33730 datasheet(19/27 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33730

FUNCTIONAL DEVICE OPERATION

OPERATION DESCRIPTION

REGON

The REGON feature permits the microcontroller to select

a delayed shutdown of the 33730. It holds off the activation of

the reset signals to the microcontroller after the VIGN signal

has transitioned. This allows the microcontroller to control the

power up and power down of the main regulator outputs

except for the standby supplies. The REGON pin input

threshold voltages allow control by the standard 2.5V (up to

5V) logic ICs.

HARDWARE RESETS (RSTL, RST3, RSTH, and

RSTKAM)

The Hardware Resets are open drain, active low outputs

capable of sinking 5mA current and able to withstand +7.0V.

The RSTL control circuit monitors the VDDL output. If the

VDDL output is out of regulation (low), the device will assert

the RSTL signal low.

The RST3 control circuit monitors the VDD3 output. If the

VDD3 output is out of regulation (low), the device will assert

the RST3 signal low.

The RSTH control circuit monitors the VDDH output. If the

VDDH output is out of regulation (low or high), the device will

assert the RSTH signal low.

The RSTKAM control circuit monitors the VKAM output. If

the VKAM output is out of regulation (low), the device will

assert the RSTH signal low.

All Reset monitoring circuits have a 20

μs delay filter to

avoid unintended resets caused by noise glitches on the

regulator output lines.

HR TIMER

The HR (Hardware Reset) Timer provides the delay

between the time when the particular regulator output voltage

is in regulation and the release of the Reset signal. This delay

can be programmed by a single external resistor. This

solution provides better accuracy than the commonly used

external RC timer. The HR Timer delay can be programmed

in eight 8ms steps from 0 to 56ms (see Table 7)

Figure 6. Battery Voltage Ramp Up

Table 7. HR Timer Delay Programming

Programming Resistor

Value RHRT [ohms]

Delay (typ.)

[ms]

68k

33k

16k

8.2k

3.9k

2.0k

1.0k

470

VKAM =1.0V

Battery

Voltage

RSTKAM

POR Delay

RST L, RST 3

POR Delay

4.5V

RSTH

POR Delay

VDDL =VDD3 =3.3V

VDDH =5.0 V

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