________________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.
____________________________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
0.1A Shutdown Current
o
200kHz or 400kHz Fixed Frequency
o
Power-OK Output
o
Surface-Mount, Low-Profile Components
o
Fully Assembled and Tested
Evaluates: MAX685
MAX685 Evaluation Kit
________________________________________________________________
Maxim Integrated Products
1
QTY
DESCRIPTION
C1
1
C2, C3
2
C4, C5
2
0.22F ceramic capacitors
C6
1
C7
0
Open
D1, D2
2
JU1, JU2, JU3
3
L1
1
R1
1
1.0M
, 1% resistor (1206)
R2
1
90.9k
, 1% resistor (1206)
R3
1
750k
, 1% resistor (1206)
R4
1
124k
, 1% resistor (1206)
R5
1
100k
, 5% resistor (1206)
47pF ceramic capacitor
2.2F, 25V ceramic capacitors (1206)
Marcon/United Chemi-Con
THCR30E1E225ZT
10F, 10V tantalum capacitor
Sprague 595D106X0010A2T or
AVX TAJA106K010R
SUPPLIER
PHONE
FAX
AVX
(803) 946-0690
(803) 626-3123
__________________Component Suppliers
DESIGNATION
0.5A, 20V Schottky diodes
Motorola MBR0520LT3
3-pin headers
22H inductor
Murata LQH4N220K04M00 or
TDK NLC453232 220K
Component List
_______________Ordering Information
Coilcraft
(847) 639-6400
(847) 639-1469
Dale-Vishay
(402) 564-3131
(402) 563-6418
Marcon/
United Chemi-Con
(847) 696-2000
(847) 696-9278
Motorola
(602) 303-5454
(602) 994-6430
Murata
(814) 237-1431
(814) 238-0490
PART
MAX685EVKIT
0C to +70C
TEMP. RANGE
IC PACKAGE
16 QSOP
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.
U1
1
MAX685EEE
None
3
Shunts
None
1
MAX685 PC board
None
1
MAX685 data sheet
Sprague
(603) 224-1961
(603) 224-1430
Sumida
(847) 956-0666
(847) 956-0702
TDK
(847) 390-4373
(847) 390-4428
Vishay/Vitramon
(203) 268-6261
(203) 452-5670
Note:
Please indicate that you are using the MAX685 when con-
tacting these component suppliers.
19-1353; Rev 0; 4/98
_________________________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.
_______________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.
__________________Jumper Selection
The MAX685 EV kit features a shutdown mode that
reduces quiescent current to 0.1A 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.
Evaluates: MAX685
MAX685 Evaluation Kit
2
_______________________________________________________________________________________
SHUNT
LOCATION
SHDN
PIN
MAX685 OUTPUT
1 and 2
Connected to GND
Shutdown mode,
+V
OUT
= 0,
V
OUT-
= 0
2 and 3
Connected to VIN
MAX685 enabled,
V
OUT
= +15V,
V
OUT-
= -7.5V
Table 1. Jumper JU1 Functions
SHUNT
LOCATION
SYNC PIN
FREQUENCY (kHz)
1 and 2
Connected to GND
200
2 and 3
Connected to VIN
400
SHUNT
LOCATION
SEQ PIN
POWER SEQUENCE
1 and 2
Connected to GND
Negative output pow-
ers up before positive
output.
2 and 3
Connected to VIN
Positive output powers
up before negative
output.
Table 2. Jumper JU2 Functions
Table 3. Jumper JU3 Functions
Evaluates: MAX685
MAX685 Evaluation Kit
_______________________________________________________________________________________
3
MAX685
U1
SYNC
SEQ
SHDN
REF
1.25V
V
DD
VP
I.C.
LXP
FBN
REF
SHDN
SEQ
POK
GND
I.C.
16
14
13
12
4
POK
9
15
5
SYNC
7
6
11
10
1
3
2
8
C5
0.22
F
R3
750k
1%
R4
124k
1%
C4
0.22
F
C3
2.2
F
25V
C1
10
F
10V
FBP
PGND
PGND
LXN
+VOUT
+15V
C2
2.2
F
25V
R1
1.0M
1%
C7
OPEN
VIN
2.7V TO 5.5V
VOUT-
-7.5V
D1
MBR0520L
D2
MBR0520L
JU4
L1
22
H
VIN
3
1
2
JU1
VIN
3
1
2
JU3
VIN
VIN
R5
100k
R2
90.9k
1%
C6
47pF
3
1
2
JU2
Figure 1. MAX685 EV Kit Schematic
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.
Evaluates: MAX685
MAX685 Evaluation Kit
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.
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
1.0"
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