 . In this example, the fourth threshold has a same magnitude as the third threshold described in the fourth example above. The measured voltage across diode circuit  228  is compared with the third error predetermined threshold value and when exceeded, the logic block  214  generates an LS open wire error indication. Because the measured voltage across diode circuit  226  exceeds the fourth predetermined error threshold, the LS open wire error indication may be stored as a flag in an error register of logic block  214  and communicated with a main battery management controller by way of communications circuitry of logic block  214  at output OUT. 
     Voltage regulator  224  is configured to provide an operating voltage VSUPPLY to circuitry of ADC  210 , ADC  212 , and logic block  214 . Voltage regulator  224  includes a first input coupled to the positive terminal of battery cell  102  by way of the HB terminal and conductive path  106  and a second input coupled to the negative terminal of battery cell  102  by way of the LB terminal and conductive path  110 . Voltage regulator  224  includes an output coupled to provide operating voltage VSUPPLY. In this embodiment, voltage regulator  224  is characterized as a low-dropout (LDO) voltage regulator. In other embodiments, other types of voltage regulators may be employed as voltage regulator  224 . 
       FIG. 3  illustrates, in schematic diagram form, a second more detailed example battery management system  300  in accordance with an embodiment. System  300  includes battery cell  102  and battery management unit  104  shown in more detail. As described above, the battery cell  102  may be any suitable rechargeable battery cell type. In this embodiment, battery management unit  104  is formed as an integrated circuit and includes circuitry for open wire detection. 
     In this embodiment, the battery management unit  104  includes terminals  302 - 308  labeled HB, HS, LB, and LS respectively for electrical connections to battery cell  102 , diode circuits  334  and  336 , an ADC  310 , a first comparator circuit  338 , a second comparator circuit  340 , logic block  314 , and voltage regulator  324 . Conductive paths  106 - 112  provide electrical connections between the positive (+) and negative (−) terminals of battery cell  102  and respective terminals HB, HS, LB, and LS of the battery management unit  104 . The conductive paths  106 - 112  include wiring, conductive traces on a printed circuit board, solder connections, and the like, which forms the electrical connections between the battery cell  102  and the battery management unit  104 . In this embodiment, a first conductive path  106  is coupled between the positive terminal of battery cell  104  and the high-side battery terminal labeled HB, and a second conductive path  108  is coupled between the positive terminal of battery cell  104  and the high-side sense terminal labeled HS. Likewise, a third conductive path  110  is coupled between the negative terminal of battery cell  104  and the low-side battery terminal labeled LB, and a fourth conductive path  112  is coupled between the negative terminal of battery cell  104  and the low-side sense terminal labeled LS. 
     First diode circuit  334  is coupled between the HS and HB terminals and second diode circuit  336  is coupled between the LS and LB terminals of the battery management unit  104 . The first diode circuit  334  includes a first diode  316  and a second diode  318  arranged in an antiparallel configuration. In this arrangement, diode  316  has an anode terminal connected to the HS terminal and a cathode terminal connected to the HB terminal, and diode  318  has a cathode terminal connected to the HS terminal and an anode terminal connected to the HB terminal. The second diode circuit  336  includes a first diode  320  and a second diode  322  arranged in an antiparallel configuration. In this arrangement, diode  320  has an anode terminal connected to the LS terminal and a cathode terminal connected to the LB terminal, and diode  322  has a cathode terminal connected to the LS terminal and an anode terminal connected to the LB terminal. 
     ADC  310  labeled ADC is configured to monitor and measure voltages at the HS and LS terminals respectively. ADC  310  includes a first input coupled to the HS terminal, a second input coupled to the LS terminal, and an output labeled ADCOUT coupled to the logic block  314  for providing digital conversion values representative of measured voltages at the HS and LS terminals. In an embodiment, ADC  310  is characterized as a high-resolution ADC (e.g., 12-bit ADC). 
