Datasheet

MAX1953/MAX1954/MAX1957
Low-Cost, High-Frequency, Current-Mode PWM
Buck Controller
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PARAMETER CONDITIONS MIN TYP MAX UNITS
ILIM Input Impedance MAX1953 only 50 125 200 kΩ
V
PGND
- V
LX
, ILIM = GND (MAX1953 only) 85 105 125
V
PGND
- V
LX
, ILIM = open (MAX1953 only) 190 210 235
V
PGND
- V
LX
, ILIM = IN (MAX1953 only) 290 320 350
Current-Limit Threshold
V
PGND
– V
LX
(MAX1954/MAX1957 only) 190 210 235
mV
OSCILLATOR
MAX1953 0.8 1 1.2 MHz
Switching Frequency
MAX1954/MAX1957 240 300 360 kHz
Maximum Duty Cycle Measured at DH 86 89 96 %
MAX1953, measured at DH 15 18
Minimum Duty Cycle
MAX1954/MAX1957, measured at DH 4.5 5.5
%
SOFT-START
MAX1953 4
Soft-Start Period
MAX1954/MAX1957 3.4
ms
FET DRIVERS
DH On-Resistance, High State 2 3 Ω
DH On-Resistance, Low State 1.5 3 Ω
DL On-Resistance, High State 2 3 Ω
DL On-Resistance, Low State 0.8 2 Ω
LX, BST Leakage Current
V
BST
= 10.5V, V
LX
= V
IN
= 5.5V,
MAX1953/MAX1957
20 µA
LX, BST, HSD Leakage Current
V
BST
= 18.7V, V
LX
= 13.2V, V
IN
= 5.5V
V
HSD
= 13.2V (MAX1954 only)
30 µA
THERMAL PROTECTION
Thermal Shutdown Rising temperature 160 °C
Thermal Shutdown Hysteresis 15 °C
SHUTDOWN CONTROL
COMP Logic Level Low 3V < V
IN
< 5.5V 0.25 V
COMP Logic Level High 3V < V
IN
< 5.5V 0.8 V
COMP Pullup Current 100 µA
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 5V, V
BST
- V
LX
= 5V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
Note 1: Specifications to -40°C are guaranteed by design and not production tested.
Note 2: HSD and IN are externally connected for applications where V
HSD
< 5.5V.