ZHCSJX5 June 2019 ADS7028
ADVANCE INFORMATION for pre-production products; subject to change without notice.
The channels of the ADS7028 can be configured as digital open-drain outputs supporting an output voltage up to 5.5 V. An open-drain output, as shown in Figure 139, consists of an internal FET (Q) connected to ground. The output is idle when not driven by the device, which means Q is off and the pullup resistor, RPULL_UP, connects the GPOx node to the desired output voltage. The output voltage can range anywhere up to 5.5 V, depending on the external voltage that the GPIOx is pulled up to. When the device is driving the output, Q turns on, thus connecting the pullup resistor to ground and bringing the node voltage at GPOx low.
The minimum value of the pullup resistor, as calculated in Equation 6, is given by the ratio of VPULL_UP and the maximum current supported by the device digital output (5 mA).
The maximum value of the pullup resistor, as calculated in Equation 7, depends on the minimum input current requirement, ILOAD, of the receiving device driven by this GPIO.
Select RPULL_UP such that RMIN < RPULL_UP < RMAX.