Externally decouple the output of this regulator using a low ESR MLC capacitor of a minimum 2.2µF to the 3V3_USB
pin.
The output voltage is switched on when VCHG gets above 3.0V.
10.5
Low-voltage VDD_DIG Linear Regulator
The integrated low-voltage VDD_DIG linear regulator powers the digital circuits on CSR8640 BGA. Externally
decouple the output of this regulator using a low ESR MLC capacitor of 470nF.
10.6
Low-voltage VDD_AUX Linear Regulator
The integrated low-voltage VDD_AUX linear regulator is optionally available to provide a 1.35V auxiliary supply rail
when the 1.35V switch-mode regulator is not used. When using the integrated low-voltage VDD_AUX linear
regulator, externally decouple the output of this regulator using a low ESR MLC capacitor of a minimum 470nF to
the VDD_AUX pin.
10.7
Low-voltage VDD_ANA Linear Regulator
The integrated low-voltage VDD_ANA linear regulator is optionally available to power an optional 1.35V analogue
supply rail when the 1.35V switch-mode regulator is not used. When using the integrated low-voltage VDD_ANA
linear regulator, externally decouple the output of this regulator using a 2.2µF low ESR MLC capacitor to the
VDD_ANA pin.
10.8
Voltage Regulator Enable
When using the integrated regulators the voltage regulator enable pin, VREGENABLE, enables the CSR8640 BGA
and the following regulators:
■
1.8V switch-mode regulator
■
1.35V switch-mode regulator
■
Low-voltage VDD_DIG linear regulator
■
Low-voltage VDD_AUX linear regulator
The VREGENABLE pin is active high, with a weak pull-down.
CSR8640 BGA boots-up when the voltage regulator enable pin is pulled high, enabling the regulators. The firmware
then latches the regulators on, it is then permitted to release the voltage regulator enable pin.
The status of the VREGENABLE pin is available to firmware through an internal connection. VREGENABLE also
works as an input line.
10.9
External Regulators and Power Sequencing
CSR recommends that the integrated regulators supply the CSR8640 BGA and it is configured based on the
information in this data sheet.
If any of the supply rails for the CSR8640 BGA are supplied from an external regulator, then it should match or be
better than the internal regulator available on CSR8640 BGA. For more information see regulator characteristics in
Note:
The internal regulators described in Section 10.1 to Section 10.7 are not recommended for external circuitry
other than that shown in Section 12.
For information about power sequencing of external regulators to supply the CSR8640 BGA contact CSR.
10.10 Reset, RST#
CSR8640 BGA is reset from several sources:
Advance Information
This material is subject to CSR's non-disclosure agreement
© Cambridge Silicon Radio Limited 2011
Page 66 of 110
CS-209182-DSP1
CSR8640 BGA
Data Sheet