Datasheet

MAX1970/MAX1971/MAX1972
turns off and the internal low-side n-channel MOSFET
turns on. Now the inductor releases the stored energy
as its current ramps down while still providing current to
the output. The output capacitor stores charge when
the inductor current exceeds the load current and dis-
charges when the inductor current is lower, smoothing
the voltage across the load. Under overload conditions,
when the inductor current exceeds the current limit (see
the Current Limit section), the high-side MOSFET is not
turned on at the rising edge of the clock and the low-
side MOSFET remains on to let the inductor current
ramp down.
Current Sense
The current-sense circuit amplifies the current-sense
voltage generated by the high-side MOSFET’s on-resis-
tance and the inductor current (R
DS(ON)

I
INDUCTOR
).
This amplified current-sense signal and the internal
slope compensation signal are summed together into
Dual, 180° Out-of-Phase, 1.4MHz, 750mA Step-
Down Regulator with POR and RSI/PFO
12 ______________________________________________________________________________________
Figure 1. Functional Diagram
FB
SELECT
PWM CONTROL
LX1
PGND
RSI
PFO
POR
MAX1970/MAX1972 ONLY
MAX1971 ONLY
CLAMP
ERROR SIGNAL
REGULATOR 1
REGULATOR 2
FB1
IN
FBSEL1
COMP1
REF
EN
COMP2
FB2
FBSEL2
GND
SLOPE COMP
CURRENT SENSE
SOFT-START
THERMAL SHUTDOWN
VOK
REFERENCE
VOLTAGE
1.2V
÷2(MAX1970/
MAX1972)/
÷4(MAX1971)
2.8MHz
OSCILLATOR
POR
PFO
V
CC
MAX1970
MAX1971
MAX1972