MAX1881 Просмотр технического описания (PDF) - Maxim Integrated
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MAX1881 Datasheet PDF : 38 Pages
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Quad-Output TFT LCD DC-DC
Converters with Buffer
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = +3.3V, SHDN = IN, VMAIN = VSUPP = VSUPN = VSUPB = VSUPL = 8V, BUF- = BUFOUT,
BUF+ = FLTSET = TGND = PGND = GND, TA = +25°C.)
RIPPLE VOLTAGE WAVEFORMS
MAX1778 toc16
8V
A
-5V
B
20V
C
1µs/div
A. VMAIN = 8V, IMAIN = 200mA, 10mV/div
B. VNEG = -5V, INEG = 10mA, 20mV/div
C. VPOS = 20V, IPOS = 5mA, 20mV/div
STEP-UP CONVERTER
SOFT-START (LIGHT LOAD)
MAX1778 toc17
2V
A
0
8V
6V
B
4V
0.5A
C
0
1ms/div
A. VSHDN = O TO 2V, 2V/div
B. VMAIN = 8V, 2V/div
C. INDUCTOR CURRENT, 500mA/div
RLOAD = 400Ω
STEP-UP CONVERTER
SOFT-START (HEAVY LOAD)
MAX1778 toc18
2V
A
0
8V
6V
B
4V
1.0A
C
0.5A
0
1ms/div
A. VSHDN = O TO 2V, 2V/div
B. VMAIN = 8V, 2V/div
C. INDUCTOR CURRENT, 500mA/div
RLOAD = 20Ω
POWER-UP SEQUENCE
MAX1778 toc19
POWER-UP SEQUENCE
(CIRCUIT OF FIG.10)
4V
MAX1778 toc20
2V
2V
A
A
0
0
5V
20V
B
B
0
10V
C
20V
C
0
10V
D
0
D
0
-5V
E
-10V
2ms/div
1ms/div
A. VSHDN = O TO 2V, 2V/div
B. RDY, 5V/div
C. POSITIVE CHARGE PUMP = VPOS = 20V, RLOAD = 4kΩ, 10V/div
D. STEP-UP CONVERTER: VMAIN = 8V, RLOAD = 40Ω, 10V/div
E. NEGATIVE CHARGE PUMP: VNEG = -5V, RLOAD = 500Ω, 10V/div
A. RDY, 2V/div
B. POSITIVE CHARGE PUMP, VPOS(SYS) = 20V, 10V/div
C. STEP-UP CONVERTER: VMAIN(SYS) = 8V, 10V/div
D. NEGATIVE CHARGE PUMP, VNEG = -5V, -5V/div
POWER-UP INTO SHORT-CIRCUIT
(CIRCUIT OF FIG. 10)
MAX1778 toc21
4V
2V
A
0
5V
0
B
10V
5V
C
0
100µs/div
A. RDY, 2V/div
B. GATE OF N-CH MOSFET, 5V/div
C. STEP-UP CONVERTER, VMAIN(START) = 8V, 5V/div
VMAIN(SYS) = GND
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