To Supply

VOUT

GND

LM2776

To GND Plane

To Load

C1-

C1+

EN

VIN

C1

Input Voltage (V)

2.7

3.1

3.5

3.9

4.3

4.7

5.1

5.4

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

D005

15

LM2776

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SNVSA56A – MAY 2015 – REVISED FEBRUARY 2016

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8.2.3 Application Curve

Figure 20. Output Impedance vs Input Voltage

9 Power Supply Recommendations

The LM2776 is designed to operate from an input voltage supply range from 2.7 V to 5.5 V. This input supply

must be well regulated and capable to supply the required input current. If the input supply is located far from the

LM2776 additional bulk capacitance may be required in addition to the ceramic bypass capacitors.

10 Layout

10.1 Layout Guidelines

The high switching frequency and large switching currents of the LM2776 make the choice of layout important.

Use the following steps as a reference to ensure the device is stable and maintains proper LED current

regulation across its intended operating voltage and current range:

•

the input capacitor through short, wide traces to both the VIN and GND pins reduces the inductive voltage

spikes that occur during switching which can corrupt the VIN line.

•

circuitry.

•

Place C1 on the top layer (same layer as the LM2776) and as close to the device as possible. Connect the

flying capacitor through short, wide traces to both the C1+ and C1– pins.

10.2 Layout Example

Figure 21. LM2776 Layout Example