Typical Application Circuit
PWM CONTROL 3A STEP-DOWN CONVERTER
Note: VOUT = VFB x (1+RA/RB)
The AP1510 consists of DC/DC converters that employ a
pulse-width modulation (PWM) system.
In converters of the AP1510, the pulse width varies in a range
from 0 to 100%, according to the load current. The ripple voltage
produced by the switching can easily be removed through a filter
because the switching frequency remains constant. Therefore,
these converters provide a low-ripple power over broad ranges of
input voltage and load current.
Under Voltage Lockout
The under voltage lockout circuit of the AP1510 assures that the
high-side MOSFET driver outputs remain in the off state
whenever the supply voltage drops below 3.3V. Normal operation
resumes once VCC rises above 3.5V.
RDS(ON) Current Limiting
The current limit threshold is setting by the external resistor
connecting from VCC supply to OCSET. The internal 100uA sink
current crossing the resistor sets the voltage at pin of OCSET.
When the PWM voltage is less than the voltage at OCSET, an
over-current condition is triggered.
ILOAD × RDS(ON) = IOCSET × ROCSET
See above formula for setting the current limit value.
AP1510 Rev. 1
4 of 8
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