19-1677; Rev 0; 4/00

MAX1698 Evaluation Kit

The MAX1698 evaluation kit (EV kit) is a fully assembled
and tested circuit board that contains a boost switching-regulator current source and array of white LEDs.
As configured, the circuit is set up to drive 3 banks of 3
series LED arrays at 20mA each; however, a wide variety of other configurations are possible. The IC can be
powered from a separate +2.7VDC to +5.5VDC input,
while LED power has a wider input range and can besupplied either from a logic supply or battery source.
The MAX1698 features digital soft-start and adjustable
lossless LED current control. The MAX1698 EV kit
demonstrates low quiescent current, open-circuit protection, and up to 90% efficiency for maximum battery
life. Operation up to 500kHz allows the use of tiny surface-mount components.

Features♦ Input Voltage Down to +0.8V♦ 3x3 White LED Array♦ Potentiometer-Adjustable Output Current Level(LED Brightness Control)♦ External Low-Loss N-Channel Switch♦ 10nA IC Shutdown Current♦ Operation Up to 500kHz Switching Frequency♦ Surface-Mount Components♦ Fully Assembled and Tested

Component List
DESIGNATION QTY

DESCRIPTION

C1110µF, 25V X5R ceramic cap (1812)
Taiyo Yuden TMK432BJ106KM

C211µF, 25V X5R ceramic cap (1206)
Taiyo Yuden TMK316BJ105KL or
Murata GRM42-6X7R105K025A

11µF, 6.3V X5R ceramic cap (0603)
Taiyo Yuden JMK107BJ105KA

140V, 0.5A Schottky diode (SOD-123)
Motorola MBR0540T1 or
Nihon EP05Q04

C3D1

124V, 350mW zener diode (SOT-23)
Central Semiconductor CMPZ5253B

D3–D119White LEDs
Nichia NSPW500BS (T-1-3/4)

L1

110µH inductor
Sumida CDRH5D18-100NC

N1

130V, 2.2A, N-channel MOSFET(SuperSOT™-3)
Fairchild Semiconductor FDN337N

R11500kΩ potentiometer
Bourns 3352E-1-504

R2, R3, R4315Ω ±1% resistors (0805)

U1

1MAX1698EUB (10-pin µMAX)

D2JU113-pin header

None

1Shunt (JU1)

None

1

MAX1698 PC board

None

1MAX1698 data sheet

None

1MAX1698 EV kit data sheet

Ordering Information
PART
MAX1698EVKITTEMP. RANGEIC PACKAGE

0°C to +70°C

10 µMAX

Component Suppliers
SUPPLIER

PHONEFAXCentralSemiconductor

516-435-1110

516-435-1824

Fairchild

408-822-2000

408-822-2102

Motorola602-303-5454

602-994-6430

Murata814-956-0666

847-238-0490

Nichia America
Corporation

408-573-0933

408-573-0934

Nihon USA661-867-2555

661-867-2698

Sumida708-956-0666

708-956-0702

Taiyo Yuden

408-573-4150

408-573-4159

Note: Please indicate that you are using the MAX1698 whencontacting these component suppliers.
SuperSOT is a trademark of Fairchild Semiconductor.

Quick Start
The MAX1698 EV kit is fully assembled and tested.
Follow these steps to verify board operation. Do notturn on the power supply until all connections arecompleted.

________________________________________________________________ Maxim Integrated Products

1For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.

Evaluates: MAX1698

General Description

Evaluates: MAX1698

MAX1698 Evaluation Kit
Main Output

Changing Maximum LED Current

1) Connect a +2.7V to +5.5V supply to the VCC pad.
Connect the ground to the GND pad.

The maximum LED current is determined by feedback
resistor R2. LED current = 300mV / R2. Resistors R3
and R4 must also match the value of R2 to balance thecurrent in each LED bank. Refer to the Setting theOutput Current section of the MAX1698 data sheet for
more information on selecting other maximum current
settings.

2) Connect a +0.8V to +7V supply to the VBATT pad.
Connect the ground to the GND pad.
3) Connect a voltmeter to the VOUT pad.
4) Verify that shunt JU1 (SHDN) is across pins 1 and 2.
5) Rotate the potentiometer (R1) to the midposition.
6) Turn on the power supply, and verify that the output
is approximately 9.0V and the LEDs are moderatelylit.
For instructions on selecting R1, or other means ofadjusting brightness, refer to the Adjusting LED Current
section in the MAX1698 data sheet.

Detailed Description
The MAX1698 EV kit contains a switching-regulator current-source circuit. The circuit requires +2.7V to +5.5V
for IC power (VCC); however, the LED power input(VBATT) can accept a wide input voltage range from+0.8V up to the forward voltage of the LED array (+7V
for the 3x3 array supplied on the EV kit). The board candrive up to +24V for the LED output, as limited by theopen-circuit protection zener (D2).
Output current is adjusted with R1 to control LED
brightness. The boost converter operates up to a maximum frequency of 500kHz.
The MAX1698 EV kit can evaluate additional off-board
LEDs. For instructions on evaluating additional LEDs,
see the Evaluating Off-Board LEDs section.

Evaluating Off-Board LEDs
The MAX1698 EV kit can evaluate off-board LEDs.
Current resistors R2, R3, and R4 must be removed fromthe EV kit. The EV kit LEDs will no longer function. An
external feedback resistor must be connected between
the FB pad and GND pad. Refer to the Setting theOutput Current section of the MAX1698 data sheet for
more information on selecting the maximum currentsetting resistor.

Evaluating Output Voltages Over +24V
Zener diode D2 clamps the output voltage VOUT at+24V if the LED array circuit opens. To evaluate output
voltages greater than +24V, zener diode D2 must bereplaced. Choose the zener diode +2V above the maximum V OUT . The MOSFET N1 breakdown voltage
should exceed the zener voltage. Output capacitor
C2’s voltage rating must exceed the zener diode voltage.

Table 1. Jumper JU1 Functions
SHUNT
LOCATIONSHDN PIN

1 and 2Connected to VCC

MAX1698 enabled,
VOUT = up to +24V

2 and 3Connected to GND

Shutdown mode,
VOUT = VIN - VD1Jumper Selection Shutdown Mode
The MAX1698 EV kit features a shutdown mode that
reduces the MAX1698 quiescent current to less than
1µA (max), preserving battery life. The three-pin jumper(JU1) selects the shutdown mode for the circuit. Table
1 lists the selectable jumper options.

2MAX1698
OUTPUT_______________________________________________________________________________________

_______________________________________________________________________________________

SHDN

GND

VCC
+2.7V TO +5.5V

GND

C31µF
R1500k

C110µF
25V

123L110µH

5431U1GND

ADJ

REF

32JU12SHDN

1CSEXTFB

AGND

PGND

MAX1698EUB

VCC

678910N1D121R415Ω
1%R315Ω
1%R215Ω1%L

D224V ZENER

C21µF
25V

3D5D4

D3

D8

D7

D6

D11

D10

D9FB

GND

VOUT

Evaluates: MAX1698

VBATT+0.8V TO +7.0V

MAX1698 Evaluation Kit

Figure 1. MAX1698 EV Kit Schematic

3

Evaluates: MAX1698

MAX1698 Evaluation Kit

1.0"

1.0"

Figure 2. MAX1698 EV Kit Component Placement Guide—Component SideFigure 3. MAX1698 EV Kit PC Board Layout—Component Side

1.0"

Figure 4. MAX1698 EV Kit PC Board Layout—Solder Side

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses areimplied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

4 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600© 2000 Maxim Integrated Products

Printed USAis a registered trademark of Maxim Integrated Products.