BCM4325
Preliminary Data Sheet
6/30/09
POWER SUPPLY TOPOLOGY
At least seven different power supply topologies can be supported by the voltage regulators available on the BCM4325.
Figure 5 shows one example of a power topology for an application with Bluetooth Class 1 PA, FM and WLAN supplied by
a variable battery voltage (Vbatt).
To achieve maximum performance from the integrated WLAN Power Amplifiers (PAs), the VDDPA power supply voltages
must remain within the recommended operating voltage range. If the supply voltage to the PA deviates outside this range,
the linearity of the PA will be degraded, resulting in lower throughput and shorter range. To avoid this condition, the buck-
boost regulator can be used to provide a constant 3.3V supply to the PA over the full range of the Vbatt voltage variation.
The trade-off is the additional components required for the buck-boost regulator versus the impaired performance if it is not
used.
Complete details of all seven power supply topologies are provided in the BCM4325 Power Supply Topologies application
note (document number 4325-AN60X-R), available on docSAFE.
VDDIO, VDDIO_SD
VDDIO = 1.8V – 3.3V
CLD0
Digital Logic and
Noise Insensitive
Blocks
1.5V
1.25V
1.5V Input
1.25V Output
200 mA
CBUCK
2.3V – 5.5V Input
1.5V Output
300 mA
LNLD01
1.5V Input
1.25V Output
130 mA
Vbatt = 2.3V – 5.5V
1.25V
1.25V
Noise Sensitive
Blocks (Radios, AFE,
LNA, Block etc.)
LNLD02
1.5V Input
1.25V Output
80 mA
VDD_FM
2.5V
3.3V
Bluetooth PA
VDD_BTTF
VDD_BTPA = 2.5V
Vbatt = 2.3V – 5.5V
BBOOST
2.3V – 5.5V Input
3.3V Output
300 mA
WLAN PA
VDDIO_RF
2.5V
Internal LDO
sr_avdd2p5
OTP
Figure 5: Power Topology Example
Broadcom Corporation
Page 4
Power Supply Topology
Document 4325-DS04-R
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