     Comparator circuits  338  and  340  are configured to monitor voltages across respective diode circuits  334  and  336 . First comparator circuit  338  includes a first comparator  326  and a second comparator  328  connected in parallel across diode circuit  334  and arranged with opposite input polarities. Comparator  326  includes a non-inverting (+) input connected to the HS terminal, an inverting input (−) connected to the HB terminal, and an output for providing a compare signal labeled HBCMP to logic block  314 . Comparator  328  includes a non-inverting (+) input connected to the HB terminal, an inverting input (−) connected to the HS terminal, and an output for providing a compare signal labeled HSCMP to logic block  314 . 
     In an embodiment, comparators  326  and  328  are each configured to include a predetermined threshold voltage (e.g., 50 millivolts). For example, when a monitored voltage at the non-inverting input exceeds a voltage at the inverting input by the predetermined threshold voltage amount, the output signal (e.g., HSCMP, HBCMP) is at a logic high level. When the monitored voltage at the non-inverting input is less than the predetermined threshold voltage relative to the voltage at the inverting input, the output signal (e.g., HSCMP, HBCMP) is at a logic low level. Because comparators  326  and  328  are arranged with opposite input polarities, only one of the HSCMP and HBCMP output signals can be at a logic high level at any given time. 
     Similarly, second comparator circuit  340  includes a first comparator  330  and a second comparator  332  connected in parallel across diode circuit  336  and arranged with opposite input polarities. Comparator  330  includes a non-inverting (+) input connected to the LB terminal, an inverting input (−) connected to the LS terminal, and an output for providing a compare signal labeled LBCMP to logic block  314 . Comparator  332  includes a non-inverting (+) input connected to the LS terminal, an inverting input (−) connected to the LB terminal, and an output for providing a compare signal labeled LSCMP to logic block  314 . 
     In an embodiment, comparators  330  and  332  are each configured to include a predetermined threshold voltage (e.g., 50 millivolts). For example, when a monitored voltage at the non-inverting input exceeds a voltage at the inverting input by the predetermined threshold voltage amount, the output signal (e.g., LSCMP, LBCMP) is at a logic high level. When the monitored voltage at the non-inverting input is less than the predetermined threshold voltage relative to the voltage at the inverting input, the output signal (e.g., LSCMP, LBCMP) is at a logic low level. Because comparators  330  and  332  are arranged with opposite input polarities, only one of the LSCMP and LBCMP output signals can be at a logic high level at any given time. 
     Comparator circuits  338  and  340  along with logic block  314  serve as a detect circuit configured to determine that an open wire exists on conductive paths  106 - 112  when voltages across the diode circuits  334  and  336  exceed predetermined thresholds, store an open wire error indication, and communicate such error indication with the main battery management controller by way of the output OUT. The diode circuits  334  and  336  serve as detection diode circuits configured for detecting the open wire by having a detectable voltage across the detection diode circuits when the open wire exists. In an embodiment, the first and second diode circuits  334  and  336  are formed as electrostatic discharge (ESD) diode circuits and are utilized as the detection diode circuits. In this arrangement, the first and second diode circuits  334  and  336  are configured to protect circuitry of the battery management unit  104  during ESD events at the HS, HB, LS, and LB terminals in addition to serving as detection diode circuits. In an embodiment, communications circuitry of logic block  314  for communicating with the main battery management controller may be a serial communication interface. In other embodiments, other communication circuitry for communicating with the main battery management controller may be employed. 
     Logic block  314  includes logic circuits configured to perform control, operational, and communication functions among other functions. The logic block  314  is coupled to receive output signals HBCMP, HSCMP, LBCMP, and LSCMP from comparator circuits  338  and  340 . Each of output signals HBCMP, HSCMP, LBCMP, and LSCMP provides an indication when a voltage across respective diode circuits  334  and  336  exceeds a predetermined threshold. 
