DRV8303_15 Datasheet, PDF (14/37 Pages) Texas Instruments – Three Phase Gate Driver

DRV8303
SLOS846B – SEPTEMBER 2013 – REVISED NOVEMBER 2015
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7.3.2 Current Shunt Amplifiers
The DRV8303 includes two high performance current shunt amplifiers to accurate low-side, inline current
measurement.
The current shunt amplifiers have 4 programmable GAIN settings through the SPI registers. These are 10, 20,
40, and 80 V/V.
They provide output offset up to 3V to support bidirectional current sensing. The offset is set to half the voltage
on the reference pin (REF).
To minimize DC offset and drift over temperature a calibration method is provided through either the DC_CAL pin
or SPI register. When DC calibration is enabled, the device will short the input of the current shunt amplifier and
disconnect the load. DC calibration can be done at any time, even during MOSFET switching, because the load
is disconnected. For the best results, perform the DC calibration during the switching OFF period, when no load
is present, to reduce the potential noise impact to the amplifier.
The output of the current shunt amplifier can be calculated as:
V_O = ^VREF - G ´ (SN_X - SP_X )
2
where
•
•
•
VREF is the reference voltage (REF pin)
G is the gain of the amplifier (10, 20, 40, or 80 V/V)
SNX and SPx are the inputs of channel x. SPx should connect to the ground side of the sense resistor for the
nest common mode rejection.
(1)
Figure 6 shows the current amplifier simplified block diagram.
400kW
S4
DC_CAL
SN
200kW
S3
100kW
S2
50kW
S1
5kW
_
AVDD
DC_CAL
100W
SO
5kW
+
SP
DC_CAL
50kW
S1
100kW
S2
200kW
S3
400kW
S4
Vref/2
REF
_
AVDD
50kW
+
50kW
Figure 6. Current Shunt Amplifier Simplified Block Diagram
14
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