DRV8305_15 Datasheet, PDF (42/53 Pages) Texas Instruments – DRV8305 Three Phase Gate Driver With Current Shunt Amplifiers and Voltage Regulator

DRV8305
SLVSCX2A – AUGUST 2015 – REVISED SEPTEMBER 2015
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Example: 0.197 V (VDS_LVL) / 4.1 mΩ (R_DS(ON)) = 48 A
8.2.2.4 Current Sense Amplifiers
The DRV8305 provides three bidirectional low-side current shunt amplifiers. These can be used to sense the
current flowing through each half-bridge. If individual half-bridge sensing is not required, a single current shunt
amplifier can be used to measure the sum of the half-bridge current. Use this simple procedure to correctly
configure the current shunt amplifiers.
1. Determine the peak current that the motor will demand (IMAX). This demand depends on the motor
parameters and the application requirements. IMAX in this example is 14 A.
2. Determine the available voltage output range for the current shunt amplifiers. This will be the ± voltage
around the amplifier bias voltage (VBIAS). In this case VBIAS = 1.65 V and a valid output voltage is 0 to 3.3
V. This gives an output range of ±1.65 V.
3. Determine the sense resistor value and amplifier gain settings. The sense resistor value and amplifier gain
have common tradeoffs. The larger the sense resistor value, the better the resolution of the half-bridge
current. This comes at the cost of additional power dissipated from the sense resistor. A larger gain value
allows for the use of a smaller resolution, but at the cost of increased noise in the output signal and a longer
settling time. This example uses a 5-mΩ sense resistor and the minimum gain setting of the DRV8305 (10
V/V). These values allow the current shunt amplifiers to measure ±33 A across the sense resistor.
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