     In a first example, when conductive paths  106  and  108  are intact, the voltage at the HS terminal is approximately the same as the voltage at the HB terminal. Accordingly, approximately 0 (zero) volts exists across diode circuit  334  and output signals HBCMP and HSCMP are at a logic low level. Likewise, when conductive paths  110  and  112  are intact, the voltage at the LS terminal is approximately the same as the voltage at the LB terminal. Accordingly, approximately 0 (zero) volts exists across diode circuit  336  and output signals LBCMP and LSCMP are at a logic low level. 
     In a second example, when an open circuit occurs in conductive path  106 , the voltage at the HB terminal is significantly lower than the voltage at the HS terminal. Because the HB terminal is no longer connected to the battery terminal, a voltage drop occurs across the diode circuit  334 . A resulting voltage across diode circuit  334  may be in a range of 100 to 700 millivolts. In this example, the comparator  326  is configured to have a first predetermined error threshold value set at +50 millivolts relative to the voltage at the HB terminal. Because the voltage across diode circuit  334  exceeds the first predetermined error threshold, the output signal HBCMP from comparator  326  is at a logic high level and provides an HB open wire error indication. The HB open wire error indication may be stored as a flag in an error register of logic block  314  and communicated with a main battery management controller by way of communications circuitry of logic block  314  at output OUT. 
     In a third example, when an open circuit occurs in conductive path  108 , the voltage at the HS terminal is significantly lower than the voltage at the HB terminal. Because the HS terminal is no longer connected to the battery terminal, a voltage drop occurs across the diode circuit  334 . A resulting voltage across diode circuit  334  may be in a range of −100 to −700 millivolts. In this example, the comparator  328  is configured to have a second predetermined error threshold value set at −50 millivolts relative to the voltage at the HB terminal. Because the voltage across diode circuit  334  exceeds the second predetermined error threshold, the output signal HSCMP from comparator  328  is at a logic high level and provides an HS open wire error indication. The HS open wire error indication may be stored as a flag in an error register of logic block  314  and communicated with a main battery management controller by way of communications circuitry of logic block  314  at output OUT. 
     In a fourth example, when an open circuit occurs in conductive path  110 , the voltage at the LB terminal is significantly higher than the voltage at the LS terminal. Because the LB terminal is no longer connected to the battery terminal, a voltage increase occurs across the diode circuit  336 . A resulting voltage across diode circuit  336  may be in a range of −100 to −700 millivolts. In this example, the comparator  330  is configured to have a third predetermined error threshold value set at −50 millivolts relative to the voltage at the LB terminal. Because the voltage across diode circuit  336  exceeds the third predetermined error threshold, the output signal LBCMP from comparator  330  is at a logic high level and provides an LB open wire error indication. The LB open wire error indication may be stored as a flag in an error register of logic block  314  and communicated with a main battery management controller by way of communications circuitry of logic block  314  at output OUT. 
     In a fifth example, when an open circuit occurs in conductive path  112 , the voltage at the LS terminal is significantly higher than the voltage at the LB terminal. Because the LS terminal is no longer connected to the battery terminal, a voltage increase occurs across the diode circuit  336 . A resulting voltage across diode circuit  336  may be in a range of 100 to 700 millivolts. In this example, the comparator  332  is configured to have a fourth predetermined error threshold value set at +50 millivolts relative to the voltage at the LB terminal. Because the voltage across diode circuit  336  exceeds the fourth predetermined error threshold, the output signal LSCMP from comparator  332  is at a logic high level and provides an LS open wire error indication. The LS open wire error indication may be stored as a flag in an error register of logic block  314  and communicated with a main battery management controller by way of communications circuitry of logic block  314  at output OUT. 
