ZHCSPB0 april 2023 LM5171-Q1
ADVANCE INFORMATION
When the monitors are set to monitor the inductor dc current, which is the input current in the boost mode, or the load current in the buck mode, the monitor current source is determined by Equation 6 and Equation 7:
Where
The 50 µA DC offset current is introduced to raise the no-load signal above the possible ground noise floor. Because the monitor signal is in the form of current, an accurate reading can be obtained across a termination resistor even if the resistor is located far from the LM5171-Q1 but close to the MCU, thus rejecting potential ground differences between the LM5171-Q1 and the MCU. Figure 7-9 shows a typical channel current monitor through a 20-KΩ termination resistor and a 10-nF to 100-nF ceramic capacitor in parallel. The RC network converts the current monitor signal into a DC voltage proportional to the channel DC current. For example, when the current sense voltage DC component is 50 mVdc, namely VCS_dc = 50 mV, the termination RC network produces a DC voltage of 3 V. Note that the maximum active operating voltage of the IMON pin is 3 V.
When the monitors are set to monitor the output DC current, which is the channel load current flowing out of the LV-port in the buck mode, or flowing out of the HV-port in the boost mode, the monitor current source is determined by Equation 8 through Equation 11:
Where
Obviously, the buck mode channel load current is the same as shown in Figure 7-5. However, the boost load current can be shown as in Figure 7-6.