LP3936

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SNVS259D – NOVEMBER 2003 – REVISED MAY 2013

Magnetic Boost DC/DC Converter Electrical Characteristics

Symbol

Parameter

Conditions

Min

Typ

Max

Units

Load Current

3.0V

0

250

mA

Output Voltage Accuracy (FB Pin)

1 mA

3.0V

−5

+5

%

Output Voltage (FB Pin)

1 mA

4.55

V

1 mA

V

Switch ON Resistance

0.4

0.5

Ω

PWM Mode Switching Frequency

RT = 82 k

Ω

1

MHz

Frequency Accuracy

RT = 82 k

Ω

−6

±3

+6

%

−10

+10

Startup Time

25

ms

OUT Pin Current Limit

600

750

1050

mA

400

1200

PFM/PWM Mode

User can change the Boost converters mode between PWM (Pulse Width Modulation) and PFM (Pulse

Frequency Modulation). The startup is done on PFM mode and then the device runs on PWM mode (as a

default). User can set PFM mode by turning “pfm_mode” register bit HIGH. PFM is recommended to use with

light loads and PWM with high loads.

Boost Standby Mode

User can set boost converter to STANDBY mode by writing register bit EN_BOOST low. This mode can be

useful when driving LEDs directly from battery voltage. This may be possible if LED forward voltage is low,

battery voltage is high and LED current is low.

When EN_BOOST is written high, the converter starts for 10 ms in PFM mode and then goes to PWM mode if

PWM mode has been selected (default). During Boost Start-up all LEDs are turned off to reduce the load.

Unused Boost Converter

If the boost converter is not used, it should be disabled by writing bit en_boost low. OUT pin should be

connected to GND and FB pin to the LED supply voltage.

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