MAX750A Ver la hoja de datos (PDF) - Maxim Integrated
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MAX750A Datasheet PDF : 16 Pages
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Adjustable, Step-Down,
Current-Mode PWM Regulators
VIN
C5
330pF
R1
510K
SHDN
OVERCURRENT COMPARATOR
BIAS
GEN
SLOPE COMPENSATION
MAX750A
MAX758A
RAMP
Σ
GEN
RSENSE
R2
CC
R3
1.23V
BANDGAP
ERROR
AMP
F/F
R
Q
S
PWM
COMPARATOR
CURRENT
SENSE AMP
C6
0.01µF
C1
0.1µF
REF
1M
±35%
SS
SS CLAMP
OSC
UNDERVOLTAGE
LOCKOUT
V+
C2
C3*
1µF
LX
L1
D1
1N5817
VOUT
C4*
VUVLO
GND
* SEE TABLE 3 FOR COMPONENT VALUES AND SUPPLIERS.
Figure 1. Detailed Block Diagram with External Components
Overcurrent Limiting
The overcurrent comparator triggers when the load cur-
rent exceeds approximately 1.5A. On each clock
cycle, the output FET turns on and attempts to deliver
current until cycle-by-cycle or overcurrent limits are
exceeded. Note that the soft-start capacitor must be
greater than 0.01µF for overcurrent protection to func-
tion properly. A typical value is 0.1µF. A soft-start
cycle is initiated when the overcurrent comparator is
triggered.
Undervoltage Lockout
The undervoltage lockout feature monitors the supply
voltage at V+ and allows operation to start when V+
rises above 3.75V. When V+ falls, operation continues
until the supply voltage falls below 3.50V. When an
undervoltage condition is detected, control logic turns
off the output power FET and discharges the soft-start
capacitor to ground. This prevents partial turn-on of
the power MOSFET and avoids excessive power dissi-
pation. The control logic holds the output power FET
off until the supply voltage rises above approximately
3.75V, at which time a soft-start cycle begins.
Shutdown Mode
The MAX750A/MAX758A are shut down by keeping
SHDN at ground. In shutdown mode, the output power
FET is held off and the output drops to 0V. The internal
reference also turns off, which causes the soft-start
capacitor to discharge. The 6µA typical standby cur-
rent includes external-component leakage currents. As
temperature increases past +85°C, the external capaci-
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