Datasheet

MAX1748/MAX8726
Triple-Output TFT-LCD
DC-DC Converters
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(Circuit of Figure 5, V
IN
= 3.3V, T
A
= +25°C, unless otherwise noted.)
8
10
18
20
12
16
14
22
24
58796101112
MAXIMUM POSITIVE CHARGE-PUMP OUTPUT
VOLTAGE vs. SUPPLY VOLTAGE
MAX1748/8726 toc10
V
SUPP
(V)
V
POS
(V)
I
POS
= 10mA
V
POS
= 22V
I
POS
= 1mA
I
POS
= 20mA
0.80
0.85
0.90
1.05
1.00
0.95
1.10
1.15
1.20
2.5 3.53.0 4.0 4.5 5.0 5.5
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
MAX1748/8726 toc11
INPUT VOLTAGE (V)
SWITCHING FREQUENCY (MHz)
MEASURED FROM THE
FALLING EDGE OF LX
V
MAIN
= 10V
I
MAIN
= 100mA
1.244
1.246
1.250
1.248
1.252
1.254
0201510 3025535404550
REFERENCE VOLTAGE
vs. REFERENCE LOAD CURRENT
MAX1748/8726 toc12
I
REF
(
μ
A)
V
REF
(V)
V
IN
= 3.3V
V
MAIN
10mV/div
V
NEG
10mV/div
V
POS
10mV/div
RIPPLE WAVEFORMS
MAX1748/8726 toc13
1μs/div
V
MAIN
= 10V, I
MAIN
= 200mA,
V
NEG
= -5V, I
NEG
= 10mA,
V
POS
= 15V, I
POS
= 10mA
I
MAIN
200mA/div
I
LX
500mA/div
V
MAIN
200mV/div
LOAD-TRANSIENT RESPONSE
MAX1748/8726 toc14
100μs/div
V
IN
= 3.3V, V
MAIN
= 10V,
R
MAIN
= 500Ω TO 50Ω (20mA TO 200mA)
I
MAIN
200mA/div
I
LX
500mA/div
V
MAIN
200mV/div
LOAD-TRANSIENT RESPONSE
WITHOUT INTEGRATOR
MAX1748/8726 toc15
100μs/div
V
IN
= 3.3V, V
MAIN
= 10V, INTG = REF,
R
MAIN
= 500Ω TO 50Ω (20mA TO 200mA)
-11
-9
-10
-7
-8
-4
-5
-6
-3
5867 9101112
MAXIMUM NEGATIVE CHARGE-PUMP
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
MAX1748/8726 toc07
V
SUPN
(V)
V
NEG
(V)
I
NEG
= 20mA
I
NEG
= 1mA
I
NEG
= 10mA
V
NEG
= -10mA
14.4
14.5
14.6
14.9
15.0
14.7
14.8
15.2
15.1
15.3
086102 4 12 14 16 18 20
POSITIVE CHARGE-PUMP OUTPUT
VOLTAGE vs. LOAD CURRENT
MAX1748/8726 toc08
I
POS
(mA)
V
POS
(V)
V
SUPN
= 12V
V
SUPN
= 8V
V
SUPN
= 10V
40
50
80
60
70
90
100
086102 4 12 14 16 18 20
POSITIVE CHARGE-PUMP EFFICIENCY
vs. LOAD CURRENT
MAX1748/8726 toc09
I
POS
(mA)
EFFICIENCY (%)
V
SUPP
= 12V
V
SUPP
= 8V
V
SUPP
= 10V