19-1677; Rev 0; 4/00
MAX1698 Evaluation Kit
General Description
The MAX1698 evaluation kit (EV kit) is a fully assembled
and tested circuit board that contains a boost switch-
ing-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 vari-
ety 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 be
supplied 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 pro-
tection, and up to 90% efficiency for maximum battery
life. Operation up to 500kHz allows the use of tiny sur-
face-mount components.
o
Input Voltage Down to +0.8V
o
3x3 White LED Array
o
Potentiometer-Adjustable Output Current Level
(LED Brightness Control)
o
External Low-Loss N-Channel Switch
o
10nA IC Shutdown Current
o
Operation Up to 500kHz Switching Frequency
o
Surface-Mount Components
o
Fully Assembled and Tested
Features
Evaluates: MAX1698
Component List
DESIGNATION QTY
C1
1
DESCRIPTION
10µF, 25V X5R ceramic cap (1812)
Taiyo Yuden TMK432BJ106KM
1µF, 25V X5R ceramic cap (1206)
Taiyo Yuden TMK316BJ105KL or
Murata GRM42-6X7R105K025A
1µF, 6.3V X5R ceramic cap (0603)
Taiyo Yuden JMK107BJ105KA
40V, 0.5A Schottky diode (SOD-123)
Motorola MBR0540T1 or
Nihon EP05Q04
24V, 350mW zener diode (SOT-23)
Central Semiconductor CMPZ5253B
White LEDs
Nichia NSPW500BS (T-1-3/4)
10µH inductor
Sumida CDRH5D18-100NC
30V, 2.2A, N-channel MOSFET
(SuperSOT™-3)
Fairchild Semiconductor FDN337N
500kΩ potentiometer
Bourns 3352E-1-504
15Ω ±1% resistors (0805)
MAX1698EUB (10-pin µMAX)
3-pin header
Shunt (JU1)
MAX1698 PC board
MAX1698 data sheet
MAX1698 EV kit data sheet
PART
MAX1698EVKIT
Ordering Information
TEMP. RANGE
0°C to +70°C
IC PACKAGE
10 µMAX
C2
1
Component Suppliers
SUPPLIER
Central
Semiconductor
Fairchild
Motorola
Murata
Nichia America
Corporation
Nihon USA
Sumida
Taiyo Yuden
PHONE
516-435-1110
408-822-2000
602-303-5454
814-956-0666
408-573-0933
661-867-2555
708-956-0666
408-573-4150
FAX
516-435-1824
408-822-2102
602-994-6430
847-238-0490
408-573-0934
661-867-2698
708-956-0702
408-573-4159
C3
1
D1
1
D2
D3–D11
L1
1
9
1
N1
1
Note:
Please indicate that you are using the MAX1698 when
contacting these component suppliers.
SuperSOT is a trademark of Fairchild Semiconductor.
R1
R2, R3, R4
U1
JU1
None
None
None
None
1
3
1
1
1
1
1
1
Quick Start
The MAX1698 EV kit is fully assembled and tested.
Follow these steps to verify board operation.
Do not
turn on the power supply until all connections are
completed.
________________________________________________________________
Maxim Integrated Products
1
For 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.
MAX1698 Evaluation Kit
Evaluates: MAX1698
Main Output
1) Connect a +2.7V to +5.5V supply to the VCC pad.
Connect the ground to the GND pad.
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 moderately
lit.
For instructions on selecting R1, or other means of
adjusting brightness, refer to the
Adjusting LED Current
section in the MAX1698 data sheet.
Changing Maximum LED Current
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 the
current in each LED bank. Refer to the
Setting the
Output Current
section of the MAX1698 data sheet for
more information on selecting other maximum current
settings.
Evaluating Off-Board LEDs
The MAX1698 EV kit can evaluate off-board LEDs.
Current resistors R2, R3, and R4 must be removed from
the 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 the
Output Current
section of the MAX1698 data sheet for
more information on selecting the maximum current-
setting resistor.
Detailed Description
The MAX1698 EV kit contains a switching-regulator cur-
rent-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 can
drive up to +24V for the LED output, as limited by the
open-circuit protection zener (D2).
Output current is adjusted with R1 to control LED
brightness. The boost converter operates up to a maxi-
mum 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 Output Voltages Over +24V
Zener diode D2 clamps the output voltage V
OUT
at
+24V if the LED array circuit opens. To evaluate output
voltages greater than +24V, zener diode D2 must be
replaced. Choose the zener diode +2V above the maxi-
mum 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
LOCATION
1 and 2
2 and 3
SHDN
PIN
Connected to VCC
Connected to GND
MAX1698
OUTPUT
MAX1698 enabled,
V
OUT
= up to +24V
Shutdown mode,
V
OUT
= V
IN
- V
D1
Jumper 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.
2
_______________________________________________________________________________________
VBATT
+0.8V TO +7.0V
L1
10µH
D1
VOUT
D3
D6
D9
Figure 1. MAX1698 EV Kit Schematic
C1
10µF
25V
C2
1µF
25V
GND
1
VCC
GND
VCC
+2.7V TO +5.5V
U1
9
D5
8
7
6
1
L
3
2
D8
EXT
D4
D7
D10
10
N1
GND
3
REF
ADJ
GND
FB
SHDN
2
AGND
D2
24V ZENER
PGND
CS
C3
1µF
R1
500k
1
5
2
4
3
MAX1698EUB
D11
3
JU1
2
1
R2
15Ω
1%
R3
15Ω
1%
R4
15Ω
1%
FB
Evaluates: MAX1698
_______________________________________________________________________________________
SHDN
MAX1698 Evaluation Kit
3
MAX1698 Evaluation Kit
Evaluates: MAX1698
1.0"
1.0"
Figure 2. MAX1698 EV Kit Component Placement Guide—
Component Side
Figure 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 are
implied. 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 USA
is a registered trademark of Maxim Integrated Products.
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