Abstract:
A charge pump system and method that may provide large supply voltages and currents with reduced ripple voltage at reduced ripple frequency. The charge pump system may include an array of charge pumps and a delay pipeline. The array of charge pumps may include a plurality of charge pumps. The delay pipeline may include a plurality of delay elements. The delay elements may respond to a global trigger signal to output a trigger signal to the array of charge pumps. Respective charge pumps may fire in response to the trigger signal.

Description:
PRIORITY 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/454,744 filed on Mar. 21, 2011, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    Charge pumps are well known devices. In integrated circuit (IC) implementations, components on the IC may have voltage or current requirements that differ from supply voltage or current sources supplied to the IC. Charge pumps may be used to convert the supplied current or voltage to a different voltage or current from the IC supply voltage. This is beneficial because it reduces customer cost, and power requirements for the IC. Charge pumps can be used to create supplies greater or less than the supply voltage or negative supplies generated from positive supply voltages. 
       BACKGROUND 
       [0003]    However, at times a large voltage or current value may be required for a particular application. This is typically accomplished using a large capacitor or inductor external to the IC. Commonly, as the voltage and current outputs rise, the respective noise also rises. In addition, as loads to the IC change, the voltage droop may become excessive due to the large voltages and/or currents being provided. Alternatively, fluctuation, or more commonly, “ripple”, in the output current or voltage value may be significant. If the ripple is significant, it can cause errors in the loads supplied with the output voltages or currents. The rate of change of the ripple voltage is the ripple frequency. 
         [0004]    One known method of reducing voltage or current ripple is to interleave a number of charge pumps. The number of charge pumps maintains the output voltage or current supply as each charge pump discharges and recharges according to a clock signal. Interleaving requires a number of clock signals to control the firing of the number of charge pumps. The firing of the number of charge pumps may actually increase the voltage ripple as each individual charge pump fires imprecisely due to failure to synchronize the number of clock signals. The management of the number of different clock signals requires a complex control device. Furthermore, the additional clock inputs and related connections also consume additional real estate on the IC, which increases cost as well as makes for a larger IC. Also, interleaving may not provide a large voltage or current that may be needed by a particular circuit application or configuration. 
         [0005]    Accordingly, there is a need for a charge pump configuration that supplies large voltage or current without the complex control and multitude of inputs of an interleaved solution. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  illustrates a block diagram of an exemplary charge pump system according to an embodiment of the present invention. 
           [0007]      FIG. 2  illustrates a charge pump system for randomized firing of charge pumps in a charge pump array according to an embodiment of the present invention. 
           [0008]      FIG. 3  illustrates a charge pump system for randomizing delays in supplying firing signals to charge pumps according to an embodiment of the present invention. 
           [0009]      FIG. 4  illustrates an exemplary charge pump for implementing an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    A charge pump system may include a plurality of charge pumps connected in an array, and a plurality of delay elements also connected in an array. A respective one of the delay elements connected to an enabling input of a respective one of the plurality of charge pumps. The respective delay elements may be supplied with a trigger signal according to which the charge pumps may be enabled to fire in a cascaded manner after some time delay to separately output a voltage to a common output connection of the plurality of charge pumps. The trigger signal supplied to the delay elements may be a single one-time input signal, or a single clock signal. The trigger signal may repeat only after all of the charge pumps have provided an output signal. 
         [0011]      FIG. 1  is a block diagram of a charge pump system according to an embodiment of the present invention. The charge pump system  100  may include a plurality of charge pumps  110 . 1  to  110 .N, a delay pipeline  120  and an input signal, which may be a trigger signal TRG. The charge pumps  110 . 1  to  110 .N may have outputs connected in parallel, and may generate a voltage and/or current signal to a load. 
         [0012]    The delay pipeline  120  may have an input to receive the trigger signal TRG. The trigger signal TRG may be a periodic clock signal, a single impulse signal (e.g., a “one-shot”), or any form of signal suitable to initiate the firing of the charge pumps  110 . 1  to  110 .N. The delay pipeline  120  may include a plurality of outputs  120 . 1  to  120 .N for outputting a firing signal output from respective delay elements  130 . 0  to  130 .N−1 to each of the respective charge pumps  110 . 1  to  110 .N. For example, the delay elements  130 . 0  to  130 .N−1 may be connected in series to provide incremented delay to the input global trigger signal TRG. As a result, the delayed trigger signal (e.g., TRG 1 , TRG 2  . . . ) may be offset from each other by a time period (at). The charge pumps  110 . 1  to  110 .N may be characterized by a decay time that is longer than a delay time of the delay elements  130 . 0  to  130 .N−1. In other words, the output voltage or current may overlap for a time period from each charge pump  110 . 1  to  110 .N as each charge pump fires. As a result, the output voltage or current may remain substantially constant. 
