19-1353; Rev 0; 4/98
MAX685 Evaluation Kit
____________________________Features
o
+15V Positive Output Voltage
o
-7.5V Negative Output Voltage
o
2.7V to 5.5V Battery Input Voltage
o
10mA Output Current
o
Single Inductor for Both Outputs
o
0.1µA Shutdown Current
o
200kHz or 400kHz Fixed Frequency
o
Power-OK Output
o
Surface-Mount, Low-Profile Components
o
Fully Assembled and Tested
________________General Description
The MAX685 evaluation kit (EV kit) provides dual-output
+15V and -7.5V voltages from 2.7V to 5.5V input volt-
age. Each output regulates separately, and each can
deliver 10mA output current. Both output voltages can
be adjusted by changing the feedback resistor values.
The MAX685 EV kit provides low quiescent current and
high efficiency for maximum battery life. The EV kit
operates at a fixed 200kHz or 400kHz frequency, which
allows the use of a tiny surface-mount inductor. This EV
kit is a fully assembled and tested surface-mount circuit
board.
Evaluates: MAX685
Component List
DESIGNATION QTY
C1
1
DESCRIPTION
10µF, 10V tantalum capacitor
Sprague 595D106X0010A2T or
AVX TAJA106K010R
2.2µF, 25V ceramic capacitors (1206)
Marcon/United Chemi-Con
THCR30E1E225ZT
0.22µF ceramic capacitors
47pF ceramic capacitor
Open
0.5A, 20V Schottky diodes
Motorola MBR0520LT3
3-pin headers
22µH inductor
Murata LQH4N220K04M00 or
TDK NLC453232 220K
1.0MΩ, 1% resistor (1206)
90.9kΩ, 1% resistor (1206)
750kΩ, 1% resistor (1206)
124kΩ, 1% resistor (1206)
100kΩ, 5% resistor (1206)
MAX685EEE
Shunts
MAX685 PC board
MAX685 data sheet
_______________Ordering Information
PART
MAX685EVKIT
TEMP. RANGE
0°C to +70°C
IC PACKAGE
16 QSOP
C2, C3
C4, C5
C6
C7
D1, D2
JU1, JU2, JU3
L1
R1
R2
R3
R4
R5
U1
None
None
None
2
2
1
0
2
3
1
1
1
1
1
1
1
3
1
1
__________________Component Suppliers
SUPPLIER
AVX
Coilcraft
Dale-Vishay
Marcon/
United Chemi-Con
Motorola
Murata
Sprague
Sumida
TDK
Vishay/Vitramon
PHONE
(803) 946-0690
(847) 639-6400
(402) 564-3131
(847) 696-2000
(602) 303-5454
(814) 237-1431
(603) 224-1961
(847) 956-0666
(847) 390-4373
(203) 268-6261
FAX
(803) 626-3123
(847) 639-1469
(402) 563-6418
(847) 696-9278
(602) 994-6430
(814) 238-0490
(603) 224-1430
(847) 956-0702
(847) 390-4428
(203) 452-5670
Note:
Please indicate that you are using the MAX685 when con-
tacting these component suppliers.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
MAX685 Evaluation Kit
Evaluates: MAX685
_________________________Quick Start
The MAX685 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.
1) Connect a +2.7V to +5.5V power supply to the VIN
pad. Connect ground to the GND pad.
2) Connect voltmeters and loads, if any, to the +VOUT
and VOUT- pads.
3) Verify that the shunts are on JU1, JU2, and JU3
across pins 2 and 3.
4) Turn on the power supply and verify the positive
output voltage is +15V and the negative output is
-7.5V.
5) For other output voltages, refer to the
Setting the
Output Voltage
section in the MAX685 data sheet
for instructions on selecting the feedback resistors.
Table 1. Jumper JU1 Functions
SHUNT
LOCATION
1 and 2
SHDN
PIN
MAX685 OUTPUT
Shutdown mode,
+V
OUT
= 0,
V
OUT-
= 0
MAX685 enabled,
V
OUT
= +15V,
V
OUT-
= -7.5V
Connected to GND
2 and 3
Connected to VIN
Table 2. Jumper JU2 Functions
SHUNT
LOCATION
1 and 2
2 and 3
SYNC PIN
Connected to GND
Connected to VIN
FREQUENCY (kHz)
200
400
_______________Detailed Description
The MAX685 EV kit provides dual-output +15V and
-7.5V voltages from 2.7V to 5.5V input voltage. Each
output regulates separately and each can deliver 10mA
output current. Both output voltages can be adjusted
by changing the feedback-resistor values.
The EV kit minimizes total circuit size and cost by using
a single inductor for both output voltages. It operates at
a fixed 200kHz or 400kHz frequency and includes a
shutdown function and a power-OK output.
Table 3. Jumper JU3 Functions
SHUNT
LOCATION
1 and 2
SEQ PIN
POWER SEQUENCE
Negative output pow-
ers up before positive
output.
Positive output powers
up before negative
output.
Connected to GND
__________________Jumper Selection
The MAX685 EV kit features a shutdown mode that
reduces quiescent current to 0.1µA typical to preserve
battery life. The 3-pin header JU1 selects the shutdown
mode. Table 1 lists the selectable jumper options.
The 3-pin header JU2 selects the switching frequency.
Table 2 lists the selectable jumper options. The 3-pin
header JU3 selects the power sequence. Table 3 lists
the selectable jumper options.
2 and 3
Connected to VIN
2
_______________________________________________________________________________________
MAX685 Evaluation Kit
Evaluates: MAX685
VOUT-
-7.5V
C3
2.2µF
25V
D1
MBR0520L
L1
22µH
D2
MBR0520L
+VOUT
+15V
C2
2.2µF
25V
VIN
2.7V TO 5.5V
C4
0.22µF
C1
10µF
10V
8
3
2
V
DD
VP
I.C.
LXN
16
PGND
R3
750k
1%
1
LXP
14
R1
1.0M
1%
C7
OPEN
10
R4
124k
1%
REF
1.25V
VIN
3
SHDN
JU1
2
1
3
SYNC
VIN
3
SEQ
JU3
2
1
VIN
JU2
2
1
C5
0.22µF
6
11
FBN
PGND
13
JU4
U1
MAX685
R2
90.9k
1%
REF
FBP
12
R5
100k
SHDN
POK
4
VIN
C6
47pF
POK
7
SYNC
GND
9
15
5
SEQ
I.C.
Figure 1. MAX685 EV Kit Schematic
_______________________________________________________________________________________
3
MAX685 Evaluation Kit
Evaluates: MAX685
1.0"
Figure 2. MAX685 EV Kit Component Placement Guide—
Component Side
1.0"
Figure 3. MAX685 EV Kit PC Board Layout—Component Side
1.0"
Figure 4. MAX685 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
© 1998 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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