L497 datasheet(3/11 Pages) STMICROELECTRONICS

3 / 11 page

PIN FUNCTIONS (refer to fig. 4)

Name

Function

GND

This pin must be connected to ground.

SIGNAL GND

This pin must be connected to ground.

POWER SUPPLY

Supply Voltage Input. An internal 7.5 V (typ) zener zener limits the voltage

at this pin. The external resistor R5 limits the current through the zener for

high supply voltages.

N.C.

This pin must be connected to ground or left open.

HALL-EFFECT INPUT

Hall-effect Pickup Signal Input. This input is dwell control circuit output in

order to enable the current driving into the coil. The spark occurs at the

high-to-low transition of the hall-effect pickup signal.

Furthermore this input signal enables the slow recovery and permanent

conduction protection circuits. The input signal, supplied by the open

collector output stage of the Hall effect sensor, has a duty-cycle typically

about 70 %. V5 is internally clamped to V3 and ground by diodes

RPM OUTPUT

Open collector output which is at a low level when current flows in the

ignition coil. For high voltages protection of this output, connection to the

pin 7 zener is recommended.

In this situation R8 must limit the zener current, too, and R1 limits pin 6

current if RPM module pad is accidentally connected to VS.

AUX. ZENER

A 21 V (typ) General Purpose Zener. Its current must be limited by an

external resistor.

RECOVERY TIME

A capacitor connected between this pin and ground sets the slope of the

dwell time variation as it rises from zero to the correct value. This occurs

after the detection of Icoll

≤ 94 % Inom, just before the low transition of the

hall-effect signal pulse.

The duration of the slow recovery is given by :

tsrc = 12,9 R7 Csrc (ms)

where R7 is the biasing resistor at pin 12 (in K

Ω) and Csrc is the delay

capacitor at pin 8 (in

µF).

MAX CONDUCTION

TIME

A capacitor connected between this pin and ground determines the

intervention delay of the permanent conduction protection. After this delay

time the coil current is slowly reduced to zero.

Delay Time Tp is given by :

Tp =16 Cp R7 (ms)

where R7 is the biasing resistor at pin 12 (in K

Ω) and CP is the delay

capacitor at pin 9 (in

µF).

DWELL CONTROL

TIMER

A capacitor CT connected between this pin and ground is charged when the

HAll effect output is High and is discharged at the High to Low transition of

the Hall effect signal.

The recommended value is 100 nF using a 62 K

Ω resistor at pin 12.

DWELL CONTROL

The average voltage on the capacitor CW connected between this pin and

ground depends on the motor speed and the voltage supply. The

comparison between VCW and VCT voltage determines the timing for the

dwell control. For the optimized operation of the device CT =CW; the

recommended value is 100 nF using a 62 K

Ω resistor at pin 12.

BIAS CURRENT

A resistor connected between this pin and ground sets the internal current

used to drive the external capacitors of the dwell control

(pin 10 and 11) permanent conduction protection (pin 9) and slow recovery

time (pin 8). The recommended value is 62 K

Ω.

CURRENT SENSING

Connection for the Coil Current Limitation. The current is measured on the

sensing resitor RS and taken through the divider R10/R11. The current

limitation value is given by :

Isens

= 0.32

⋅

R10

+ R11

⋅ R11

L497

3/11

L497 数据表(PDF) 3 Page - STMicroelectronics

L497 数据表(HTML) 3 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11

数据表下载