Cirrus Logic CRD5376 - Manual (Page 29)

CRD5376
DS612RD2 29
2.4.1 Analog Voltage Regulators
Linear voltage regulators create the positive and negative analog power supply voltages to the analog
components on CRD5376. These regulate the +3.3 V and -3.3 V power supply inputs to create the +2.5 V
and -2.5 V analog power supplies.
The +2.5 V and -2.5 V power supplies to the analog components on CRD5376 include reverse biased
Schottkey diodes to ground to protect against reverse voltages that could latch-up the CMOS analog com-
ponents. Also included on +2.5 V and -2.5 V are several 100 uF bulk capacitors for bypassing and to help
settle transients plus individual 0.1 uF bypass capacitors local to the power supply pins of each device.
2.5 PCB Layout
2.5.1 Layer Stack
CRD5376 layer 1 is dedicated for analog and digital routing. Critical analog signal routes for channels 1
and 2 are on this layer. Some digital routes for the digital filter are also included on this layer away from
the analog signal routes.
CRD5376 layer 2 is a solid ground plane without splits or routing. A solid ground plane provides the best
return path for bypassed noise to leave the system. No separate analog ground is required since analog
signals on CRD5376 are differentially routed.
CRD5376 layer 3 is dedicated for power supply routing. Each power supply net includes at least 100 µF
bulk capacitance as a charge well for settling transient currents.
CRD5376 layer 4 is dedicated as a digital routing layer with ground fill.
Specification Value
Positive Analog Power Supply
+2.5 V
Low Noise Micropower Regulator - Linear Tech LT1962ES8-2.5
Surface Mount Package Type MSOP-8
Load Regulation, -40 C to +85 C +/- 25 mV
Quiescent Current, Current @ 100 mA Load 30 µA, 2 mA
Output Voltage Noise, 10 Hz - 100 kHz 20 µV
RMS
Ripple Rejection, DC - 200 Hz > 60 dB
Specification Value
Negative Analog Supply
-2.5 V
Low Noise Micropower Regulator - Linear Tech LT1964ES5-BYP
Surface Mount Package Type SOT-23
Load Regulation, -40 C to +85 C +/- 30 mV
Quiescent Current, Current @ 100 mA Load 30 µA, 1.3 mA
Output Voltage Noise, 10 Hz - 100 kHz 20 µV
RMS
Ripple Rejection, DC - 200 Hz > 45 dB