19-1454; Rev 0; 4/99
MAX1685 Evaluation Kit
General Description
The MAX1685 evaluation kit (EV kit) is a fully assembled
and tested surface-mount circuit board that contains a
pulse-width-modulated (PWM), step-down DC-DC con-
verter. The EV kit provides a +3.33V output voltage
from a +3.5V to +14V input source. It delivers up to 1A
output current. The MAX1685 features internal MOSFET
switches, low dropout voltage (100% duty-cycle opera-
tion), and an accurate +1.25V reference.
The MAX1685 EV kit provides low quiescent current,
synchronous rectification, and high efficiency (up to
95%) for maximum battery life. Operation at 600kHz
allows the use of a tiny surface-mount inductor.
The MAX1685 EV kit can also be used to evaluate the
MAX1684, which operates at 300kHz and has slightly
higher efficiency than the MAX1685.
o
+3.5V to +14V Input Voltage Range
o
Fixed or Adjustable Output Voltage
+3.33V (Fixed)
+1.25V to V
IN
(Adjustable)
o
Guaranteed 1A Output Current
o
100% Duty Cycle in Dropout
o
600kHz Fixed-Frequency PWM Operation
o
Internal MOSFET Switch and Synchronous
Rectifier
o
2µA IC Shutdown Current
o
Surface-Mount Components
o
Fully Assembled and Tested
Features
Evaluates: MAX1684/MAX1685
Component List
DESIGNATION QTY
C1
1
DESCRIPTION
22µF, 35V tantalum capacitor
AVX TPSE226M035R0300 or
Sprague 593D226X0035E2T
100µF, 10V, low-ESR tantalum capacitor
AVX TPSD107M010R0080,
Sprague 594D107X0010C2T, or
Sanyo 10TPB100M
0.1µF ceramic capacitors
0.01µF ceramic capacitor
1µF, 16V X7R ceramic capacitor
Taiyo Yuden EMK316BJ105KL or
TDK C3216X7R1C105M
Not installed
1A Schottky diode
Motorola MBRS130LT3,
International Rectifier 10BQ040,
Nihon EC10QS03, or Nihon EP10QY03
10µH inductor
Sumida CDRH6D28-100NC or
Sumida CDRH73-100
Not installed
100kΩ 5% resistors
MAX1685EEE
3-pin header
2-pin headers
Shunt (JU1)
MAX1684/MAX1685 PC board
MAX1684/MAX1685 data sheet
SUPPLIER
AVX
Dale-Vishay
International
Rectifier
Motorola
Nihon
Sanyo
Sprague
Sumida
TDK
Taiyo Yuden
Ordering Information
PART
MAX1685EVKIT
TEMP. RANGE
0°C to +70°C
IC PACKAGE
16-QSOP
C2
1
Note:
To evaluate the MAX1684, request a MAX1684EEE free
sample with the MAX1685 EV kit.
C3, C4, C5, C9
C6
C7
C8
4
1
1
0
Component Suppliers
PHONE
803-946-0690
402-564-3131
310-322-3331
602-303-5454
661-843-7500
619-661-6835
603-224-1961
708-956-0666
847-390-4373
408-573-4150
FAX
803-626-3123
402-563-6418
310-322-3332
602-994-6430
661-843-2798
619-661-1055
603-224-1430
708-956-0702
847-390-4428
408-573-4159
D1
1
L1
R1, R2
R3, R4
U1
JU1
JU2, JU3
None
None
None
1
0
2
1
1
2
1
1
1
Note:
Please indicate that you are using the MAX1685 when
contacting these component suppliers.
1
________________________________________________________________
Maxim Integrated Products
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX1685 Evaluation Kit
Evaluates: MAX1684/MAX1685
Quick Start
The MAX1685 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 +3.5V to +14V supply to the VIN pad.
Connect ground to the GND pad.
2) Connect a voltmeter and load (if any) to the VOUT
pad.
3) Verify that the shunt is across JU1 pins 1 and 2.
4) Turn on the power supply and verify that the output
is at +3.33V.
