DRV593_15 Datasheet, PDF (17/27 Pages) Texas Instruments – 3−A HIGH−EFFICIENCY PWM POWER DRIVER

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DRV593
DRV594
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 kΩ or greater is required.
FAULT1
0
1
0
1
Table 3. Fault Indicators
FAULT0
0
0
1
1
Overcurrent
Undervoltage
Overtemperature
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
r_DS(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:
2
ǒ Ǔ _{PDISS + IOUT}
rDS(on), _total
(11)
For example, at the maximum output current of 3 A through a total on-resistance of 130 mΩ (at T_J = 25°C), the
power dissipated in the package is 1.17 W.
Calculate the maximum ambient temperature using Equation 12:
Copyright © 2002–2010, Texas Instruments Incorporated
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