DS3717 Rev 12

9/22

L4979D-E, L4979MD

Electrical specifications

21

Res

R_p_u

Internal pull-up

resistance

With respect to Vo

12

25

50

k



Res

Vo_th

Reset threshold voltage

Vs = 5.6 to 31 V

Io = 1 to 150 mA

6%

below

Vo_ref

8%

below

Vo_ref

10%

below

Vo_ref

Vcr

Vrhth

Reset timing high

threshold

Vs = 13.5 V

44%

Vo_ref

47%

Vo_ref

50%

Vo_ref

Vcr

Vrlth

Reset timing low

threshold

Vs = 13.5 V

10%

Vo_ref

13%

Vo_ref

16%

Vo_ref

Vcr

Icr

Charge current

Vs = 13.5 V

8

17

30

µA

Vcr

Idr

Discharge current

Vs = 13.5 V

8

17

30

µA

Res

trr_2

Reset delay time(1)

Vo = Vo_th - 100 mV

100

250

700

µs

Res

trd

Reset pulse delay

Vs = 13.5 V; Ctr = 1 nF

65

150

ms

1. When Vo becomes lower than 4 V, the reset reaction time decreases down to 2 µs assuring a faster reset

condition in this particular case.

Table 8. Watchdog

Pin

Symbol

Parameter

Test condition

Min.

Typ.

Max.

Unit

Wi

Vih

Input high voltage

Vs = 13.5 V

3.5

V

Wi

Vil

Input low voltage

Vs = 13.5 V

1.5

V

Wi

Vih

Input hysteresis

Vs = 13.5 V

300

mV

Wi

Ii

Pull down current

Vs = 13.5 V

10

20

µA

Vcw

Vwhth

High threshold

Vs = 13.5 V

2.20

2.35

2.50

V

Vcw

Vwlth

Low threshold

Vs = 13.5 V

0.50

0.65

0.80

V

Vcw

Icwc

Charge current

Vs = 13.5 V; Vcw = 0.1 V

4

7.5

14

µA

Vcw

Icwd

Discharge current

Vs = 13.5 V; Vcw = 2.5 V

1.0

2.4

4.5

µA

Vcw

Twop

Watchdog period

Vs = 13.5 V;

Ctw = 47 nF

25

50

90

ms

Res

twol

Watchdog output low

time

Vs = 13.5 V;

Ctw = 47 nF

6

10

22

ms

Table 7. Reset (continued)

Pin

Symbol

Parameter

Test condition

Min.

Typ.

Max.

Unit