MAX8795A Maxim Integrated Products, MAX8795A Datasheet - Page 19

• Manufacturer Part Number: MAX8795A
• Description: TFT-LCD DC-DC Converter
• Manufacturer: Maxim Integrated Products

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Figure 6. Power-Up Sequence
Figure 7. Switch-Control Block
VOLTAGE
INPUT
OK
2.25V
BEGINS
SOFT-
START
DEL
CTL
IN
12ms
1.05V
START
SOFT-
ENDS
REF
______________________________________________________________________________________
5µA
CONTROL
ENABLED
SWITCH
1.25V
TFT-LCD DC-DC Converter with
V
V
V
V
V
V
IN
REF
MAIN
GON
GOFF
DEL
1.25V (typ), the switch-control block is enabled as
shown in Figure 6. After the switch-control block is
enabled, COM can be connected to SRC or DRN
through the internal p-channel switches, depending
upon the state of CTL. Before startup and when IN is
less than V
to discharge C
using the following equation:
The switch-control input (CTL) is not activated until all
four of the following conditions are satisfied: the input
voltage exceeds V
regulators is complete, there is no fault condition detect-
ed, and V
vated and if CTL is high, the 5Ω internal p-channel
switch (Q1) between COM and SRC turns on and the
30Ω p-channel switch (Q2) between DRN and COM
turns off. If CTL is low, Q1 turns off and Q2 turns on.
Operational Amplifiers
DEL
2.25V
FB OK
FBP OK
FBN OK
UVLO
C
exceeds its turn-on threshold. Once acti-
DEL
DEL
, DEL is internally connected to AGND
UVLO
. Select C
=
MAX8795A
DELAY TIME
, the soft-start routine of all the
Q1
Q2
Switch-Control Block
_
DEL
to set the delay time
×
1 25
5
.
µ
A
V
SRC
COM
DRN
19