COM-VEE output takes VDD-VEE output as its input and creates a regulated output voltage. It can be considered as an LDO output from VDD-VEE, though the operation principle is not quite the same. Given its input voltage is VDD-VEE, the maximum output voltage from COM to VEE is the voltage between VDD and VEE.

The COM-VEE output regulator stage uses the internal high-side or low-side FETs in series with the external current-limit resistor (R_LIM) to charge or discharge the COM-VEE output voltage. The hysteresis control is used to control the switching instance of the two FETs, to achieve an accurately regulated COM-VEE voltage. As shown in Figure 7-2, the COM-VEE output voltage is sensed through the voltage divider R_{FBVEE_TOP} and R_{FBVEE_BOT} on FBVEE pin. TI recommends a 330-pF capacitor on FBVEE pin to filter out the switching frequency noise. When the voltage on FBVEE is below the charging threshold, 20 mV below the V_{FBVEE_REF}, the charging resistor is kept on and discharging resistor is kept off. COM-VEE output voltage rises. After FBVEE voltage reaches the stop charging threshold, 20 mV above the V_{FBVEE_REF}, the charging resistor is turned off. Output voltage rise stops. When the charging resistor is turned off, the discharge resistor is controlled by another hysteresis controller, based on FBVEE pin voltage, with the same reference voltage V_{FBVEE_REF}, and 20-mV of hysteresis.

The COM-VEE output regulator stage will protect from having the high-side FET stay ON for a long time during a COM to VEE short. This protection feature is implemented by monitoring the RLIM-pin voltage and controlling the high-side FET duty-ratio. When the COM pin voltage is lower than 0.645 V while the FBVEE voltage is below 2.48 V, the hysteretic control of the COM-VEE regulator is overridden by an approximately 20 % duty-ratio control on high-side FET, with a typical on-time of 1.2 μs and off-time of 5 μs in each duty cycle. When the COM pin voltage is higher than 0.73 V, the duty ratio control is disabled and the hysteretic control resumes to normal operation.