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8.3.10 Current Sense Amplifiers

The DRV8317 integrates three high-performance low-side current sense amplifiers for current measurements

using built-in current sense. Low-side current measurements are commonly used to implement overcurrent

protection, external torque control, or brushless DC commutation with the external controller. Each amplifier

senses the current in the corresponding half-bridge when the low-side MOSFET is conducting. The current

sense amplifiers include features such as configurable gain (through CSA_GAIN register or GAIN pin) and an

external voltage reference (VREF) provided through CSAREF pin.

8.3.10.1 Current Sense Amplifier Operation

The SOx pin on the DRV8317 provides an analog voltage proportional to the current flowing in the low side

MOSFETs (IOUTx) multiplied by the gain setting (GCSA) of the current sense amplifier. The gain setting is

adjustable between four different levels which can be set by the GAIN pin (hardware variant) or the CSA_GAIN

Figure 8-19 shows the internal architecture of the current sense amplifiers. The current sense is implemented

with a sense FET on each low-side FET of the DRV8317 device. This current information is converted in to a

voltage based on the CSAREF pin (VREF) input and the CSA gain setting; this voltage is available on the SOx

pin. The CSA output voltage can be calculated using Equation 2

SOx = VREF/2 + (GCSA * IOUTx), wherein IOUTx is considered positive in the direction shown in Figure 8-19.

(2)

PGND

OUTx

I/V Converter

Sense

FET

GAIN

SOx

VREF

Figure 8-19. Integrated Current Sense Amplifier

Figure 8-20 shows the IOUTx to CSA output transfer function. In bi-directional operation, the amplifier output for

0-A input is set at VREF/2. Any change in the output phase current results in a corresponding change in the

amplifier output as given in Equation 2.

SOX (V)

IOUTx (A) (Current flowing out of OUTx)

VREF

VREF / 2

VLINEAR

(VREF

0.25-V

0-V

- 0.25)

Figure 8-20. IOUTx to CSA Transfer Function

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DRV8317

SLVSGT3 – DECEMBER 2022

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