Datasheet

Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
IN
= 3.3V, V
MAIN
= 9V, V
G_ON
= 20V, V
G_OFF
= -7V, V
LOGIC
= 2.5V, V
GAMMA
= 8.6V, T
A
= +25°C,
unless otherwise noted.)
MAX1997/MAX1998
Quintuple/Triple-Output TFT LCD Power Supplies
with Fault Protection and VCOM Buffer
10 ______________________________________________________________________________________
OVERCURRENT PROTECTION RESPONSE
TO OVERLOAD DURING STARTUP
MAX1997 toc20
20ms/div
B
A
C
0
10V
-10V
10V
20V
0
5V
A: V
MAIN
, 5V/div
B: V
GATE
, 5V/div
C: V
G_ON
, 10V/div
D: V
G_OFF
, 10V/div
D
0
5V
OVERCURRENT PROTECTION RESPONSE
TO OVERLOAD DURING NORMAL OPERATION
MAX1997 toc21
20ms/div
B
A
C
0
10V
-10V
10V
20V
0
5V
A: V
MAIN
, 5V/div
B: V
GATE
, 5V/div
C: V
G_ON
, 10V/div
D: V
G_OFF
, 10V/div
D
0
5V
REFERENCE VOLTAGE
vs. LOAD CURRENT
MAX1997 toc22
LOAD CURRENT (µA)
REFERENCE VOLTAGE (V)
10
1.247
1.248
1.249
1.250
1.246
1 100
LX CURRENT LIMIT vs. INPUT VOLTAGE
MAX1997 toc23
INPUT VOLTAGE (V)
CURRENT LIMIT (A)
5.04.54.03.53.0
1.8
1.9
2.0
2.1
2.2
1.7
2.5 5.5
T
A
= -40°C
T
A
= +25°C
T
A
= +85°C
VCOM BUFFER TRANSCONDUCTANCE
vs. TEMPERATURE
MAX1997 toc24
TEMPERATURE (°C)
TRANSCONDUCTANCE (S)
806040200-20
2
4
6
8
10
0
-40 100
LARGE-SIGNAL
TRANSCONDUCTANCE
SMALL-SIGNAL
TRANSCONDUCTANCE
VCOM LOAD TRANSIENT RESPONSE
(CIRCUIT OF PAGE 6, NOTE 4)
MAX1997 toc25
4µs/div
B
A
C
0
1A
-20V
20V
3.4V
3.6V
0
A: LOAD CURRENT, 1A/div
B: V
OUTB
= 3.6V, 200mV/div, AC-COUPLED
C: V
X
, 20V/div
-1A
3.8V
PIN
MAX1997
MAX1998
NAME FUNCTION
1 —
TGNDB
Internal Connection. Connect this pin to ground. Do not leave this pin floating.
2 1 PGND
Power Ground. PGND is the source of the N-channel power MOSFET. Connect PGND to the
star ground at the device’s backside pad.
3 — DRV1
Logic Linear-Regulator (REG 1) Base Drive. Open drain of an internal N-channel MOSFET.
Connect DRV1 to the base of an external PNP linear regulator pass transistor. (See the Pass
Transistor Selection section).
Pin Description