         [0013]    The delay elements  130 . 0  to  130 .N may be implemented using inverters, switches, delay lines or other circuit components (e.g., RC delay). For example, a single inverter has an inherent delay in the transistor switching of the inverter; the delay elements  130 . 0 - 130 .N−1 each may be made of one or more inverters. When the system  100  is fabricated as an integrated chip, the inverters will share common circuit characteristics, and hence a similar time delay. 
         [0014]    The delay elements  130 . 0  to  130 .N−1 may be configured either in an open loop configuration as shown, or as a ring oscillator. The cascaded delay elements  130 . 0  to  130 .N−1 may be arranged, for example, individually in series, or in groups of delay elements. Each delay element  130 . 0  to  130 .N−1 may provide the same delay period of Δt. 
         [0015]    During operation, the global trigger signal TRG may be applied to the input to the delay pipeline  120 . In response to the application of global trigger signal TRG, a trigger signal TRG 1  may be output from delay element  130 . 0  of the delay pipeline  120  via the output  120 . 1 . After a predetermined delay (Δt) due to delay element  130 . 0 , the timing signal TRG 1  may cause the first charge pump  110 . 1  to fire, and output a signal V OUT . The timing signal TRG 1  may be applied to delay element  130 . 1 , and, after a predetermined delay (at), output a trigger signal TRG 2  from the output  120 . 2  of the delay pipeline  120 . The trigger signal TRG 2  may now be delayed a time period of 2Δt from the initial application of the global trigger signal TRG to the delay pipeline  120 . The output  120 . 2  may provide the output trigger signal TRG 2  to the charge pump  110 . 2  and to delay element  130 . 2 . The charge pump  110 . 2  may fire in response to the trigger signal TRG 2 , and output a signal V OUT . The delay element  130 . 2  may also respond to the output signal from delay element  130 . 1  and after an inherent delay, output a trigger signal TRG 3  via delay pipeline output  120 . 3  to the charge pump  110 . 3  and to delay element  130 . 3 . As a result, charge pump  110 . 3  may fire and output a signal V OUT , and delay element  130 . 3  may output a trigger signal after a delay an output signal. This process may continue until delay element  130 .N−1 outputs delayed signal TRGN, which is output from delay pipeline output  120 .N to charge pump  110 .N. The charge pump  110 .N may fire in response to the trigger signal TRGN, and output a signal V OUT . 
         [0016]    Operation of the charge pump system  100  may be arranged such that all of the charge pumps  110 . 1  to  110 .N fire within one clock cycle, or some other predetermined period of time. In certain embodiments, the charge pumps  110 . 1  to  110 .N may be characterized by a decay time that is longer than a delay time of the delay elements  130 . 1 - 130 N−1. With this configuration and timing for the firing of each respective charge pump, a voltage, or current, of sufficient magnitude can be supplied to the load with minimal ripple and substantially no droop. If the delay elements  130 . 1  to  130 .N−1 are arranged in a ring oscillator configuration, the above sequence may repeat until interrupted by another control signal, for example. 
         [0017]    In certain situations, the delay elements and charge pumps may not provide consistent performance from one delay element to the next, or one charge pump to the next for various reasons. If the non-consistent performance occurs at a regular interval, it may generate an error that may be propagated upstream, and may, perhaps, be amplified. As a result, errors may occur at the output of the charge pump system. Different techniques may be applied to mitigate the potential for these types of errors to occur. For example, a first technique may be to randomize the selection a respective charge pump to be fired, and a second may be to randomize the delay applied to the firing signals applied to respective charge pumps. 
         [0018]    In the embodiment illustrated in  FIG. 2 , the firing of the charge pumps in a charge pump array  230  may be randomized by randomly selecting which charge pump to fire. The phased array charge pump system  200  may include a delay pipeline  210 , a routing system  220 , and a charge pump array  230 . The delay pipeline  210  may include a plurality of delay elements D 0 -DN, inputs for a trigger signal TRG and a delay bias signal BIAS, and outputs for delayed trigger signals TRG 1 -TRGN. The delay bias signal BIAS may be used to adjust the delay of the delay elements D 0 -DN in the delay pipeline  210 . The routing system  220  may include a plurality of multiplexors (MUX)  220 . 1 - 220 .N, an input for a routing control signal RC, a plurality of inputs to receive delayed trigger signals output from the delay pipeline  210 , and a plurality of outputs to pass the delayed trigger signals TRG 1 ′ to TRGN′ to a charge pump within the charge pump array  230 . 
