LS1043 reset circuit:
The connection relationship is shown in the figure:
one PMIC,model is MC34VR500VAES.
one FPGA,model is xc7a15tcsg324.
one LS1043,model is LS1043AXE7QQB.
one power-on reset chip U3,model is ADM8611N293ACBZ-R7.
two input and gate U1, U2, model is 74LVC1G08.
one OCTAL BUFFERS/DRIVERS WITH 3-STATE OUTPUTS U4,model is SN74LVCH244APW.
The follow is a detailed description of the circuit:
The pin 1 of U1 is connected to the power-on status output of PMIC, it indicates that the PMIC is powered on. The pin 2 of U1 are disconnected during operation.
U3 is a 200ms power-on reset, the output of U1 and the output of U3 output a reset through U2 AND gate, which is connected to pin 2 and pin 4 of U4 as inputs. Pin 18 and pin 16 of U4 are output pins, respectively are connected to FPGA, LS1043. HRRESET_B_18 and PORESET_B_18, which are all pulled up to 1.8v.
Why is HRESET_B_18 only 700Mv? See the yellow waveform below, the blue waveform is PORESET_B_18, and the waveform is 1.8V, What is the reason?