MAX1534
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
_______________________________________________________________________________________ 5
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, ILIM = GND, PRESET = GND, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 4)
INPUTS AND OUTPUTS
SHDN Input Trip Level Rising trip level, 100mV hysteresis
0.96 1.04
V
Low 0.5 V
PRESET, ILIM Logic Levels
High 2.2 V
Note 1: The output voltage at light loads has a DC regulation level higher than the error comparator threshold by half the ripple volt-
age.
Note 2: The dropout voltage is defined as V
LDOIN
- V
OUT_
when V
LDOIN
= V
OUT_(NOM)
. Specification only applies when V
OUT_
≥
2.5V.
Note 3: OUT1, OUT2 DC set point, FB3 set point at the DC trip threshold of buck regulator.
Note 4: Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, V
IN
= +12V, PRESET = GND, T
A
= +25°C, unless otherwise noted.)
4.80
4.90
4.85
4.95
5.10
5.15
5.05
5.00
5.20
0 100 150 200 25050 300 350 400 450 500
BUCK OUTPUT VOLTAGE
vs. LOAD CURRENT, CIRCUIT 1
MAX1534 toc01
I
OUT3
(mA)
V
OUT3
(V)
V
IN
= 12V
V
IN
= 20V
V
IN
= 6V
(t
ON
LIMITED)
ILIM = IN
100
50
0.1 1 10 100 1000
BUCK EFFICIENCY
vs. LOAD CURRENT, CIRCUIT 1
60
MAX1534 toc02
I
OUT3
(mA)
EFFICIENCY (%)
70
80
90
85
75
65
55
95
ILIM = IN
V
IN
= 6V
V
IN
= 12V
V
IN
= 20V
0.1 1 10 100 1000
BUCK EFFICIENCY
vs. LOAD CURRENT, CIRCUIT 2
MAX1534 toc03
I
OUT3
(mA)
100
50
60
EFFICIENCY (%)
70
80
90
85
75
65
55
95
V
IN
= 12V
V
IN
= 20V
V
IN
= 7V
ILIM = GND
89
87
85
83
81
79
77
75
0.1 10 1001 1000
BUCK EFFICIENCY vs. LOAD CURRENT
CIRCUIT 1, V
IN
= 12V
MAX1534 toc04
I
OUT3
(mA)
EFFICIENCY (%)
L = 15µH
L = 10µH
L = 22µH
ILIM = IN
0
60
40
20
80
100
120
140
160
180
200
61410 18 22 26
SWITCHING FREQUENCY
vs. V
IN
, CIRCUIT 1, ILIM = IN
MAX1534 toc05
V
IN
(V)
FREQUENCY (kHz)
I
OUT3
= 500mA
I
OUT3
= 250mA
I
OUT3
= 100mA
I
OUT3
= 50mA
I
OUT3
= 10mA
