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NE56625-20

System reset with Watchdog timer

Philips Electronics 

Philips Semiconductors

System reset with Watchdog timer

Product data

NE56625-20

AC ELECTRICAL CHARACTERISTICS

Characteristics measured with VCC = 2.6 V, and Tamb = 25 °C, unless otherwise specified.

SYMBOL

PARAMETER

CONDITIONS

MIN. TYP. MAX. UNIT

tP1

Minimum power supply pulse width for

4.0 V ≤ negative-going VCC pulse ≤ 5.0 V

8.0

–

–

µs

detection

tCLKW

Clock input pulse width

3.0

–

–

µs

tCLK

Clock input cycle

20

–

–

µs

tWDM

Watchdog monitoring time (Notes 1, 6)

CT = 0.022 µF; RCT = open

50

100

150

ms

tWDR

Watchdog reset time (Notes 2, 6)

CT = 0.022 µF

1.0

2.0

3.0

ms

tPR

Power-on reset delay time (Notes 3, 6)

VCC = rising from 0 V; CT = 0.022 µF

50

100

150

ms

tPDR

RESET propagation delay time (Note 4)

VCC = falling; RLR = 100 kΩ; CLR = 15 pF

–

10

–

µs

tPDB

Battery Check propagation delay time

VCC = falling; RLB = 10 kΩ; CLB = 15 pF

–

10

–

µs

(Note 4)

tRR

RESET rise time (Note 5)

RLR = 100 kΩ; CLR = 15 pF

–

10

–

µs

tFR

RESET fall time (Note 5)

RLR = 100 kΩ; CLR = 15 pF

–

2

–

µs

tRB

Battery Check rise time (Note 5)

RLB = 10 kΩ; CLB = 15 pF

–

10

–

µs

tFB

Battery Check fall time (Note 5)

RLB = 10 kΩ; CLB = 15 pF

–

2

–

µs

NOTES:

1. ‘Watchdog monitoring time’ (tWDM) is the duration from the last pulse (negative-going edge) of the timer clear clock pulse until reset output

pulse occurs (see Figure 17). A reset signal is output if a clock pulse is not input during this time.

2. ‘Watchdog reset time’ (tWDR) is the reset pulse width. Do not confuse this with the power-on reset delay time (tPR).

3. The power-on reset delay or hold time is the duration measured from the time VCC exceeds the upper detection threshold (VSHR) and

power-on reset release is experienced (RESET output HIGH).

4. ‘Reset response time’ is the duration from when the supply voltage sags below the lower detection threshold (VSL) and reset occurs (RESET

output LOW).

5. Reset rise and fall times and Battery Check rise and fall times are measured at 10% and 90% output levels.

6. Watchdog monitoring time (tWDM), Watchdog reset time (tWDR), and power-on reset delay time (tPR) during power-on can be modified by

varying the CT capacitance. The times can be approximated by applying the following formula. The recommended range for CT is 0.0022 µF

to 2.2 µF.

Formula 1.

Calculation for approximate tPR, tWDM, and tWDR values:

tPR (ms) ≈ 4500 × CT (µF)

tWDM (ms) ≈ 4500 × CT (µF)

tWDR (ms) ≈ 90 × CT (µF)

Example:

When CT = 0.022 µF and RCT = open:

tPR ≈ 100 ms

tWDM ≈ 100 ms

tWDR ≈ 2.0 ms

2003 Oct 15

5

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