Rainbow Electronics MAX8758 - Manual (Page 7)

MAX8758
Step-Up Regulator with Switch Control and
Operational Amplifier for TFT LCD
_______________________________________________________________________________________ 7
STEP-UP REGULATOR PULSED LOAD
TRANSIENT RESPONSE
MAX8758 toc09
20µs/div
V MAIN
AC-COUPLED
200mV/div
L = 4.7µH
R COMP = 100kΩ
C COMP1 = 220pF
C COMP2 = 47pF
I MAIN
1A/div
I L
1AV/div
TIMER-DELAY LATCH RESPONSE
TO OVERLOAD
MAX8758 toc10
20ms/div
V MAIN
5V/div
LX
5V/div
I L
2A/div
0A
0V
0V
MAX8758 toc11
SUPB SUPPLY CURRENT
vs. SUPB VOLTAGE
V SUPB (V)
I SUPB
(mA)
4.5 6.0 7.5 9.0 10.5 12.0 13.5 15.0
0.10
0.15
0.20
0.25
0.30
NO LOAD
BUFFER CONFIGURATION
POS_ = V
SUPB / 2 MAX8758 toc12
SUPB SUPPLY CURRENT
vs. TEMPERATURE
TEMPERATURE (°C)
I SUPB
(mA)
-40 -10 20 50 70
0.10
0.15
0.20
0.25
0.30
NO LOAD
BUFFER CONFIGURATION
V
POSB = V SUPB / 2
V SUPB = 12V
V SUPB = 8V
V SUPB = 5V
OPERATIONAL AMPLIFIER FREQUENCY
RESPONSE FOR VARIOUS C LOAD
MAX8758 toc13
FREQUENCY (Hz)
MAGNITUDE (dB)
10k 1k
-40
-30
-20
-10
0
10
-50
100 100k
V SUP = 8.5V
A V = 1
R L = 10kΩ
1000pF
56pF
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX8758 toc14
FREQUENCY (Hz)
PSRR (dB)
100k 10k 1k 100 10
20
40
60
80
100
120
0
1 1M
V SUPB = 8.5V
OP-AMP RAIL-TO-RAIL INPUT/OUTPUT
MAX8758 toc15
100µs/div
V POSB
5V/div
V OUTB
5V/div
OP-AMP LOAD TRANSIENT RESPONSE
MAX8758 toc16
1µs/div
I OUTB
50mA/div
0
V OUTB
2V/div
Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
IN
= 3.3V, V
MAIN
= 8.5V, FREQ = SHDN = IN, T
A
= +25°C, unless otherwise noted.)