ADA4255ACPZ-R7 datasheet(43/64 Pages) AD

43 / 64 page

Data Sheet

ADA4255

APPLICATIONS INFORMATION

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Rev. 0 | 43 of 64

HIGH RAIL CURRENT SENSING

Figure 109 shows a high-side current sense amplifier implemented

with ADA4255. The integrated charge pump PGIA topology of the

ADA4255 allows this circuit to sense bidirectional current over a

38 V range on a single 5 V supply voltage. The low offset voltage,

low offset voltage drift, low input current, and excellent linearity

allow this configuration to achieve very high dynamic range.

While the ADA4255 features an integrated EMI filter, an additional

low-pass filter can be used externally as shown. The ADA4255 has

low input bias current and input bias offset current that minimizes

the error introduced by the input bias current flowing through the

filter resistor. The matching of the filter resistors and capacitors is

required to minimize the errors and preserve AC CMRR.

The ADA4255 on-chip diagnostics allow the user to check the

circuit connections. In current sensing applications, the circuit con-

nections are verified using the wire break detection capabilities

of the ADA4255. The WB_DETECT register flag is set if one of

the connections to the shunt resistors is missing. Finally, the CRC

check, SCLK counter, and SPI read and/or write check make the

interface more robust because any read and/or write operations

that are not valid are detected. The CRC check highlights if any

bits are corrupted when transmitted between the processor and the

ADA4255.

Figure 109. High Voltage, Bidirectional, Current Sense Application

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