AMC1305L25 Datasheet, PDF (21/39 Pages) Texas Instruments – AMC1305x High-Precision, Reinforced Isolated Delta-Sigma Modulators

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AMC1305L25, AMC1305M05, AMC1305M25
SBAS654C – JUNE 2014 – REVISED DECEMBER 2014
9.4 Device Functional Modes
9.4.1 Fail-Safe Output
In the case of a missing high-side supply voltage (AVDD), the output of a ΔΣ modulator is not defined and could
cause a system malfunction. In systems with high safety requirements, this behavior is not acceptable.
Therefore, the AMC1305 implements a fail-safe output function that ensures the device maintains its output level
in case of a missing AVDD, as shown in Figure 48.
CLKIN
AVDD
AVDD GOOD
AVDD FAIL
DOUT
Case 1: DOUT = Z1[ÁZvI(]o
DOUT
Case 2: DOUT = Z0[ÁZvI(]o
Figure 48. Fail-Safe Output of the AMC1305
9.4.2 Output Behavior in Case of Full-Scale Input
If a full-scale input signal is applied to the AMC1305 (that is, V_IN ≥ V_Clipping), the device generates a single one or
zero every 128 bits at DOUT, depending on the actual polarity of the signal being sensed, as shown in Figure 49.
In this way, differentiating between a missing AVDD and a full-scale input signal is possible on the system level.
CLKIN
DOUT
DOUT
...
...
VIN ^312.5 mV (AMC1305M05: 61.5 mV)
...
...
...
...
VIN _312.5 mV (AMC1305M05: 61.5 mV)
127 CLKIN cycles
127 CLKIN cycles
Figure 49. Overrange Output of the AMC1305
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