L9997 データシートの表示（PDF） - STMicroelectronics

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L9997

DUAL HALF BRIDGE DRIVER

STMicroelectronics 

L9997ND

The device is activated with enable input voltage

HIGH. For enable input floating (not connected)

or LOW the device is in Standby Mode. Very low

quiescent current is defined for VEN < 0.3V. When

activating or disactivating the device by the en-

able input a wake-up time of 50µs is recom-

mended.

For braking of the motor the status 2 is recom-

mended. The reason for this recommendation is

that the device features higher threshold for ini-

tialisation of parasitic structures than in state 5.

The inputs IN1, IN2 features internal sink current

generators of 10µA, disabled in standby mode.

With these input current generators the input level

is forced to LOW for inputs open. In this condition

the outputs are in SNK state.

The circuit features an overvoltage disable func-

tion referred to the supply voltage VVS. This func-

tion assures disabling the power outputs, when

the supply voltage exceeds the over voltage

threshold value of 19V typ. Both outputs are

forced to tristate in this condition and the diagnos-

tic output is ON.

The thermal shut-down disables the outputs (tris-

tate) and activates the diagnostic when the junc-

tion temperature increases above the thermal

shut-down threshold temperature of min. 150°C.

For the start of a heavy loaded motor, if the motor

current reaches the max. value, it is necessary to

respect the dynamical thermal resistance junction

to ambient. The outputs OUT1 and OUT2 are pro-

tected against short circuit to GND or VS, for sup-

ply voltages up to the overvoltage disable thresh-

old.

The output power DMOS transistors works in lin-

ear mode for an output current less than 1.2A. In-

creasing the output load current (> 1.2A) the out-

put transistor changes in the current regulation

mode, see Fig.6, with the typical output current

value below 2A. The SRC output power DMOS

transistors requires a voltage drop ~3V to activate

the current regulation. Below this voltage drop is

the device also protected. The output current heat

up the power DMOS transistor, the RDSON in-

creases with the junction temperature and de-

creases the output current. The power dissipation

in this condition can activate the thermal shut-

down . In the case of output disable due to ther-

mal overload the output remains disabled untill

the junction temperature decreases under the

thermal enable threshold.

Permanent short circuit condition with power dis-

sipation leading to chip overheating and activation

of the thermal shut-down leads to the thermal os-

cillation. The junction temperature difference be-

tween the switch ON and OFF points is the ther-

mal hysteresis of the thermal protection. This

hysteresis together with the thermal impedance

and ambient temperature determines the fre-

quency of this thermal oscillation, its typical val-

ues are in the range of 10kHz.

The open drain diagnostic output needs an exter-

nal pull-up resistor to a 5V supply. In systems

with several L9997ND the diagnostic outputs can

be connected together with a common pull-up re-

sistor. The DIAG output current is internally lim-

ited.

Fig. 1 shows a typical application diagram for the

DC motor driving. To assure the safety of the cir-

cuit in the reverse battery condition a reverse pro-

tection diode D1 is necessary. The transient pro-

tection diode D2 must assure that the maximal

supply voltage VVS during the transients at the

VBAT line will be limited to a value lower than the

absolute maximum rating for VVS.

Figure 1: Application Circuit Diagram.

5V

47KΩ

IDIAG1

DIAG1

CONTROL

LOGIC

IIN1

IN1

IIN2

IN2

IEN

EN

Is

VS

L9997ND

CS

OUT1

IOUT1

D1

D2

VBAT

IM

VM

M

OUT2

GND

IOUT2

GND

4/9

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