Rainbow Electronics MAX1685 User Manual
Page 7
MAX1684/MAX1685
Low-Noise, 14V Input, 1A, PWM
Step-Down Converters
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7
Pin Description
Typical Operating Characteristics (continued)
(Circuit of Figure 1, T
A
= +25°C, unless otherwise noted.)
V
IN
5V/div
0V
V
OUT
100mV/div
2ms/div
LINE-TRANSIENT RESPONSE
MAX1684/85 toc19
MAX1684, I
LOAD
= 100mA, V
IN
= 5V TO 10V,
SYNC/PWM = 3.3V
V
SHDN
5V/div
I
IN
50mA/div
10ms/div
STARTUP CURRENT
MAX1684, I
LOAD
= 100mA, V
OUT
= 3.3V,
V
IN
= 5V, C
ILIM/SS
= 0.1
µF, SYNC/PWM = 3.3V
MAX1684/85 toc20
PIN
High-Side MOSFET Gate Bias. Bias voltage for P-channel switch. Bypass to IN with a 0.1µF capacitor.
CVH
1
FUNCTION
NAME
Analog Supply Voltage Input. Connect to IN with a 0.2in metal trace. Bypass to PGND with a 0.1µF
capacitor.
AIN
2
Logic Supply Voltage Output and IC Logic Supply. Sources 5mA for external loads. Bypass to AGND
with 1µF capacitor.
CVL
4
Supply Voltage Input
IN
3
Reference Output. 1.25V reference output supplies 10µA for external loads. Bypass to AGND with 0.1µF
capacitor.
REF
6
Integrator Capacitor Connection. Connect a 0.01µF capacitor to AGND.
CC
8
Dual-Mode Feedback Input. Connect FB to V
OUT
for 1.25V output. Connect to an external resistor divider
to adjust the output voltage. Connect to AGND to set output voltage to 3.3V.
FB
7
Analog Ground
AGND
5
Current-Limit Adjust/Soft-Start Input. See the Current Limit and Soft-Start section.
ILIM/SS
10
Bootstrap Input. Connection for the bootstrap switch and internal feedback path. Connect BOOT to V
OUT
for V
OUT
< 5.5V. Connect BOOT to AGND for V
OUT
> 5.5V.
BOOT
12
Standby Control Input. Connect to CVL for normal operation. Connect to AGND for low-power mode
(Table 1). This pin overrides SYNC/PWM setting.
STBY
11
Active-Low Shutdown Input. Connect to ground for shutdown. SHDN can withstand the input voltage.
SHDN
15
Power Ground
PGND
16
Inductor Connection. Drain for internal P-channel MOSFETs. Connect inductor from LX to OUT.
LX
13, 14
SYNC/PWM Input:
For synchronized-PWM operation, drive with TTL level, 50% square wave.
Connect to CVL for PWM mode.
Connect to AGND for normal mode.
SYNC/PWM
9