Operating Mode
The MAX1685 operates in one of four modes to opti-
mize performance: a fixed-frequency (PWM) mode
switches at a fixed frequency for easy postfiltering; a
low-power standby mode; a synchronizable PWM mode
that uses an external clock to minimize harmonics; and
a normal mode that extends battery life by operating in
PWM mode under heavy loads and PFM mode under
light loads to reduce power consumption.
Table 1. Jumper JU1 Functions
SHUNT
LOCATION
1&2
SHDN
PIN
Connected to VIN
Connected to GND
MAX1685
OUTPUT
MAX1685 enabled,
V
OUT
= +3.33V
Shutdown mode,
V
OUT
= 0
Detailed Description
Jumper Selection
Shutdown Mode
The MAX1685 EV kit features a shutdown mode that
reduces the MAX1685’s quiescent current to 2µA, pre-
serving battery life. The 3-pin header, JU1, selects the
shutdown mode (Table 1).
2&3
3.5V TO 14V
VIN
C1
22µF
35V
3
IN
AIN
LX
15
SHDN
PGND
1
CVH
C3
0.1µF
LX
13
14
16
L1
10µH
C2
100µF
10V
VOUT
1
2
3
V
OUT
+3.33V
2
VIN
SHDN
JU2
VL
SYNC/PWM
VL
STBY
JU3
9
R3
100kΩ
R4
100kΩ
C4
0.1µF
10
C5
0.1µF
8
11
6
C9
0.1µF
D1
1
JU1 2
3
U1
MAX1685
SYNC/PWM BOOT 12
JU4
STBY
REF
7
C8
OPEN
R1
OPEN
FB
ILIM/SS
CC
AGND
5
CVL
4
C7
1µF
16V
VL
R2
SHORT
(PC TRACE)
C6
0.01µF
Figure 1. MAX1685 EV Kit Schematic
2
_______________________________________________________________________________________
MAX1685 Evaluation Kit
The EV kit operates at 600kHz switching frequency and
allows the use of a tiny inductor. The switching frequen-
cy can also be synchronized to an external clock rang-
ing from 360kHz to 700kHz. The 2-pin headers JU2 and
JU3 select the operating mode (Tables 2 and 3).
4.7pF capacitor at location C8. For output voltages
greater than +5.5V, cut the trace between pins 1 and 2
of JU4, and short pins 2 and 3 of JU4. Refer to the
Detailed Description
section of the MAX1684/
MAX1685 data sheet for further details.
Evaluates: MAX1684/MAX1685
Evaluating Other Output Voltages
The EV kit output is preset to +3.33V. However, the out-
put voltage can also be adjusted between 1.25V and
V
IN
by selecting R1 and R2 values. Select feedback
resistor R2 in the 20kΩ to 100kΩ range. R1 is then
given by:
R1 = R2 [(V
OUT
/ V
FB
) - 1]
where V
FB
= 1.25V. Be sure to cut the PC trace shorting
the pads of R2 before installing the resistor. Install a
Evaluating the MAX1684
This EV kit can also be used to evaluate the MAX1684.
Simply replace the MAX1685 with a MAX1684EEE, and
change L1 to a 22µH, 1.7A inductor. Refer to the
Inductor Selection
section of the MAX1684/MAX1685
data sheet for more information.
Table 2. Jumper JU2 Functions
SHUNT
LOCATION
On
SYNC/PWM PIN
Connected to VL
Connected to GND
Off
(not installed)
OPERATING MODE
MAX1685 operates in
fixed-frequency mode.
MAX1685 operates in
normal mode.
SYNC/PWM pin is
driven by an external
clock between 360kHz
and 700kHz.
Table 3. Jumper JU3 Functions
SHUNT
LOCATION
On
STBY
PIN
Connected to VL
OPERATING MODE
Operation depends on
the JU2 setting.
MAX1685 operates in
low-power mode. This
overrides the JU2
setting.
Off
(not installed)
Connected to GND
Driven from
external clock
_______________________________________________________________________________________
3
MAX1685 Evaluation Kit
Evaluates: MAX1684/MAX1685
1.0"
Figure 2. MAX1685 EV Kit Component Placement Guide—
Component Side
1.0"
Figure 3. MAX1685 EV Kit PC Board Layout—Component Side
1.0"
Figure 4. MAX1685 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
© 1999 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
微控制器 MCU
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