     Voltage regulator  324  is configured to provide an operating voltage VSUPPLY to circuitry of ADC  310 , comparator circuits  334  and  336 , and logic block  314 . Voltage regulator  324  includes a first input coupled to the positive terminal of battery cell  102  by way of the HB terminal and conductive path  106  and a second input coupled to the negative terminal of battery cell  102  by way of the LB terminal and conductive path  110 . Voltage regulator  324  includes an output coupled to provide operating voltage VSUPPLY. In this embodiment, voltage regulator  324  is characterized as a low-dropout (LDO) voltage regulator. In other embodiments, other types of voltage regulators may be employed as voltage regulator  324 . 
       FIG. 4  illustrates, in simplified flow diagram form, an example method  400  of detecting an open wire in accordance with an embodiment. In this embodiment, the method  400  includes detecting an open wire (e.g., an open circuit in any of conductive paths  106 - 112 ) by monitoring voltages across diode circuits (e.g., diode circuits  226 - 228 ,  334 - 336 ). In the event that a monitored voltage across a diode circuit exceeds a predetermined threshold, an open wire is detected, and an open wire error indication is stored as an error flag. The diode circuits serve as detection diode circuits configured for detecting the open wire by having a detectable voltage across the detection diode circuits when the open wire exists. 
     At step  402 , monitor voltage across a first diode circuit. In this embodiment, the first diode circuit (e.g., diode circuit  226  of  FIG. 2 , diode circuit  334  of  FIG. 3 ) is formed as an antiparallel diode pair as described above. Circuitry such as the ADCs  210  and  212  in the example battery management unit  104  of  FIG. 2  and the comparator circuit  338  in the example battery management unit  104  of  FIG. 3  are coupled to monitor voltages across the first diode circuit. 
     At step  404 , determine whether the monitored voltage across the first diode circuit exceeds a first threshold. When an open circuit exist in a conductive path such as conductive paths  106 - 108  between the positive terminal of battery cell  102  and battery management unit  104 , a significant voltage (e.g., 100-700 millivolts) exists across the first diode circuit. Circuitry of the battery management unit as described above is configured to generate an error indication when the monitored voltage exceeds a predetermined threshold. If the monitored voltage exceeds the first threshold, then (yes) proceed at step  406 . If the monitored voltage does not exceed the first threshold, then (no) proceed at step  408 . 
     At step  406 , set a first error flag. When the monitored voltage exceeds the first threshold, an error indication is generated and stored by setting a first error flag in an error register, for example, such as located in logic block  214  of  FIG. 2  and logic block  314  of  FIG. 3 . 
     At step  408 , determine whether the monitored voltage across the first diode circuit exceeds a second threshold. In this embodiment, the second threshold by have a same magnitude as the first threshold but opposite polarity. If the monitored voltage exceeds the first threshold, then (yes) proceed at step  410 . If the monitored voltage does not exceed the first threshold, then (no) proceed at step  412 . 
     At step  410 , set a second error flag. When the monitored voltage exceeds the second threshold, an error indication is generated and stored by setting a second error flag in an error register, for example, such as located in logic block  214  of  FIG. 2  and logic block  314  of  FIG. 3 . 
     At step  412 , monitor voltage across a second diode circuit. In this embodiment, the second diode circuit (e.g., diode circuit  228  of  FIG. 2 , diode circuit  336  of  FIG. 3 ) is formed as an antiparallel diode pair as described above. Circuitry such as the ADCs  210  and  212  in the example battery management unit  104  of  FIG. 2  and the comparator circuit  340  in the example battery management unit  104  of  FIG. 3  are coupled to monitor voltages across the second diode circuit. 
     At step  414 , determine whether the monitored voltage across the second diode circuit exceeds a third threshold. When an open circuit exist in a conductive path such as conductive paths  110 - 112  between the negative terminal of battery cell  102  and battery management unit  104 , a significant voltage (e.g., 100-700 millivolts) exists across the second diode circuit. If the monitored voltage exceeds the third threshold, then (yes) proceed at step  416 . If the monitored voltage does not exceed the third threshold, then (no) proceed at step  418 . 
