Cirrus Logic CDB5378 - Manual (Page 33)

CDB5378
DS639DB4 33
The VA+ and VA- power supplies to the analog components on CDB5378 can be jumpered to use regu-
lated bipolar power supplies (+2.5 V, -2.5 V) or unregulated direct connections (EXT_VA+, EXT_VA-).
When using direct connections to EXT_VA+ and EXT_VA-, extreme care must be taken not to exceed the
maximum specified power supply voltages of the analog components on CDB5378. It is recommended to
always use the regulated bipolar analog power supplies for optimal performance.
The VA+ and VA- power supply nets to the analog components on CDB5378 include reverse-biased
Schottkey diodes to ground to protect against reverse voltages that could latch-up the CMOS analog com-
ponents. Also included on VA+ and VA- are 100 uF bulk capacitors for bypassing and to help settle tran-
sients plus individual 0.1 uF bypass capacitors local to the analog power supply pins of each device.
2.4.2 Digital Voltage Regulators
Linear voltage regulators create the positive digital power supply voltages on CDB5378. Jumper options
select which external power supply input voltage, EXT_VD or EXT_VA+, is supplied to the digital voltage
regulators to create the VD and VCORE power supplies.
The VD and VCORE power supplies on CDB5378 can be jumpered to use regulated +3.3 V or +2.5 V
power supplies or an unregulated direct connection to EXT_VD. Extreme care must be taken when using
a direct connection to EXT_VD not to exceed the maximum specified power supply voltages of the digital
components on CDB5378.
Even though the Cirrus Logic components on CDB5378 will tolerate up to 5 V from the VD power supply,
other components are specified for +3.3 V operation only and so it is recommended to use only the reg-
ulated +3.3 V jumper setting for VD.
Specification Value
Negative Analog Supply, -2.5VA
-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
Specification Value
Positive Digital Power Supply
+2.5 V, +3.3 V
Low Noise Micropower Regulator - Linear Tech LT1763CS8
Surface Mount Package Type SO-8
Load Regulation, -40 C to +85 C +/- 25 mV
Quiescent Current, Current @ 100 mA Load 40
µA, 2 mA
Output Voltage Noise, 10 Hz - 100 kHz 20
µV
RMS
Ripple Rejection, DC - 200 Hz > 50 dB