THV3543 Datasheet, PDF (11/19 Pages) THine Electronics, Inc. – 2 channel Buck/Boost 2 channel Charge Pump Controller

THV3543_Rev.1.00_E
Functional Description
System UVLO
THV3543 has built-in UVLO (Under Voltage Lockout) circuit to prevent low-voltage input malfunction. The internal
specified threshold voltage is 3.5V, the release voltage is 5.46V. When input power supply voltage (Vin) reaches the
UVLO release voltage (5.46V), the device starts the soft start operation and output voltage (Vo) gradually rises up to
the regular voltage. When the input power supply voltage (Vin) drops below 3.5V, UVLO stops switching operation
immediately and starts discharging soft start. Accordingly, the output voltage (Vo) drops (See Figure 1).
5.46V
Vin _3.50V
switching
Operating
Stop
Operating
Stop
Vo
Figure 1. UVLO Operation Example
The UVLO threshold voltage also can be set optionally by applying divided Vin by an external resistance to
SYSUVLO pin (See Figure 2). Please use external resistance of enough lower value than the internal resistance. The
System UVLO threshold voltage is given by the following formulas.
System UVLO Release Voltage　= 1.56 × ^{R1 + R2}
R2
System UVLO Detection Voltage(Lower Limit Voltage of Operation)　= 1.0 × ^{R1 + R2}
R2
Vin
R1
R2
VCC
SYSUVLO
500k
UVLO
COMP
200k
Figure 2. System UVLO Setting Circuit
Copyright© 2011 THine Electronics, Inc.
11/19
THine Electronics, Inc.