34704 datasheet(17/54 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34704

FUNCTIONAL DESCRIPTION

FUNCTIONAL PIN DESCRIPTION

REG5 BOOST STAGE BOOTSTRAP CAPACITOR

INPUT PIN (BT5U)

Connect a 1.0

μF capacitor between this pin and SW5U

pin to enhance the gate of the Switch Power MOSFET.

REG4 BUCK STAGE BOOTSTRAP CAPACITOR

INPUT PIN (BT4D)

Connect a 0.01

μF capacitor between this pin and SW4D

pin to enhance the gate of the Switch Power MOSFET.

REG4 POWER SUPPLY INPUT VOLTAGE (PVIN4)

This is the connection to the drain of the high side switch

FET. Input decoupling /filtering is required for proper REG4

operation.

REG4 BUCK STAGE SWITCHING NODE (SW4D)

The inductor is connected between this pin and the SW4U

pin.

REG4 REGULATED OUTPUT VOLTAGE PIN

(VOUT4)

Connect this pin to the load and to the output filter as close

to the pin as possible.

REG4 BOOST STAGE SWITCHING NODE (SW4U)

The inductor is connected between this pin and the SW4D

pin.

REG4 BOOST STAGE BOOTSTRAP CAPACITOR

INPUT PIN (BT4U)

Connect a 0.01

μF capacitor between this pin and SW4U

pin to enhance the gate of the Switch Power MOSFET.

REG4 VOLTAGE FEEDBACK INPUT FOR

VOLTAGE REGULATION/PROGRAMMING (FB4)

Connect the feedback resistor divider to this pin.

REG4 COMPENSATION NETWORK CONNECTION

(COMP4)

REG4 compensation network connection.

REG3 BOOTSTRAP CAPACITOR INPUT PIN (BT3)

Connect a 0.01

μF capacitor between this pin and SW3 pin

to enhance the gate of the Switch Power MOSFET.

REG3 POWER SUPPLY INPUT VOLTAGE (PVIN3)

This is the connection to the drain of the high side switch

FET. Input decoupling /filtering is required for proper REG3

operation.

REG3 SWITCHING NODE (SW3)

The inductor is connected between this pin and the

regulated REG3 output.

REG3 OUTPUT VOLTAGE RETURN PIN (VOUT3)

This is the discharge path of REG3 output voltage.

REG3 VOLTAGE FEEDBACK INPUT FOR

VOLTAGE REGULATION/PROGRAMMING (FB3)

Connect the feedback resistor divider to this pin.

SOFT START TIME (SS)

The soft start time for all regulators can be adjusted by

connecting this pin to an external resistor divider between

VDDI and AGND pins.

OSCILLATOR FREQUENCY (FREQ)

The oscillator frequency can be adjusted by connecting

this pin to an external resistor divider between VDDI and

AGND pins. This pin sets FSW1 value.

REG8 VOLTAGE FEEDBACK INPUT FOR

VOLTAGE REGULATION/PROGRAMMING (FB8)

Connect the feedback resistor divider to this pin, when

voltage mode control is used. When current mode control is

used, connect this pin between the LED string and an ISET

resistor to GND to force the operating current. Refer to

Figure 10 and Figure 11. Exclude the components not used.

REG8 BOOTSTRAP CAPACITOR INPUT PIN (BT8)

Connect a 0.01

μF capacitor between this pin and SW8 pin

to enhance the gate of the Synchronous Power MOSFET.

REG8 REGULATED OUTPUT VOLTAGE PIN

(VOUT8)

Connect this pin directly to the load directly and to the

output filter as close to the pin as possible.

REG8 SWITCHING NODE (SW8)

The inductor is connected between this pin and VIN pin.

REG1 SWITCHING NODE (SW1)

The inductor is connected between this pin and VIN pin.

REG1 REGULATED OUTPUT VOLTAGE BEFORE

THE CUT-OFF SWITCH (VG)

REG1 regulated output voltage before the cutoff switch.

This supplies the internal circuits and the gate drive.

34704 Datasheet(PDF) 17 Page - Freescale Semiconductor, Inc

34704 Datasheet(HTML) 17 Page - Freescale Semiconductor, Inc

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