LTC1515 查看數據表（PDF） - Linear Technology
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LTC1515 Datasheet PDF : 8 Pages
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LTC1515 Series
PIN FUNCTIONS
C1+ (Pin 6): Charge Pump Flying Capacitor, Positive
Terminal.
VIN (Pin 7): Charge Pump Input Voltage. May be between
2V and 10V. VIN should be bypassed with a ≥ 10µF low
ESR capacitor as close as possible to the pin for best
performance.
W
W
SI PLIFIED BLOCK DIGRAM
VOUT (Pin 8): Regulated Output Voltage. Pin selectable to
either 3V/5V, 3.3V/5V or adjustable using an external
resistor divider (LTC1515). VOUT should be bypassed with
a ≥ 10µF low ESR capacitor as close as possible to the pin
for best performance.
VIN
SHDN
C1–
C1+
650kHz
OSCILLATOR
STEP-UP/STEP-DOWN
CHARGE PUMP
(LTC1515-X)
(LTC1515-X)
EN
VOUT
POR
RESET
EN
COUNTER
VOS
FB
(LTC1515)
1.232V
VREF
5/ 3
(LTC1515-X)
GND
LTC1515 • BD
APPLICATIONS INFORMATION
Regulator Operation
The regulator section of the LTC1515, LTC1515-3/5 and
LTC1515-3.3/5 consists of a charge pump, reference,
comparator and some logic. The divided down output
voltage is compared to the internal reference voltage.
When the divided output drops below the reference volt-
age, the charge pump is enabled, which boosts the output
back into regulation. Hysteresis in the comparator forces
the regulator to burst on and off and causes approximately
100mV of peak-to-peak ripple to appear at the output. By
enabling the charge pump only when needed, the parts
achieve high efficiencies with low output load currents.
Each part’s charge pump has a unique architecture that
allows the input voltage to be either stepped up or stepped
down to produce a regulated output. Internal circuitry
senses the VIN to VOUT differential voltage and controls the
charge pump operating mode. In addition, the effective
output impedance of the charge pump is internally
adjusted to prevent large inrush currents and allow for a
wide input voltage range. When the input voltage is lower
than the output voltage, the charge pump operates as a
step-up voltage doubler. When the input voltage is greater
than the output, the charge pump operates as a step-down
gated switch.
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