MTS2916A datasheet(10/20 Pages) MICROCHIP

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MTS2916A

DS22259C-page 10

 2010-2013 Microchip Technology Inc.

When the maximum allowed current is reached, the

bridge source is turned off during a fixed period TOFF

(typically 50 µs) given by a non-retriggerable pulse

generator and the external timing components Rt

(20k-100 k

 range) and C

t (100 pF-1000 pF range):

EQUATION 3-2:

During TOFF, the winding current decreases. When the

driver is re-enabled, the winding current increases

again until it reaches the threshold, and the cycle

repeats itself, maintaining the load current at the

desired level.

FIGURE 3-3:

PWM Output Current

Waveform.

3.3

Circuit Protection

A thermal protection circuitry turns off all drivers when

the junction temperature exceeds a safe operating limit

of +170°C (typical). This protects the devices from

failure due to excessive heating. Despite this thermal

protection, output short circuits are not permitted. The

output

drivers

are

re-enabled

once

junction

temperature has dropped below +145°C (typical).

FIGURE 3-4:

Thermal Shutdown Output

vs. Temperature Showing Hysteresis.

An undervoltage lockout circuit protects the MTS2916A

from potential shoot-through currents when the load

supply voltage is applied prior to the logic supply volt-

age. The power bridge and all outputs are disabled if

VLOGIC is smaller than 4V.

With this protection feature, the circuit will withstand

any order of turn-on or turn-off of the supply voltages

VLOGIC and VLOAD. Normal dV/dt values are assumed.

OFF

1.1







PHASE

IOUT

toff

ton

+170°C

+145°C

thshtd_en

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