PC33814AE datasheet(20/50 Pages) FREESCALE

20 / 50 page

Analog Integrated Circuit Device Data



Freescale Semiconductor

33814

General IC Functional Description and Application

Information

5.1

Functional Pin Description

5.1.1

VPWR Supply Input

The VPWR pin is the battery input to the 33814 IC. The VPWR pin requires external reverse battery and adequate transient

voltage protection. All IC analog current and internal logic current is provided from the VPWR pin.

An over-voltage comparator monitors this pin and when an over-voltage condition is present all outputs and voltage regulators

are shut off for protection. The VPWR pin should be bypassed to ground, as close to the IC as possible, with a 0.1 µF ceramic

capacitor.

5.1.2

VPPREF Output

The VPPREF output pin is used to drive the base of an external regulator PNP pass transistor. The output of this VPP regulator

supplies the input voltage to the two internal 5.0 Volt regulators. The VPP regulator is a low drop-out (LDO) regulator that provides

a regulated output voltage when the input is greater than its specified voltage level, and follows the input voltage when it is below

its specified voltage level. It is not recommended that this voltage be brought off of the module PC board, because it may not

have adequate protection to prevent damage to the PNP pass transistor under short-to-ground or short-to-battery conditions.

5.1.3

VPPSENS Input

The VPPSENS pin is used to monitor the VPP pre-regulator output voltage from the external pass transistor’s collector, and to

supply the input voltage to the VCC and VPROT regulators.

The VPPSENS pin should be bypassed to ground, as close to the IC as possible, with a 0.1 µF ceramic capacitor and a higher

value electrolytic capacitor in parallel.

5.1.4

VCC Output (5.0 V Supply)

The VCC regulator obtains its input voltage from the VPP pre-regulator. The VCC output supplies 5.0 V power to the system MCU

and other on-board peripherals.

A Power On Reset (POR) circuit monitors the VCC output voltage level. When the VCC voltage exceeds the VCC(POR) threshold,

the RESETB line is held low for an additional delay time, t(POR), and then brought to a logic one level.

An under-voltage (UV) circuit monitors the output of the VCC regulator and when the voltage goes below the VCC(UV) threshold

for more than the VCC filter time, t(VCC-UV), the RESETB line is asserted to a logic zero state and remains there until the POR

condition is met.

5.1.5

VPROT Output (5.0 V Protected Supply)

The VPROT regulator obtains its input voltage from the VPP pre-regulator and its reference voltage from the VCC output. VPROT

tracks VCC and is protected against shorts to ground, shorts to battery, over-current and over-temperature.The VPROT output

supplies 5.0 V power to any external sensors and other off-board peripherals. The VPROT regulator on/off state can be controlled

via a bit in the SPI Control Registers. The VPROT output should be protected against ESD by means of a 0.1 µF ceramic

capacitor on the output and a higher value electrolytic capacitor in parallel.

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