DocID026400 Rev 1

11/21

L9915

Electrical specification

20

Cranking security function

Figure 5. Cranking security function diagram

At the ignition key on the device (i.e. "key" switch closed in the application schematic) starts

in pre-excitation; in this phase the battery voltage is over both VBUV and VBLOW and the

pin F provides a fixed duty cycle. When the starter is engaged, the battery sources a big

current and then the applied voltage on the device decreases, as reported in ISO 7637-1

pulse 4 specification. If the voltage on pin B decreases under VBLOW threshold then the

device is frozen: the device is in low current consumption with no activity on both F and FM

pins, only the L pin is able to turn on the lamp.

The device remains in frozen condition until the voltage on B overcomes the VBUV

threshold, after that, the device is able again to evaluate the inputs coming from both PH

and C pins.

3.3.2

Pin "C"

Table 7. Electrical characteristics - Pin "C"

Symbol

Parameter

Test condition

Min

Typ

Max

Unit

Internal regulated power

supply

-

6.2

6.8

7.3

V

Pull-up resistor

-

1.75

3.5

5.7

k



High level threshold voltage

-

3.1

3.3

3.5

V

Low level threshold voltage

-

1.3

1.5

1.7

V

Valid frequency range

-

100

-

500

Hz

Low not valid frequency

range

--

-

74

Hz

High not valid frequency

range

-

676

-

-

Hz

Delay time to switch from

external to Internal regulation

-

30

50

100

ms

-

9

-

93

%