LTC3251_15 Datasheet, PDF (6/16 Pages) Linear Technology – 500mA High Efficiency, Low Noise, Inductorless Step-Down DC/DC Converter

LTC3251/
LTC3251-1.2/LTC3251-1.5
PI FU CTIO S
MD0 (Pin 1)/MD1 (Pin 9): Switching Mode Input Pins. The
Mode input pins are used to set the operating mode of the
LTC3251. The modes of operation are:
MD1
MD0
OPERATING MODE
0
0
Shutdown
0
1
Spread Spectrum with Burst
1
0
Continuous Spread Spectrum
1
1
Super Burst
MD0 and MD1 are high impedance CMOS inputs and must
not be allowed to float.
V_IN (Pin 2): Input Supply Voltage. Operating V_IN may be
between 2.7V and 5.5V. Bypass V_IN with a ≥ 1µF low ESR
ceramic capacitor to GND (C_OUT).
C1⁺ (Pin 3): Flying Capacitor 1 Positive Terminal (C1).
C1^– (Pin 4): Flying Capacitor 1 Negative Terminal (C1).
GND (Pin 5, 11): Ground. Connect to a ground plane for
best performance.
C2^– (Pin 6): Flying Capacitor 2 Negative Terminal (C2).
V_OUT (Pin 7): Regulated Output Voltage. V_OUT is discon-
nected from V_IN during shutdown. Bypass V_OUT with a
low ESR ceramic capacitor to GND (C_IN). See V_OUT
Capacitor Selection for capacitor size requirements.
C2⁺ (Pin 8): Flying Capacitor 2 Positive Terminal (C2).
FB (Pin 10) (LTC3251): Feedback Input Pin. An output
divider should be connected from V_OUT to FB to program
the output voltage.
MODE (Pin 10) (LTC3251-1.2/LTC3251-1.5): Spread
Spectrum Operation Mode Pin. A low voltage on MODE
enables spread spectrum operation. When MODE is high
spread spectrum operation is disabled and switching
occurs at the maximum operating frequency.
6
32511215fb