FAN5601

PRODUCT SPECIFICATION

REV. 1.0.4 4/4/05

11

charge cycle. Full switch operation occurs only during star-

tup or under heavy load condition, when half switch opera-

tion cannot achieve regulation within seven charge cycles.

Soft Start

The soft-start feature limits inrush current when the device is

initially powered up and enabled. The reference voltage is

used to control the rate of the output voltage ramp-up to its

final value. Typical start-up time is 1ms. Since the rate of the

output voltage ramp-up is controlled by an internally gener-

ated slow ramp, pulse-skipping occurs and inrush current is

automatically limited.

Shutdown, UVLO, Short Circuit Current Limit

and Thermal Shutdown

The device has an active-low shutdown pin to decrease sup-

ply current to less than 1

µA. In shutdown mode the supply is

disconnected from the output. UVLO triggers when supply

voltage drops below 2V. When the output voltage is lower

than 150mV, a short circuit protection is triggered. In this

mode 15 out of 16 pulses during the switching will be

skipped and the supply current is limited. Thermal shutdown

triggers at 150ºC.

Switch Configuration

S1

S2

S3

S4

V

IN

GND

C+

VOUT

C-

C

OUT

2:1 configuration

Switches in charging phase

Reverse all switches for pumping phase

C

B

S1

S3

S4

V

IN

GND

C+

VOUT

C-

C

OUT

1:1 configuration

Switch 3 is always off and

Switch 4 is always on

Switches 1 and 2 are in phase 1

Reverse the position of switches 1&2

for phase 2

C

B

S2

Figure 1. (A)

Figure 1. (B)