Owner manual

MAX8728
Low-Cost, Multiple-Output
Power Supply for LCD Monitors/TVs
6 _______________________________________________________________________________________
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 1150Switching 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 mΩ
LX1-to-GND1 Switch
On-Resistance
840Ω
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