ZHCSQ83A March 2022 – October 2022 INA851
PRODUCTION DATA
The INA851 features a unique output clamping function that protects the downstream device against damage that results from inadvertent over-driving. Usually the downstream device is an ADC that typically operates at a lower supply voltage than the INA851.
To implement this function, use the VCLAMP+ and VCLAMP– pins to limit the supply voltage range of the differential output drive amplifier. For typical operation, use a low-impedance connection from the pins to the power supplies of the ADC. For proper operation of the clamp circuitry, set the VS+ or VS– supply voltages at least 1.5 V beyond the respective VCLAMP+ and VCLAMP– clamping voltages. In addition, for the output driver to function correctly, the VCLAMP+ and VCLAMP– voltages must be at least 3 V apart. If the output clamping functionality is not desired, short the VCLAMP+ and VCLAMP– pins to the amplifier VS+ and VS– supply pins.
The output driver operates up to the VCLAMP+ or VCLAMP– limits without experiencing distortion. When the clamping function is in use the output voltage is clamped at approximately 600 mV beyond the clamp voltage.), so that the device output spans the full input range of the ADC. However, if the predriver output swings beyond the VCLAMP+ or VCLAMP– voltage, the output driver begins to run out of headroom as a result of the clamped supply voltage, shown in Figure 8-12.
The output is unable to swing greater than approximately 500 mV beyond the VCLAMP+ or VCLAMP– voltage (at zero load), helping prevent or reduce damage to the ADC from overvoltage conditions.
The linear operation becomes distorted when the driver load becomes higher than 20 mA, see Figure 8-13.
The VCLAMP+ pin features a fail-safe against power-up sequencing issues between the INA851 and a downstream device. For example, a condition of V(CLAMP+) + 10 V on this pin does not cause damage. Therefore, the ADC supply can safely turn on while the INA851 supply is still off or just beginning to turn on. In this case, the current draw through the VCLAMP+ pin is limited to a safe value of typically 3 mA.