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 <V
IN
< 13.2V, EN = V
CC
0.1
%/V
LX1-to-IN Switch
On-Resistance
200
300
m
Ω
LX1-to-GND1 Switch
On-Resistance
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