AIC1578 Datasheet, PDF (4/7 Pages) Analog Intergrations Corporation – High-Efficiency, Step-Down DC/DC Converter

BLOCK DIAGRAM
VIN ¹
DUTY ²
SHDN ³
FB ⁴
PFM
OSC
Current Limit Comparator
70mV
+
-
VIN
LATCH
8 _CS+
7 _CS-
-
+ Error
Comparator
1.22V
Ref erence
Voltage
Output
Driver
6
DRI
5 _GND
AIC1578
PIN DESCRIPTIONS
PIN 1: VIN - 4V to 20V input supply voltage.
PIN 2: DUTY - Duty cycle adjustment pin. To be
tied to the VIN pin directly or
through a resistor R_DUTY to adjust
oscillator duty cycle. R_DUTY must
be above 1MΩ if V_IN=20V.
See TYPICAL PERFORMANCE
CHARACTERISTICS.
PIN 3:
SHDN- Logical input to shutdown the
chip:
VSHDN = High for normal
operation.
VSHDN = Low for shutdown.
This pin should not be floating or
forced to greater than 15V. In
shutdown mode DRI pins is at
high level.
PIN 4: FB
- Feedback comparator input, to
compare the feedback voltage
with the internal reference
voltage. Connecting a resistor R1
to converter output node and a
resistor R2 to ground yields the
output voltage:
V_OUT=1.22 ×(R1+R2)/ R2
PIN 5: GND - Power ground.
PIN 6: DRI
- Push-pull driver output to drive
an external P-channel MOSFET
or PNP transistor. When driving
a PNP bipolar transistor, a base
resistor and a capacitor to the
base of PNP are recommended.
PIN 7: CS- - Current sense comparator
inverting input, not to exceed V_IN
voltage.
PIN 8: CS+ - Current sense comparator non-
inverting input, not to exceed V_IN
voltage.
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