     At step  416 , set a third error flag. When the monitored voltage exceeds the third threshold, an error indication is generated and stored by setting a third error flag in an error register, for example, such as located in logic block  214  of  FIG. 2  and logic block  314  of  FIG. 3 . 
     At step  418 , determine whether the monitored voltage across the second diode circuit exceeds a fourth threshold. In this embodiment, the fourth threshold by have a same magnitude as the third threshold but opposite polarity. If the monitored voltage exceeds the fourth threshold, then (yes) proceed at step  420 . If the monitored voltage does not exceed the first threshold, then (no) proceed at step  402 . 
     At step  420 , set a fourth error flag. When the monitored voltage exceeds the fourth threshold, an error indication is generated and stored by setting a fourth error flag in an error register, for example, such as located in logic block  214  of  FIG. 2  and logic block  314  of  FIG. 3 . 
     Generally, there is provided, a semiconductor device including a first diode having an anode terminal coupled to a first terminal and a cathode terminal coupled to a second terminal, the first and second terminals configured for connection to a first battery cell terminal by way of a first conductive path and a second conductive path; and a detect circuit coupled to the first diode, the detect circuit configured to provide a first open wire indication when a first voltage across the first diode exceeds a first threshold. The device may further include a second diode coupled in parallel with the first diode, the second diode having a cathode terminal coupled to the first terminal and an anode terminal coupled to the second terminal; wherein the detect circuit is further configured to provide a second open wire indication when the first voltage exceeds a second threshold. The first voltage across the first diode may exceed the first threshold when an open circuit occurs in the second conductive path, and wherein the first voltage across the second diode may exceed the second threshold when an open circuit occurs in the first conductive path. The detect circuit may include a first comparator having a non-inverting input coupled to the anode terminal of the first diode and an inverting input coupled to the cathode terminal of the first diode, the first comparator configured to provide a first output signal indicative of the first voltage exceeding the first threshold; and a second comparator having a non-inverting input coupled to the anode terminal of the second diode and an inverting input coupled to the cathode terminal of the second diode, the second comparator configured to provide a second output signal indicative of the first voltage exceeding the second threshold. The device may further include a logic block configured to store a first value in a first register bit based on the first output signal and store the first value in a second register bit based on the second output signal, the logic block further configured to communicate values stored in the register bits by way of serial communication circuitry. The device may further include a third diode having an anode terminal coupled to a third terminal and a cathode terminal coupled to a fourth terminal, the third and fourth terminals configured for connection to a second battery cell terminal by way of a third conductive path and a fourth conductive path; wherein the detect circuit is further coupled to detect a second voltage across the third diode and is further configured to provide a third open wire indication when the second voltage exceeds a third threshold. The device may further include a fourth diode coupled in parallel with the third diode, the fourth diode having a cathode terminal coupled to the third terminal and an anode terminal coupled to the fourth terminal; wherein the detect circuit is further configured to provide a fourth open wire indication when the second voltage exceeds a fourth threshold. The detect circuit may further include a first analog to digital converter (ADC) having a first input coupled to the first terminal and a second input coupled to the third terminal, the first ADC having an output coupled to a logic block to provide a first conversion value corresponding to a first terminal voltage at the first input and a second conversion value corresponding to a third terminal voltage at the second input; and a second ADC having a first input coupled to the second terminal and a second input coupled to the fourth terminal, the second ADC having an output coupled to the logic block to provide a third conversion value corresponding to a second terminal voltage at the first input and a fourth conversion value corresponding to a fourth terminal voltage at the second input. The logic block may be configured to calculate the first voltage or the second voltage based on the first, second, third and fourth conversion values. 
