Rainbow Electronics MAX8728 - Manual (Page 6)

MAX8728
Low-Cost, Multiple-Output
Power Supply for LCD Monitors/TVs
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ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V IN = V INL = V SUPP = 12V, V OUT1 = +3.3V, V SRC = 28V, GND1 = GND2 = GNDP = GND = 0, I REF = 0, T A =
-40°C to +85°C.) (Note 2)
PARAMETER CONDITIONS MIN TYP MAX UNITS
GENERAL
IN, INL Input Voltage Range For VL regulator operation 7.0 13.2 V
IN Standby Supply Current V IN = 7V to 13.2V, EN = SHDN = GND 0.5 mA
FSEL = GND 1175 1800
FSEL = V CC 780 1150 Switching Frequency
FSEL = REF 400 610
kHz
VL REGULATOR
VL Output Voltage
7V < V INL < 13.2V, V FB1 = V FB2 = V FBP = 1.9V,
V FBN = 0.5V, I VL = 25mA
4.8 5.1 V
VL Undervoltage Lockout
Threshold
VL rising, 2.5% hysteresis 3.8 4.1 V
REFERENCE
REF Output Voltage No external load 1.97 2.02 V
REF Load Regulation 0 < I RFI < 50µA 10 mV
STEP-DOWN REGULATOR
OUT1 Voltage in Fixed Mode
V IN = 6.0V to 13.2V, EN = V CC ,
I LOAD = 0.5A (Note 1)
3.23 3.35 V
FB1 Regulation Voltage in
Adjustable Mode 20% to 35% duty cycle, EN = V CC ,
I OUT1 = 0.5A (Note 1)
1.97 2.03 V
FB1 Adjustable-Mode
Threshold Voltage
0.10 0.20 V
Output Voltage Adjust Range 2.0 3.6 V
Step-Down Regulator Fault Trip
Level
Adjustable mode, FB1 falling 1.536 1.664 V
LX1-to-IN Switch
On-Resistance
550 m Ω
LX1-to-GND1 Switch
On-Resistance
8 40 Ω
Positive Current Limit 2.3 3.1 A
Skip Mode I MAX Threshold EN = GND 0.45 0.75 A
Maximum Duty Cycle 70 85 %
STEP-UP REGULATOR
Output Voltage Range V IN 17 V
Maximum Duty Cycle 65 85 %
FB2 Regulation Voltage FB2 = COMP, C COMP = 1nF 1.97 2.02 V
LX2 Current Limit V FB2 = 1.8V, duty cycle is 25% 1.2 1.8 A
LX2 On-Resistance 1 Ω