HT49CV3 datasheet(25/44 Pages) HOLTEK

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HT49RV3/HT49CV3

Rev. 1.30

March 20, 2007

V D D

5 . 5 V

V L V R

0 . 9 V

0 V

R e s e t S i g n a l

R e s e t

* 1

* 2

N o r m a l O p e r a t i o n

R e s e t

L V R D e t e c t V o l t a g e

Low Voltage Reset

Note: *1: To make sure that the system oscillator has stabilized, the SST provides an extra delay of 1024 system

clock pulses before starting normal operation.

*2: Since the low voltage has to maintain its original state for longer than 1ms, therefore a 1ms delay enters the

reset mode.

Low Voltage Reset

There is a low voltage reset circuit (LVR) implemented in

the microcontroller. This function can be enabled/dis-

abled by options.

If the supply voltage of the device is within the range

0.9V~VLVR, such as when changing a battery, the LVR

will automatically reset the device internally.

The LVR includes the following specifications:

· The low voltage (0.9V~V

LVR) has to remain in its origi-

nal state for longer than 1ms. If the low voltage state

does not exceed 1ms, the LVR will ignore it and will

not perform a reset function.

· The LVR uses an

²OR² function with the external RES

signal to perform a chip reset.

The relationship between VDD and VLVR is shown below.

Note: VOPR is the voltage range for proper chip

operation at 4MHz system clock.

5 . 5 V

3 . 0 V

2 . 2 V

0 . 9 V

V D D

V O P R

V L V R

5 . 5 V

HT49CV3 Datasheet(PDF) 25 Page - Holtek Semiconductor Inc

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