cs5371 Cirrus Logic, Inc., cs5371 Datasheet - Page 15

• Manufacturer Part Number: cs5371
• Description: Low-power, High-performance ?? Modulators
• Manufacturer: Cirrus Logic, Inc.

9.3.
The VA- pin is tied to the CS5371/72 substrate and
should always be connected to the most negative
supply voltage to ensure SCR latch-up does not
occur. In general, latch-up may occur when any
pin voltage (including the analog inputs) is 0.7V or
more below VA-, or 7.6V or more above VA-.
Analog inputs INR+/- and INF+/- should be voltage
limited to ensure signals don’t exceed the (VA-)-
0.7V or (VA+)+7.6V requirement. Either the inputs
should be clamped to the VA+ and VA- rails using
reversed biased Schottky diodes (BAT85 or simi-
lar), or the current into the analog inputs should be
limited to less than 10mA. By current limiting the
analog inputs, the internal ESD diodes on the ana-
log input pads will clamp the input signal to the
proper level. Input currents greater than 10mA will
overdrive the internal diodes, so external compo-
nents are required.
When using dual analog power supplies, it is rec-
ommended to connect the VA- power supply pin to
system ground (DGND) using a reversed biased
Schottky diode. This configuration clamps the VA-
DS255F3
SCR Latch-up Considerations
voltage a maximum of 0.3V above ground to en-
sure SCR latch-up does not occur during power
up. If the VA+ power supply ramps before the VA-
supply, the VA- voltage could be pulled above
ground through the CS5371/72. If the VA- supply
is unintentionally pulled 0.7 V above the DGND
pin, SCR latch-up can occur.
9.4.
Many measurement systems are battery powered
and utilize DC-DC converters to generate the nec-
essary supply voltages for the system. To mini-
mize the effects of interference, it is desirable to
operate the DC-DC converter at a frequency which
is rejected by the digital filter.
9.5.
Power supply rejection of the CS5371/72 modula-
tors is frequency dependent. The digital filter re-
jects power supply noise for frequencies above the
filter corner frequency at 130 dB or greater. For
frequencies between DC and the digital filter cor-
ner frequency, power supply rejection is nearly
constant at 90 dB.
DC-DC Converter Considerations
Power Supply Rejection
CS5371 CS5372
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