LT1947EMSE データシートの表示（PDF） - Linear Technology

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LT1947EMSE

Adjustable Output TFT-LCD Triple Switching Regulator

Linear Technology 

LT1947

PI FU CTIO S

FB1 (Pin 1): Feedback Pin for First Switcher. Connect

resistor divider tap here. Set AVDD according to:

AVDD = 1.26V(1 + R1/R2).

FB2 (Pin 2): Feedback Pin for Second Switcher. Connect

resistor divider 2 here and set VON using:

VON = 1.26V (1 + R3/R4) – 160mV.

CT (Pin 3): Timing Capacitor Pin. Connect a 10nF capacitor

from CT to ground to program a 2.3ms delay from FB1

reaching 1.26V to VON turning on.

SW1 (Pin 4): AVDD Switch Node. Connect L1 and D1 here

(see Figure 1). Minimize trace area at this pin to keep EMI

down.

GND (Pin 5): Ground. Connect directly to local ground

plane.

VIN (Pin 6): Input Supply Pin. Must be bypassed with a

ceramic capacitor close to the pin.

SW2 (Pin 7): VO2 Switch Node. Connect L2 and D2 here.

Minimize trace area at this pin to keep EMI down.

SHDN (Pin 8): Pull this pin low for shutdown mode. For

normal operation, tie to a voltage between 2.4V and 8V.

VO2 (Pin 9): SW2 Output. This node is also internally

connected to the emitter of Q3 (see Block Diagram), the

high side switch between VO2 and VON.

VON (Pin 10): This is the delayed output for second

Switcher. VON reaches its programmed voltage after the

internal timer times out.

Exposed Pad (Pin 11): Ground (MSE package only). The

exposed pad must be soldered to the PCB and electrically

connected to ground.

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