Electrical characteristics (continued) – Rainbow Electronics MAX8728 User Manual
Page 3
MAX8728
Low-Cost, Multiple-Output
Power Supply for LCD Monitors/TVs
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(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
= 0°C
to +85°C. Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
STEP-DOWN REGULATOR
OUT1 Voltage in Fixed Mode
V
IN
= 7.0V to 13.2V, EN = V
CC
,
I
LOAD
= 0.5A (Note 1)
3.25
3.30
3.35
V
FB1 Regulation Voltage in
Adjustable Modes
20% to 35% duty cycle, EN = V
CC
,
I
LOAD
= 0.5A (Note 1)
1.97
2.00
2.03
V
FB1 Adjustable Mode Threshold
Voltage
0.10
0.15
0.20
V
Output Voltage Adjust Range
2.0
3.6
V
Fixed mode, OUT1 falling
2.640
Step-Down Regulator Fault Trip
Level
Adjustable mode, FB1 falling
1.536
1.600
1.664
V
FB1 Input Leakage Current
V
FB1
= 2.1V
-100
+100
nA
Low-Frequency Operation
OUT1 Threshold
LX1 only
1.3
V
FSEL = GND
250
FSEL = V
CC
167
Low-Frequency Operation
Switching Frequency
LX1 only
FSEL = REF
83
kHz
DC Load Regulation
0 < I
OUT1
< 2A, EN = V
CC
0.5
%
DC Line Regulation
7V IN < 13.2V, EN = V CC 0.1 %/V LX1-to-IN Switch 200 300 m Ω LX1-to-GND1 Switch 10 22 40 Ω Positive Current Limit 2.5 2.8 3.1 A Skip Mode I MAX Threshold EN = GND 0.50 0.60 0.75 A Soft-Start Ramp Time 1.7 ms Maximum Duty Cycle 70 77 85 % STEP-UP REGULATOR Output Voltage Range V IN 17 V Maximum Duty Cycle 65 75 85 % Minimum On-Time 65 100 ns FB2 Regulation Voltage FB2 = COMP, C COMP = 1nF 1.98 2.00 2.02 V FB2 Fault Trip Level Falling edge 1.728 1.800 1.872 V FB2 Load Regulation 0 < I AVDD < full, transient only -1 % FB2 Line Regulation V IN = 10.8V to 13.2V 0.08 0.15 %/V FB2 Input Bias Current V FB2 = 2V -150 +150 nA FB2 Transconductance ΔI = ±2.5µA at COMP, FB2 = COMP 75 160 280 µS FB2 Voltage Gain FB2 to COMP 700 V/V LX2 Leakage Current V FB2 = 2.1V, V LX2 = 13V 4 40 µA LX2 Current Limit V FB2 = 1.8V, duty cycle is 25% 1.2 1.5 1.8 A
On-Resistance
On-Resistance