DRV401-EP Datasheet, PDF (23/33 Pages) Texas Instruments – SENSOR SIGNAL CONDITIONING IC FOR CLOSED-LOOP MAGNETIC CURRENT SENSOR

DRV401-EP
www.ti.com............................................................................................................................................................................................... SBVS104 – JANUARY 2008
ERROR CONDITIONS
In addition to the Over-Range 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. It is active during a demagnetization cycle, during a power-fail or brown-out. It also goes
active with an open or short-circuit in the probe loop. 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 Over-Range 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. The probe comparator stays low for more than 32 µs. This condition occurs either if the probe coil connection
is open or if the supply voltage dips to the level where the required saturation current cannot be reached.
During the 32 µs timeout, the I_COMP driver remains active but goes inactive thereafter. In case of recovery,
ERROR is low and the ICOMP driver remains in reset for another 3.3 ms.
2. The probe driver pulse-width is less than 280 ns for three consecutive periods. This condition indicates either
a shorted field probe coil or a fully-saturated sensor at start-up. If this condition persists longer than 25 µs
and then recovers, the ERROR flag remains low and ICOMP is in reset for another 3.3 ms. If the condition
lasts less than 25 µs, the ERROR flag recovers immediately and the I_COMP driver is not interrupted.
3. During demagnetization, if the cycle is aborted early by pulling DEMAG low, the ERROR flag stays low for
another 3.3 ms (I_COMP is disabled during this time).
4. An open compensation coil is detected (longer than 100 µs). Note: the probe driver, the PWM signal filter
and the I_COMP driver continue to function in normal mode—only the ERROR flag is asserted in this case. This
condition indicates that not enough current is flowing in the I_COMP driver output; this condition might be the
result of a high-resistance compensation coil or the connection of an external driver. Detection of this
condition can be disabled by setting the CCdiag pin low.
5. At power-on after V_DD1 crosses the +4 V threshold, the ERROR flag is low for approximately 42 µs.
6. A supply voltage low (brown-out) condition lasts longer than 100 µs. Recovery is the same as power-up,
either with or without a demag cycle.
PROTECTION RECOMMENDATIONS
The inputs IA_IN1 and IA_IN2 require external protection to limit the voltage swing beyond 10 V of the supply voltage.
The driver outputs I_COMP1 and I_COMP2 can handle high current pulses protected by internal clamp circuits to the
supply voltage. If repeated over-currents of large magnitudes are expected, connect external Schottky diodes to
the supply rails. This external protection prevents current flowing into the die.
The probe connections IS1 and IS2 are protected with diode clamps to the supply rails. In normal applications,
no external protection is required. The maximum current must be limited to ±75 mA.
All other pins offer standard protection-see the Absolute Maximum Ratings table.
Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): DRV401-EP
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