     In another embodiment, there is provided, a semiconductor device including a first antiparallel diode pair coupled between a first terminal and a second terminal, the first and second terminals configured for connection to a positive battery cell terminal by way of a first conductive path and a second conductive path; and a detect circuit coupled to the first antiparallel diode pair, the detect circuit configured to provide a first open wire indication when a first voltage across the first antiparallel diode pair exceeds a first threshold. The detect circuit may be further configured to provide a second open wire indication when the first voltage exceeds a second threshold, the second threshold having a same magnitude as the first threshold. The first voltage across the first antiparallel diode pair may exceed the first threshold when an open circuit occurs in the first conductive path, and wherein the first voltage across the first antiparallel diode pair may exceed the second threshold when an open circuit occurs in the second conductive path. The detect circuit may include a first comparator having a non-inverting input coupled to the first terminal and an inverting input coupled to the second terminal, the first comparator configured to provide a first output signal indicative of the first voltage exceeding the first threshold; and a second comparator having a non-inverting input coupled to the second terminal of and an inverting input coupled to the first terminal, the second comparator configured to provide a second output signal indicative of the first voltage exceeding the second threshold. The device may further include a second antiparallel diode pair coupled between a third terminal and a fourth terminal, the third and fourth terminals configured for connection to a negative battery cell terminal by way of a third conductive path and a fourth conductive path; wherein the detect circuit is further coupled to detect a second voltage across the second antiparallel diode pair, the detect circuit further configured to provide a third open wire indication when the second voltage exceeds a third threshold. The device may further include a voltage regulator coupled between the second terminal and the fourth terminal, the voltage regulator configured to provide an operating voltage for the detect circuit. The detect circuit may include a first ADC having a first input coupled to the first terminal, a second input coupled to the third terminal, and an output coupled to a logic block, the first ADC configured to provide at the output a first conversion value corresponding to a first terminal voltage at the first input and a second conversion value corresponding to a third terminal voltage at the second input; and a second ADC having a first input coupled to the second terminal and a second input coupled to the fourth terminal, and an output coupled to the logic block, the second ADC configured to provide at the output a third conversion value corresponding to a second terminal voltage at the first input and a fourth conversion value corresponding to a fourth terminal voltage at the second input. The logic block may be configured to calculate the first voltage or the second voltage based on the first, second, third and fourth conversion values. 
     In yet another embodiment, there is provided, a method including providing a first diode circuit between a first terminal and a second terminal, the first and second terminals configured for connection to a first battery cell terminal by way of a first conductive path and a second conductive path; determining that a first voltage across the first diode circuit exceeds a first threshold; generating a first open wire indication when the first voltage across the first diode circuit exceeds a first threshold. The first voltage across the first diode circuit may exceed the first threshold when an open circuit occurs in the first conductive path or the second conductive path. The first diode circuit may be configured to protect circuitry when an ESD event occurs at the first or second terminals. 
     By now it should be appreciated that there has been provided, a battery management system that includes open wire detection. A diode circuit is coupled between terminals of a battery management unit. The terminals of the battery management unit are connected to terminals of a battery cell by way of conductive paths. Monitor circuitry of the battery management unit is configured to monitor a voltage across the diode circuit. An open circuit in a conductive path is detected when a voltage across the diode circuit exceeds a predetermined threshold. 
     Because the apparatus implementing the present invention is, for the most part, composed of electronic components and circuits known to those skilled in the art, circuit details will not be explained in any greater extent than that considered necessary as illustrated above, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention. 
     Although the invention has been described with respect to specific conductivity types or polarity of potentials, skilled artisans appreciated that conductivity types and polarities of potentials may be reversed. 
     Architectures depicted herein are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In an abstract, but still definite sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality. 
     Furthermore, those skilled in the art will recognize that boundaries between the functionality of the above described operations are merely illustrative. The functionality of multiple operations may be combined into a single operation, and/or the functionality of a single operation may be distributed in additional operations. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments. 
     Although the invention is described herein with reference to specific embodiments, various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention. Any benefits, advantages, or solutions to problems that are described herein with regard to specific embodiments are not intended to be construed as a critical, required, or essential feature or element of any or all the claims. 
     Furthermore, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles. 
     Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements.