AIC1553CVTR Ver la hoja de datos (PDF) - Analog Intergrations
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AIC1553CVTR Datasheet PDF : 9 Pages
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AIC1553
PIN DESCRIPTIONS
PIN 1: SW
- Switch Node. The Switch node
connects to the inductor. This
pin swings from VIN to a
Schottky diode (external)
voltage drop below ground. The
cathode of the Schottky diode
must be closely connected to
this pin.
PIN 2: GND
PIN 3: VFB
- Ground Pin. Connect to the (-)
terminal of COUT, the Schottky
diode and (-) terminal of CIN.
- Output Feedback Pin. Receives
the feedback voltage from the
PIN 4: SD
PIN 5: VIN
external resistive divider across
the output. Nominal voltage for
this pin is 0.75V.
- Shutdown Pin. Voltage at 1.6V
or higher may enable the device.
Connect this pin to Ground for
shutdown.
- Main Power Supply. Main supply
pin and the (+) Input to the
Current Comparator. Must be
closely decoupled to ground.
APPLICATION INFORMATION
Overview
AIC1553 is a step-down DC-DC converter using
PWM current mode architecture. The 2.5V to
5.5V input voltage range ideally suited for single
Li-ion or 3cell NiMH/NiCd batteries applications.
0.75V of feedback reference voltage allows low
output voltages down to 0.75V. Switching
frequency is set at 500kHz, allowing the use of
tiny, small capacitors and inductor. Under
morning load current AIC1553 operates in PWM
mode with a fixed switching frequency of typical
500kHz. At light load current, the device
automatically enters the PFM mode operation,
the switching frequency is reducing to decrease
gate charge losses. At the same time, the
quiescent current is typically only 22µA to
achieve the high efficiency. In shutdown mode, it
draws less than 1µA, making it ideal for current
sensitive applications.
PWM Mode Operation
During PWM mode operation the converter uses
a fast response, current mode, controller circuitry
with input voltage feed forward. The fixed
switching frequency of typical 500kHz allowing
the use of tiny, small capacitors and inductor. The
current mode operation achieves excellent line
and load transient response. At the beginning of
each cycle, the high side P-MOSFET turns on.
The current flowed the inductor ramps up and is
sensed through an internal circuitry. The high
side P-MOSFET turns off until the sensed current
causes the PWM comparator to trip or the
inductor current reaches the peak switch current
threshold 0.7A. The inductor current flows
through the external Schottky diode to output
terminal. After the period, the switch turns on and
the next clock cycle starts again.
When the output terminal is short to ground, the
input peak current will be limit under the peak
switch current threshold 0.7A.
PFM Mode Operation
As the load is relatively light and the peak current
doesn’t reach the power save mode threshold,
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