P

DISS +

I

OUT

2

r

DS(on), total

DRV593

DRV594

www.ti.com

SLOS401C – OCTOBER 2002 – REVISED JULY 2010

AREF CAPACITOR

The AREF terminal is the output of an internal mid-rail voltage regulator used for the onboard oscillator and ramp

generator. The regulator may not be used to provide power to any additional circuitry. A 1 mF ceramic capacitor

must be connected from AREF to AGND for stability (see oscillator components above for AGND connection

information).

SHUTDOWN OPERATION

The DRV593 and DRV594 include a shutdown mode that disables the outputs and places the device in a low

supply current state. The SHUTDOWN pin may be controlled with a TTL logic signal. When SHUTDOWN is held

high, the device operates normally. When SHUTDOWN is held low, the device is placed in shutdown. The

SHUTDOWN pin must not be left floating. If the shutdown feature is unused, the pin may be connected to VDD.

FAULT REPORTING

The DRV593 and DRV594 include circuitry to sense three faults:

•

Overcurrent

•

Undervoltage

•

Overtemperature

These three fault conditions are decoded via the FAULT1 and FAULT0 terminals. Internally, these are open-drain

outputs, so an external pullup resistor of 5 k

Ω or greater is required.

Table 3. Fault Indicators

FAULT1

FAULT0

0

0

Overcurrent

1

0

Undervoltage

0

1

Overtemperature

1

1

Normal operation

The overcurrent fault is reported when the output current exceeds four amps. As soon as the condition is sensed,

the overcurrent fault is set and the outputs go into a high-impedance state for approximately 3 ms to 5 ms

(500 kHz operation). After 3 ms to 5 ms, the outputs are re-enabled. If the overcurrent condition has ended, the

fault is cleared and the device resumes normal operation. If the overcurrent condition still exists, the above

sequence repeats.

The undervoltage fault is reported when the operating voltage is reduced below 2.8 V. This fault is not latched,

so as soon as the power supply recovers, the fault is cleared and normal operation resumes. During the

undervoltage condition, the outputs go into a high-impedance state to prevent overdissipation due to increased

rDS(on).

The overtemperature fault is reported when the junction temperature exceeds 128°C. The device continues

operating normally until the junction temperature reaches 158°C, at which point the IC is disabled to prevent

permanent damage from occurring. The system's controller must reduce the power demanded from the DRV593

or DRV594 once the overtemperature flag is set, or else the device switches off when it reaches 158°C. This

fault is not latched; once the junction temperature drops below 128°C, the fault is cleared, and normal operation

resumes.

POWER DISSIPATION AND MAXIMUM AMBIENT TEMPERATURE

Though the DRV593 and DRV594 are much more efficient than traditional linear solutions, the power drop

across the on-resistance of the output transistors does generate some heat in the package, which may be

calculated as shown in Equation 11:

(11)

For example, at the maximum output current of 3 A through a total on-resistance of 130 m

Ω (at TJ = 25°C), the

power dissipated in the package is 1.17 W.

Calculate the maximum ambient temperature using Equation 12:

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