User Manual

MAX746
High-Efficiency, PWM, Step-Down,
N-Channel DC-DC Controller
_______________________________________________________________________________________ 3
Note 1: The soft-start fault current is the current sink capability of SS when V
REF
< 1V or when the device is in shutdown.
Note 2: I
SUPP
is the supply current drawn by V+, which includes the current drawn by the charge pump. The charge pump
doubles the current drawn by HIGH from the V+ input, so I
SUPP
= I
V+
+ 2I
HIGH
.
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 10V, I
LOAD
= 0A, I
REF
= 0µA, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
SHDN Input Leakage Current
SYMBOL MIN TYP MAX UNITS
LBO Output Voltage Low V
OL
nA
0.4 V
LBI Threshold Voltage
1.96 2.00 2.04
V
Compensation Pin Impedance 24
kΩ
EXT Source Current 270 mA
LBI Input Leakage Current nA
LBO Output Leakage Current 1
µA
SHDN Input Voltage Low V
IL
0.4 V
SHDN Input Voltage High V
IH
2.0 V
EXT Output Low
EXT Output High V
HIGH
- 0.1 V
0.25 V
EXT Sink Current 160 mA
MAX746E/M
CONDITIONS
SHDN = 10V
I
SINK
= 0.5mA
LBI falling
V
HIGH
= 15V, V
EXT
= 2.5V
LBI = 2.5V
V+ = 15V, LBO = 15V, LBI = 2.5V
V
HIGH
forced to 15V, I
EXT
= -1mA
V
HIGH
forced to 15V, I
EXT
= 1mA
V
HIGH
= 15V, V
EXT
= 12.5V
MAX746C 1.97 2.00 2.03
100
0.1 100
Charge-Pump Output Voltage
Maximum Duty Cycle 91 96 %
V
HIGH
V+ + 4 V+ + 5 V+ + 6 V
V
LIMIT
125 150 175 mV
V+ = 6V
I
HIGH
= 0mA to 10mA
V+ – CS
Current-Sense Amplifier
Current-Limit Threshold