DRV401-Q1 Datasheet, PDF (20/39 Pages) Texas Instruments – DRV401-Q1 Sensor Signal Conditioning Device for Closed-Loop Magnetic Current Sensor

DRV401-Q1
SBOS814 – DECEMBER 2016
www.ti.com
Feature Description (continued)
7.3.5 Shunt Sense Amplifier
The differential (H-bridge) driver arrangement for the compensation coil requires a differential sense amplifier for
the shunt voltage. This differential amplifier offers wide bandwidth and a high slew rate for fast current sensors.
Excellent dc stability and accuracy result from an auto-zero technique. The voltage gain is 4 V/V, set by precisely
matched and stable internal SiCr resistors.
7.3.6 Over-Range Comparator
High peak current can overload the differential amplifier connected to the shunt. The OVER-RANGE pin, an
open-drain output, indicates an over-voltage condition for the differential amplifier by pulling low. The output of
this flag is suppressed for 3 μs, preventing unwanted triggering from transients and noise. This pin returns to high
when the overload condition is removed (an external pull-up is required to return the pin high).
This ERROR flag provides a warning about a signal clipping condition, but is also a window comparator output
for actively shutting off circuits in the system. The value of the shunt resistor defines the operating window for the
current. The value of the shunt resistor sets the ratio between the nominal signal and the trip level of the over-
range flag. The trip current of this window comparator is calculated using the following example:
With a 5-V supply, the output voltage swing is approximately ±2.45 V (load and supply voltage-dependent).
The gain of 4 V/V allows an input swing of ±0.6125 V.
Thus, the clipping current is I_MAX = 0.6125 V / R_SHUNT.
See Figure 10.
The over-range condition is internally detected when the amplifier exceeds the linear operating range, not merely
as a set voltage level. Therefore, the error or the over-range comparator level is reliably indicated in fault
conditions such as output shorts, low load or low supply conditions. The flag is activated when the output cannot
drive the voltage higher. The configuration is a safety improvement over a voltage level comparator.
NOTE
The internal resistance of the compensation coil may prevent high compensation current
from flowing because of I_COMP driver overload. Therefore, the differential amplifier may not
overload with this current. However, a fast rate of change of the primary current would be
transmitted through transformer action and safely trigger the overload flag.
20
Submit Documentation Feedback
Product Folder Links: DRV401-Q1
Copyright © 2016, Texas Instruments Incorporated