AMIS-492X0 Datasheet, PDF (13/22 Pages) ON Semiconductor – Fieldbus MAU

AMIS-492x0
Low Voltage Detectors
VDD
0.9*VREF
SHSETIN
VCC2
C3
R1
N_PFail1
4
C1
VDD
0.9*VREF
SRSETIN
VCC2
C4
N_PFail2
R2
5
C2
Figure 6: Low Voltage Detectors
If you do not use one of the regulators, the corresponding alarm signal can potentially be used to monitor another signal. For example,
if the series regulator is not used, SRAO should be left open, SRTR tied to VCC, VO grounded and SRSET left open. Then SRSETIN
can be the input for monitoring another voltage signal with N_PFAIL2.
4.2.4. Voltage Reference
The voltage reference circuitry generates two voltage signals, VREF and VMID. VREF comes from a bandgap circuit and is used as
the reference voltage for all circuits in the AMIS-492x0 Fieldbus MAU. The typical value for VREF is 1.185V. See Figure 7.
An operational amplifier is regulating VMID to provide a bias (common) level for the AC signals. Its typical voltage is 2V. A capacitor
larger than 0.01μF is necessary on VMID to remove high-frequency ripple.
Figure 7: Bandgap and VMID Voltage Reference
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