DRV401_15 Datasheet, PDF (21/36 Pages) Texas Instruments – Sensor Signal Conditioning IC for Closed-Loop Magnetic Current Sensor

DRV401
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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 32µs.
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 32µs timeout, the I_COMP driver
remains active but goes inactive thereafter. In case of
recovery, ERROR is low and the I_COMP driver remains
in reset for another 3.3ms.
2. The probe driver pulse-width is less than 280ns 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 25µs and then recovers, the ERROR flag
remains low and I_COMP is in reset for another 3.3ms.
If the condition lasts less than 25µs, 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 3.3ms (I_COMP is disabled during this time).
SBVS070B − JUNE 2006 − REVISED MAY 2009
4. An open compensation coil is detected (longer than
100µs). 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 +4V threshold,
the ERROR flag is low for approximately 42µs.
6. A supply voltage low (brown-out) condition lasts
longer than 100µs. 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 10V 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 ±75mA.
All other pins offer standard protection—see the Absolute
Maximum Ratings table.
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