SNVSBU3 March 2021 LP87702
The LP87702 device has programmable voltage monitoring for the BUCKx and BOOST converter output voltages and for VANA, VMON1, and VMON2 inputs. Monitoring of each signal is independently enabled in the PGOOD_CTRL register. Voltage monitoring can be under-voltage monitoring only (PGOOD_WINDOW = 0) or overvoltage and undervoltage monitoring (PGOOD_WINDOW = 1). This selection is common for all enabled monitorings. Section 18.104.22.168describes how the enabled monitoring signals are combined to generate power-good (PG0 and PG1) and interrupts. Monitoring comparators have a dedicated reference and bias block, which is independent of the main reference and bias block.
Nominal level for the output voltage of BUCKx converter is set with BUCKx_VSET in the BUCKx_VOUT register. Overvoltage and undervoltage detection levels, with respect to nominal level, are selected with BUCKx_WINDOW as ± 30 mV, ± 50 mV, ± 70 mV or ± 90 mV. Nominal level for the output voltage of the BOOST converter is set with BOOST_VSET in the BOOST_CTRL register. Available levels are 4.9 V, 5 V, 5.1 V, and 5.2 V. Overvoltage and undervoltage detection levels, with respect to nominal level, are selected with BOOST_WINDOW as ± 2%, ± 4%, ± 6% or ± 8%. Converter monitoring window selection bits are in the PGOOD_LEVEL_3 register.
Input voltage of LP87702 is monitored at the VANA pin. Nominal level can be selected as 3.3 V or 5 V with the VANA_THRESHOLD bit. Overvoltage and undervoltage detection levels are selected with VANA_WINDOW as (nominal). VANA_THRESHOLD and VANA_WINDOW are set in the PGOOD_LEVEL_2 register.
VMON1 and VMON2 inputs can be used for monitoring external rails in the system. VMONx settings are defined in the PGOOD_LEVEL_1 and PGOOD_LEVEL_2 registers. Nominal value for the input level of VMONx is selected with VMONx_THRESHOLD, between 0.65 V to 1.8 V. Higher voltage levels or levels not directly supported can be monitored using an external resistor divider. In this case VMONx_THRESHOLD must be set as 0.65 V to have a high-impedance input, and the resistor divider must scale the monitored level down to 0.65 V at the VMONx pin. Overvoltage and undervoltage detection levels are selected with VMONx_WINDOW as ± 2%, ± 3%, ± 4% or ± 6%.
See Section 6 for more details on the accuracy of the monitoring windows and deglitch filtering.