7.3.2 Constant-Current Driver

The TPS92612 device is a high-side constant-current driver. The device controls the output current through regulating the voltage drop on an external high-side current-sense resistor, R_(SNS). An integrated error amplifier drives an internal power transistor to maintain the voltage drop on the current-sense resistor R_(SNS) to V_{(CS_REG)} and therefore regulates the current output to target value. When the output current is in regulation, the current value can be calculated by using Equation 1.

Equation 1.

where

• V_{(CS_REG)} = 98 mV (typical)

When the SUPPLY-to-OUT voltage difference is below the required dropout voltage, V_(DROPOUT), at a given output current, the TPS92612 is not able to deliver enough current output as set by the value of R_(SNS), and the voltage across the current-sense resistor R_(SNS) is less than V_{(CS_REG)}.