Datasheet

MAX1997/MAX1998
Quintuple/Triple-Output TFT LCD Power Supplies
with Fault Protection and VCOM Buffer
_______________________________________________________________________________________ 7
Typical Operating Characteristics
(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.)
STEP-UP REGULATOR EFFICIENCY
vs. LOAD CURRENT (V
MAIN
= 9V)
MAX1997 toc01
LOAD CURRENT (mA)
EFFICIENCY (%)
10010
10
20
30
40
50
60
70
80
90
100
0
1 1000
V
IN
= 2.7V
V
IN
= 3.3V
V
IN
= 5.5V
STEP-UP REGULATOR OUTPUT VOLTAGE
vs. LOAD CURRENT (V
MAIN
= 9V)
MAX1997 toc02
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
10010
8.6
8.7
8.8
8.9
9.0
9.1
8.5
1 1000
V
IN
= 2.7V
V
IN
= 3.3V
V
IN
= 5.5V
STEP-UP REGULATOR EFFICIENCY
vs. LOAD CURRENT (V
MAIN
= 13V)
MAX1997 toc03
LOAD CURRENT (mA)
EFFICIENCY (%)
10010
10
20
30
40
50
60
70
80
90
100
0
1 1000
V
IN
= 2.7V
V
IN
= 3.3V
V
IN
= 5.5V
STEP-UP REGULATOR EFFICIENCY
vs. LOAD CURRENT
MAX1997 toc04
LOAD CURRENT (mA)
EFFICIENCY (%)
10010
10
20
30
40
50
60
70
80
90
100
0
1 1000
V
IN
= 5.5V
V
IN
= 3.3V
V
IN
= 2.7V
750kHz OPERATION
L = 4.7µH COILCRAFT LPO25061B-472
C
OUT
= 3 x 4.7µF/10V X7R CERAMIC
STEP-UP REGULATOR
SWITCHING FREQUENCY vs. INPUT VOLTAGE
MAX1997 toc05
INPUT VOLTAGE (V)
FREQUENCY (kHz)
5.04.54.03.53.0
500
700
900
1100
1300
1500
1700
300
2.5 5.5
V
MAIN
= 9V
I
MAIN
= 200mA
FREQUENCY = V
IN
FREQUENCY = OPEN
FREQUENCY = 0
STEP-UP REGULATOR NORMAL OPERATION
(200mA LOAD)
MAX1997 toc06
1µs/div
B
A
C
1A
10V
0
8.98V
9V
9.02V
0
5V
A: V
LX
, 5V/div
B: V
MAIN
= 9V, 20mV/div, AC-COUPLED
C: INDUCTOR CURRENT, 1A/div
STEP-UP REGULATOR LOAD TRANSIENT RESPONSE
(WITHOUT LAG COMPENSATION, FIGURE 1)
MAX1997 toc07
10µs/div
B
A
C
0.5A
200mA
0
1A
8.95V
9V
0
A: I
MAIN
= 0 TO 200mA, 200mA/div
B: V
MAIN
= 9V, 50mV/div, AC-COUPLED
C: INDUCTOR CURRENT, 500mA/div