         [0019]    The delay pipeline  210  may include inputs for a timing signal TRG and a bias signal BIAS. The timing signal TRG may begin the firing sequence for the charge pump array  230 . The bias signal BIAS may be applied to the delay elements D 0 -DN to adjust the delay of each delay element D 0 -DN. For example, the bias signal BIAS may be applied to a back gate of transistor used in an inverter implementation of the delay element D 0 -DN. Although shown as a single delay signal, each delay element D 0 -DN could have an individual bias signal applied to it. The choice of a particular bias level may be randomized. The delay pipeline  210  may be coupled to routing system  220 . Routing system  220  may have inputs for signals TRG 1 -TRGN output from the delay pipeline  210 , and an input for a routing control signal RC. The routing system  220  may be coupled to the charge pump array  230 . The routing system  220  may be configured to change the firing of the respective charge pumps from cycle to cycle to provide better error mitigation. 
         [0020]    In response to the TRG signal, the delay pipeline  210  may sequentially generate trigger signals TRG 1 -TRGN that are input to the routing system  220 . The routing system  220  may include a controller  225 , an input of a routing control RC signal, a plurality of inputs from the delay pipeline  210 , a plurality of outputs to the charge pump array  230 , logic devices  220 . 1 - 220 .N, which may be multiplexers. The routing control signal RC may be a digital code word. The controller  225  may interpret the digital code word and, based on the interpretation, route a trigger signal (e.g., TRG 1 ) to a respective charge pump in the charge pump array  230 . 
         [0021]    For example with reference to  FIG. 2 , the trigger signal TRG may be applied to the delay pipeline  210 . The delay element D 0  may apply a first delay, and output a delayed trigger signal TRG 1  to the routing system  220  and to delay element D 1 . The routing control signal RC may be applied to routing system  220 , and received by the controller  225 . Based on the interpretation of the routing control signal RC, the controller  225  may signal MUX  220 . 3  to pass delayed trigger signal TRG 1  and output randomized trigger signal TRG 3 ′ to a charge pump (not shown) connected to MUX  220 . 3  in charge pump  230 . Similarly, the delayed trigger signal TRG 2  output from delay element D 1  may passed by MUX  220 . 1 , which outputs randomized trigger signal TRG 1 ′. 
         [0022]    The routing control signal RC may be provided by an external or internal controller, and may change so charge pumps within the charge pump array  230  may fire sequentially or non-sequentially (i.e., randomized) to provide either a voltage or current signal. 
         [0023]      FIG. 3  shows a charge pump system that mitigates the potential for propagating signal errors according to another embodiment of the present invention. In the illustrated example, the delay of the firing of each of the individual charge pumps in a charge pump array may be randomized from cycle to cycle, thereby randomizing the effects of signal errors. The charge pump system  300  may include an array of charge pumps  310 . 1 - 310 .N, intermediate delay element  315  and a delay pipeline  320 . 
         [0024]    The cascaded delay elements  320 . 0 - 320 .N−1 may provide a delayed trigger signal from one delay element to the next. The time delay of each delay element  320 . 0 - 320 .N may be the same, or may be adjusted by application of a delay adjust signal, such as delay adjust X-0 to delay adjust X-N−1. Each delay element  320 . 0 - 320 .N−1 may have an individual delay adjustment that allows the delay for each delay element to be individually set. For example, in an implementation in which the delay elements  320 . 0 - 320 .N−1 are implemented using inverters, the delay of delay element  320 . 0  may be adjusted by applying the delay adjust X-0 signal to a back gate of a transistor in the inverter of delay element  320 . 0 . Alternatively, in a delay line implementation, the delay adjust X-0 signal may actuate a switch that adds or deletes additional delay line segments to the overall delay line. As shown, each delay element  320 . 0 - 320 .N−1 may have an individual delay adjust X-0—delay adjust X-N−1. The delay elements  320 . 0 - 320 .N−1 may be implemented using inverters, delay lines or RC circuits. 
         [0025]    The trigger signal TRG 1 -TRGN output from delay pipeline  320  may be input to intermediate delay  315 , which may be coupled to the delay pipeline  320  and to respective charge pumps  310 . 1  to  310 .N. The intermediate delay  315  may include delay elements  315 . 1  to  315 .N. The delay elements  315 . 1  to  315 .N may be implemented using inverters, delay lines or RC circuits. Similar to the delay elements  320 . 0 - 320 .N−1, each of the delay elements  315 . 1  to  315 .N may also have individual delay adjustments, such as delay adjust Y-0 to delay adjust Y-N−1. 
