FAN5601 Datasheet, PDF (11/14 Pages) Fairchild Semiconductor – Regulated Step-Down Charge Pump DC/DC Converter

FAN5601
Switch Configuration
V_IN
S1
C+
S2
C
B
VOUT
S3
C-
S4
C
OUT
PRODUCT SPECIFICATION
V_IN
S1
C+
S2
VOUT
CB
S3
C-
S4
C
OUT
GND
Figure 1. (A)
2:1 configuration
Switches in charging phase
Reverse all switches for pumping phase
GND
Figure 1. (B)
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
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 1µA. 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.
REV. 1.0.4 4/4/05
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