34844 datasheet(13/37 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34844

FUNCTIONAL DESCRIPTION

FUNCTIONAL PIN DESCRIPTION

A0/SEN

Address select, device select pin, or Hardware Over

voltage Protection (OVP) Control.

CURRENT SET (ISET)

Each LED string can drive up to 50mA. The maximum

current can be set by using a resistor from this pin to GND.

POSITIVE CURRENT SCALING (PIN)

Positive current scaling factor for the external analog

current control. Applying 0V to this pin, scales the current to

0%, and in the same way, applying 2.048V(Vset), the scale

factor is 100%. By applying a voltage higher than 2.2V, the

scaling factor is disabled, and the internal pull-ups are

activated.

If PIN pin and NIN pin are used at the same time then by

applying 0V to the PIN pin and 2.048V to NIN pin, scales the

current to 0%, and in the same way, applying 2.048V to the

PIN pin and 0V to NIN pin, scales the current to 100%. By

applying a voltage higher than 2.2V, the scaling factor is

disabled and the internal pull-ups are activated in both pins.

NEGATIVE CURRENT SCALING (NIN)

Negative current scaling factor for the external analog

current control. Setting 0V to this pin scales the current to

100%, in the same way, setting 2.048V (Vset) the scale factor

is 0%. By applying a voltage higher than 2.2V, the scaling

factor is disabled and the internal pull-ups are activated.

If PIN pin and NIN pin are used at the same time then by

applying 0V to the PIN pin and 2.048V to NIN pin, scales the

current to 0%, and in the same way, applying 2.048V to the

PIN pin and 0V to NIN pin, scales the current to 100%. By

applying a voltage higher than 2.2V, the scaling factor is

disabled and the internal pull-ups are activated in both pins.

GROUND (GND)

Ground Reference for all internal circuits other than the

Boost FET.

The Exposed Pad (EP) should be used for thermal heat

dissipation.

I0-I9

Current LED driver, each line has the capability of driving

up to 50mA.

FAULT DETECTION PIN (FAIL)

When a fault situation is detected, this pin goes into high

impedance.

BOOST SLOPE COMPENSATION SETTING

RESISTOR (SLOPE)

Use an external resistor of about 68k

Ω to configure the

Boost compensation slope.

POWER GROUND TERMINALS (PGNDA, PGNDB)

Ground terminal for the internal Boost FET.

OUTPUT VOLTAGE SENSE TERMINAL (VOUT)

Input terminal to monitor the output voltage. It also

supplies the input voltage for the internal regulator 2 (VDC2).

SWITCHING NODE TERMINALS (SWA, SWB)

Switching node of boost converter.

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