DRV401AIDWPR datasheet(21/36 Pages) TI1

21 / 36 page

DRV401

SBVS070B − JUNE 2006 − REVISED MAY 2009

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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):

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 ICOMP driver

remains active but goes inactive thereafter. In case of

recovery, ERROR is low and the ICOMP driver remains

in reset for another 3.3ms.

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 25

µs and then recovers, the ERROR flag

remains low and ICOMP is in reset for another 3.3ms.

If the condition lasts less than 25

µs, the ERROR flag

recovers immediately and the ICOMP driver is not

interrupted.

During demagnetization, if the cycle is aborted early

by pulling DEMAG low, the ERROR flag stays low for

another 3.3ms (ICOMP is disabled during this time).

An open compensation coil is detected (longer than

100

µs). Note: the probe driver, the PWM signal

filter and the ICOMP 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 ICOMP 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.

At power-on after VDD1 crosses the +4V threshold,

the ERROR flag is low for approximately 42

µs.

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 IAIN1 and IAIN2 require external protection to

limit the voltage swing beyond 10V of the supply voltage.

The driver outputs ICOMP1 and ICOMP2 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.

DRV401AIDWPR Datasheet(PDF) 21 Page - Texas Instruments

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