34716 datasheet(12/25 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34716

FUNCTIONAL DESCRIPTION

FUNCTIONAL PIN DESCRIPTION

ERROR AMPLIFIER INVERTING INPUT (INV1, INV2)

Buck converter error amplifier inverting input. Connect the

VDDQ voltage (channel 1) to INV1 pin through a resistor

divider and connect the VTT voltage (channel 2) directly to

INV2 pin.

OUTPUT VOLTAGE DISCHARGE PATH (VOUT1,

VOUT2)

Buck converters output voltage are connected to these

pins. It only serves as the output discharge path once the SD

signal is asserted.

INTERNAL SUPPLY VOLTAGE OUTPUT (VDDI)

This is the output of the internal bias voltage regulator.

Connect a 1.0 µF, 6 V low ESR ceramic filter capacitor

between this pin and the GND pin. Filtering any spikes on this

output is essential to the internal circuitry stable operation.

SIGNAL GROUND (GND)

Analog ground of the IC. Internal analog signals are

referenced to this pin voltage.

INPUT SUPPLY VOLTAGE (VIN)

IC power supply input voltage. Input filtering is required for

the device to operate properly.

POWER GOOD OUTPUT SIGNAL (PG)

This is an active low open drain output that is used to

report the status of the device to a host. This output activates

after a successful power up sequence and stays active as

long as the device is in normal operation and is not

experiencing any faults. This output activates after a 10 ms

delay and must be pulled up by an external resistor to a

supply voltage like VIN.

STANDBY INPUT (STBY)

If this pin is tied to the GND pin, the device will be in

Standby Mode. If left unconnected or tied to the VIN pin, the

device will be in Normal Mode. The pin has an internal pull up

of 1.5 M

Ω. This input accepts the S3 (Suspend-To-RAM)

control signal.

SHUTDOWN INPUT (SD)

If this pin is tied to the GND pin, the device will be in

Shutdown Mode. If left unconnected or tied to the VIN pin, the

device will be in Normal Mode. The pin has an internal pull up

of 1.5 M

Ω. This input accepts the S5 (Suspend-To-Disk)

control signal.

REFERENCE VOLTAGE OUTPUT (VREFOUT)

This is a buffered reference voltage output that is equal to

1/2 VREFIN. It has a 10.0 mA current drive capability. This

output is used as the VREF voltage rail and should be filtered

against any noise. Connect a 0.1 µF, 6 V low ESR ceramic

filter capacitor between this pin and the GND pin and

between this pin and VDDQ rail. VREFOUT is also used as the

reference voltage for the buck converter error amplifier.

REFERENCE VOLTAGE INPUT (VREFIN)

The output of channel two will track 1/2 the voltage applied

at this pin.

FREQUENCY ADJUSTMENT INPUT (FREQ)

The buck converters switching frequency can be adjusted

by connecting this pin to an external resistor divider between

VDDI and GND pins. The default switching frequency (FREQ

pin connected to ground, GND) is set at 1.0 MHz.

CHANNEL 1 SOFT START ADJUSTMENT INPUT

(ILIM1)

Channel one Soft Start can be adjusted by applying a

voltage between 1.25V and VDDI.

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