THV3543_Rev.1.00_E
ꢀ
Soft Start Circuit
Soft start function raises the output voltage gradually to prevent overshoot and inrush current at startꢀup. CHꢀ1, CHꢀ2
and Load Switch 1 circuit have internal soft start function. The output voltage of these internal soft start circuits rise
according to each internal startꢀup sequences. Accordingly, the output of DC/DC converter and the output after load
switch rise. Soft start operation is completed when these outputs have reached each regular voltage. Soft start time of
CHꢀ1, CHꢀ2 and Load Switch 1 are set to 10msec (See Figure 3).
ꢀ
Start-up Sequence
Figure 3 shows the waveform of startꢀup sequence. The device starts switching after normal startꢀup of CHꢀ1 and
CHꢀ2. VGL starts after normal startꢀup of CHꢀ1 output (VO1) and also when PANEL_EN pin is turned High level.
VGH starts with 5msec delay after startꢀup of Load Switch 1. Open drain pins, VO2_OK and VGH_OK, start after
normal startꢀup of CHꢀ2 and VGH respectively.
VGH
10msec
10msec
10msec 5msec
VO1
AVDD
LDO
(V_LDO=V_VGH)
VO2
3.3V
VGH_OK
VO2_OK
VGL
(PANEL_EN=High)
Figure 3. Startꢀup Sequence Waveforms
ꢀ
PANEL_EN
During the startꢀup operation of IC, VGL starts after normal startꢀup of CHꢀ1 output (VO1) and also when
PANEL_EN pin is turned High level. If Low level voltage is applied to PANEL_EN pin, VGL/Load Switch 1/VGH
stop operating. High level voltage is applied to VGL_ON pin again, operations after VGL are restarted.
If not in use, please connect to VREG5 pin.
THine Electronics, Inc.
Copyright© 2011 THine Electronics, Inc.
13/19
THINE [ THINE ELECTRONICS, INC. ]
