DRV411_15 Datasheet, PDF (20/34 Pages) Texas Instruments – Sensor Signal Conditioning IC for Closed-Loop Magnetic Current Sensors

DRV411
SBOS693B – AUGUST 2013 – REVISED DECEMBER 2013
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POWER-ON STARTUP AND BROWNOUT
Power-on is detected when the supply voltage exceeds 2.4 V at VDD. At this point, digital logic starts up and
waits for 100 µs for the excitation source to settle to its final value. During this period, ICOMP1 and ICOMP2
outputs are pulled low, so that there is no undesired signal drive on the compensation coil. Also, the error
conditions are suppressed and the ERROR pin is asserted low for 100 µs. This ensures that the excitation
voltage has reached the final level and there is no false error triggered on the output. The output on the VOUT
terminal is only valid 100 µs after power-on reset.
The DRV411 tests for low supply voltages with a brownout voltage level of +2.4 V. Good power-supply and low
ESR bypass capacitors are required to maintain the supply voltage during the large current pulses driven by the
DRV411. Supply voltage drops below the brown-out level lasting less than 25 μs are ignored. A supply drop
lasting longer than 25 μs generates power-on reset. A voltage dip on VDD down to +1.8 V also initiates a power-
on reset. After the power supply returns to 2.4 V (see the power-on reset threshold parameter in the Electrical
Characteristics), the device initiates a startup cycle as previously described.
ERROR CONDITIONS
In addition to the overrange flag that indicates signal clipping in the output amplifier (differential amplifier), a
system error flag is provided. The error flag indicates conditions when the output voltage does not represent the
primary current. The error flag is active during a power fail or brown-out, or when the Hall sensor offset becomes
greater than 50 mV, which usually means that the Hall sensor is not functioning within its normal operating
range. The error flag also goes active with an open circuit in the Hall sensor connection. As soon as the error
condition is no longer present and the circuit has returned to normal operation, the flag resets.
Both the error and overrange flags are open-drain logic outputs. They can be connected together for a wired-OR,
and require an external pull-up resistor for proper operation.
The following conditions result in error flag activation (ERROR asserts low):
1. For 100 µs from power-up, or if a supply-voltage low (brown-out) condition lasts for more than 25 μs.
Recovery is the same as power-up.
2. If the Hall sensor offset becomes greater than 50 mV.
3. If one or more of the Hall sensor terminals is disconnected.
PROTECTION RECOMMENDATIONS
The inputs IAIN1 and IAIN2 require external protection to limit the voltage swing below 6 V of the supply voltage.
Driver outputs ICOMP1 and ICOMP2 can handle high-current pulses protected by internal clamp circuits to the
supply voltage. If large magnitude overcurrents are expected, it is highly recommended to connect external
Schottky diodes to the supply rails. This external protection prevents current flowing into the die and destroying
the circuitry.
All other pins offer standard protection; see the Absolute Maximum Ratings table.
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