         [0026]    In operation, the global trigger signal TRG may be applied to the delay pipeline  320 . The delay element  320 . 0  may delay the global trigger signal TRG for a predetermined time delay based the delay element&#39;s  320 . 0  preset delay including any adjustment (increase or reduction) to the delay in response to the delay adjust X-0 signal. After the predetermined time delay, the delay element  320 . 0  may output a delayed trigger signal TRG 1  to intermediate delay  315  and to delay element  320 . 1 . The delayed trigger signal TRG 1  may be received at an input to intermediate delay element  315 . 1  of the intermediate delay  315 . After a preset delay (which may be individually adjusted by the delay adjust Y-1 signal), the intermediate delay element  315 . 1  may output a delayed trigger signal TRG 1 ″ for firing the charge pump  310 . 1 . In response to receiving the delayed trigger signal TRG 1 ″, the charge pump  310 . 1  may fire and output a voltage/current signal VOUT. The voltage/current signal VOUT may be provided to a load. With respect to the delayed trigger signal TRG 1  applied to delay element  330 . 1 , delay element  330 . 1  may further delay trigger signal TRG 1  for a predetermined time period including any delay adjustment in response to the delay adjust X-1 signal. Delay element  330 . 1  may output a delayed trigger signal TRG 2  to the intermediate delay  315  and to delay element  330 . 2 . The delayed trigger signal TRG 2  applied to intermediate delay  315  may be input to intermediate delay element  315 . 2 . Intermediate delay element  315 . 2  may delay outputting a trigger signal to charge pump  310 . 2  in response to its set delay including any adjustment (increase or reduction) to the delay in response to the delay adjust Y-1 signal. After the predetermined time period, the intermediate delay element  315 . 2  may output a delayed trigger signal TRG 2 ″ for firing the charge pump  310 . 2 . This process may continue for the firing of charge pumps  310 . 3 - 310 .N that may have delayed trigger signals TRG 3 ″-TRGN″ applied to them. 
         [0027]    The individual delay adjustments delay adjust Y-0 to delay adjust Y-N−1 signals may set the individual delays of the intermediate delay elements  315 . 1 - 315 .N. For example, the delay elements  315 . 1 - 315 .N may be implemented using transistors configured as inverters, and the respective delay adjust signal may be applied to a back gate of the respective transistors thereby effecting operation of the inverter and the inverter&#39;s delay. The plurality of different combinations of delay adjustment of the delay elements  320 . 0 - 320 .N−1 in the delay pipeline  320  with the delay adjustment of the delay elements  315 . 1 - 315 .N of the intermediate delay  315  provide numerous possibilities for overcoming the effects of erroneous signals in the signal chain. 
         [0028]      FIG. 4  illustrates an exemplary schematic diagram of a negative charge pump. A positive charge pump can be created by reconfiguring the switches and how they connect to VREF. The charge pump  400  may be used as one of the plurality of charge pumps as described with respect to  FIGS. 1-3 . The charge pump  400  may include a pair of switches  410 A and  410 B, a capacitor C 1 , an input for a control signal TRG, an input for reference voltage VREF, and an output for the output voltage VOUT. The charge pump  400  may be in a recharge state when control signal TRG is LOW, and switches  410 A and  410 B are connected to position φ 0 . Switch  410 A may be connected to reference voltage VREF and switch  410 B may be connected to a lower potential, or ground. As a result, capacitor C 1  may begin to charge to a voltage approximately equal to VREF. When the control signal TRG goes HIGH in response to an output from the respective delay elements, or routing logic, switches  410 A and  410 B are placed in a second position φ 1 . As a result, switch  410 A is connected to lower potential terminal, or ground, and switch  410 B is connected to the output VOUT. The capacitor C 1  discharges and outputs voltage/current signal VOUT. Once the control signal TRG is no longer asserted and goes LOW, the switch  410 A may re-connect to VREF and switch  41013  may re-connect to low potential, or ground, and capacitor C 1  may recharge. An inverter may be applied before control signal TRG to invert the sequence of operation. 
         [0029]    Several features and aspects of the present invention have been illustrated and described in detail with reference to particular embodiments by way of example only, and not by way of limitation. Those of skill in the art will appreciate that alternative implementations and various modifications to the disclosed embodiments are within the scope and contemplation of the present disclosure.