Datasheet

MAX1856
Wide Input Range, Synchronizable,
PWM SLIC Power Supply
4 _______________________________________________________________________________________
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
R
OSC
= 100kΩ ±1% 86 94
R
OSC
= 200kΩ ±1% 87 93Maximum Duty Cycle D
R
OSC
= 500kΩ ±1% 86 94
%
Minimum SYNC Input Signal
Duty Cycle
45 %
Minimum SYNC Input
Low Pulse Width
200 ns
SYNC Input Frequency Range f
SYNC
100 500 kHz
SYNC/SHDN Input High Voltage V
IH
2.0 V
SYNC/SHDN Input Low Voltage V
IL
0.45 V
V
SYNC/SHDN
= 5V 3.0
SYNC/SHDN Input Current
V
SYNC/SHDN
= 28V 10
µA
EXT On-Resistance R
ON
(
EXT
)
EXT high or low 5 Ω
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= SYNC/SHDN, V
CC
= 5V, V
LDO
= 5V, R
OSC
= 200kΩ, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 3)
Note 1: This is the V
CC
current consumed when active, but not switching, so the gate-drive current is not included.
Note 2: The reference output voltage (V
REF
) is measured with respect to FB. The difference between REF and FB is guaranteed to
be within these limits to ensure output voltage accuracy.
Note 3: Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, V
CC
= V
SYNC/SHDN
= 12V, V
OUT1
= -24V, V
OUT2
= -72V, R
OSC
= 200kΩ, unless otherwise noted.)
-24.5
-24.0
-23.0
-23.5
-22.5
-22.0
0 200100 300 400 500 600 700
-24V OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1856 toc01
I
OUT1
(mA)
V
OUT1
(V)
V
IN
= 5V
V
IN
= 12V
V
IN
= 24V
V
OUT1
= -24V
V
OUT2
= -72V
I
OUT2
= 5mA
-74.5
-74.0
-73.0
-73.5
-72.5
-72.0
0 200100 300 400 500 600 700
-72V CROSS-REGULATION VOLTAGE
vs. LOAD CURRENT
MAX1856 toc02
I
OUT1
(mA)
V
OUT2
(V)
V
IN
= 5V
V
IN
= 24V
V
OUT1
= -24V
V
OUT2
= -72V
I
OUT2
= 5mA
V
IN
= 12V
50
60
70
90
80
100
0 100 200 300 400 500 600 700
EFFICIENCY vs. LOAD CURRENT
(-24V OUTPUT)
MAX1856 toc03
I
OUT1
(mA)
EFFICIENCY (%)
V
OUT1
= -24V
V
OUT2
= -72V
I
OUT2
= 5mA
V
IN
= 5V
V
IN
= 24V
V
IN
= 12V