The baseband codec is a complete low power, two channel,
input/output port with signal conditioning. The transmit path
consists of an on-chip burst store, a GMSK modulator and two
high speed DACs with output reconstruction filters. The receive
path consists of two 15 bit Sigma Delta A/D converters which
include high performance digital filters for RF-channel selec-
tion.
The auxiliary section of the VBC consists of D/A converters for
Automatic Frequency Control (AFC), Automatic Gain Control
(AGC) and control of the transmit-burst envelope (RAMP).
Additionally, the VBC provides an auxiliary A/D converter
which can be used to monitor four analog signals.
Various power down options as well as the low supply voltage
allow the design of mobile radios having minimal power con-
sumption.
ORDERING GUIDE
Model
AD6421AST
Temperature Range
-40°C to +85°C
Package
64-Lead TQFP
GENERAL DESCRIPTION
The AD6421 is a monolithic Voiceband Baseband Codec
(VBC) that combines on a single chip all A/D and D/A convert-
ers that are necessary to build a complete GSM, DCS1800 or
PCS1900 mobile radio. It contains complete codecs for voice-
band and baseband signals as well as D/A converters to control
the radio subsystem and an auxiliary A/D converter for moni-
toring purposes.
The voiceband codec is a complete analog front-end which can
interface directly with a microphone and speaker. For interfac-
ing with external car-kits, separate input and output channels
are provided. Input and output gains are user programmable for
maximum flexibility.
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent
rights of Analog Devices.
REV. 0
-1-
AD6421
TDI TDO TMS TCK
AVDD DVDD AGND DGND
JTAG INTERFACE
8-BIT
MAIN AFC-DAC
ASDI
ASDIFS
ASCLK
ASDO
ASDOFS
AUXILIARY
SERIAL
PORT
32 x 10-BIT
RAMP- RAM
10-BIT
RAMP-DAC
INTERPOLATOR
10-BIT
SUB AFC-DAC
10-BIT AUX-ADC
ADC1
ADC2
ADC3
ADC4
AFC
RAMP
MCLK
RESET
10-BIT
AGC-DAC
BREF
AGC
TXON
RXON
CONTROL
REGISTER
FIR
FILTER
BASEBAND
SERIAL
PORT
BREFOUT
BREFCAP
BSDI
BSDIFS
BSCLK
BSDO
BSDOFS
I RECEIVE
ADC
IRXP
IRXN
QRXP
QRXN
ITXP
FILTER
ITXN
QTXP
FILTER
QTXN
VOUTNORP
VOUTNORN
FIR
FILTER
Q RECEIVE
ADC
I TRANSMIT
DAC
BURST
STORE
GMSK
Modulator
Q TRANSMIT
DAC
MODE
VSCLK
VSDI
VSDO
VSFS
VOICEBAND
SERIAL
PORT
FILTER
DAC
FILTER
PGA
VOUTAUXP
VOUTAUXN
BUZZER
VINNORP
VINNORN
FILTER
ADC
PGA
VINAUXP
VINAUXN
VREF
VREFCAP
VREFOUT
Figure 1. Detailed Block Diagram
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent
rights of Analog Devices.
REV. 0
-2-
AD6421
Table of Contents
GENERAL DESCRIPTION ............................................ 1
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent
rights of Analog Devices.
REV. 0
-3-
AD6421
PIN FUNCTIONALITY
Pin Group Name
Control
MCLK
TXON
RXON
MODE
RESET
Baseband Serial Port
BSDI
BSDIFS
BSCLK
BSDO
BSDOFS
Auxiliary Serial Port
ASDI
ASDIFS
ASCLK
ASDO
ASDOFS
Voiceband Serial Port
VSDI
VSCLK
VSDO
VSFS
Analog Baseband Interface
BREFCAP
BREFOUT
IRXP, IRXN
QRXP, QRXN
ITXP, ITXN
QTXP, QTXN
Pins
5
1
1
1
1
1
5
1
1
1
1
1
5
1
1
1
1
1
4
1
1
1
1
10
1
1
2
2
2
2
O
I/O
I
I
O
O
Baseband reference voltage output
Buffered baseband reference output / external bias voltage input
Differential analog input for in-phase receive signal
Differential analog input for quadrature receive signal
Differential analog output for in-phase receive signal
Differential analog output for quadrature receive signal
I
O
O
O
Voiceband serial port data input
Voiceband serial port clock output
Voiceband serial port data output. Tri-state when inactive.
Voiceband serial port framing signal output
I
I
I
O
I
Auxiliary serial port data input
Auxiliary serial port input-data framing signal input (level sensitive, active low)
Auxiliary serial port clock input
Auxiliary serial port data output. Tri-state when inactive.
Auxiliary serial port output-data framing signal input (level sensitive, active low)
I
I
O
O
O
Baseband serial port data input
Baseband serial port input-data framing signal input
Baseband serial port clock output
Baseband serial port data output.
Baseband serial port output-data framing signal
I
I
I
I
I
Master clock input
Baseband transmit section power-on input. When powering up/down is controlled
by the bit TXON in BCRA, the pin TXON should be tied low.
Baseband receive section power-on input. When powering up/down is controlled
by the bit RXON in the BCRA, the pin RXON should be tied low.
Proprietary Test Mode input. Should be tied low for normal operation
Active low reset signal input
I/O
Function
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent
rights of Analog Devices.
REV. 0
-4-
AD6421
Pin Group Name
Analog Auxiliary Interface
ADC1
ADC2
ADC3
ADC4
AFC
RAMP
AGC
Analog Voiceband Interface
VREFCAP
VREFOUT
VOUTNORP, VOUTNORN
VOUTAUXP, VOUTAUXN
VINNORP, VINNORN
VINAUXP, VINAUXN
BUZZER
JTAG Interface
TDI
TDO
TMS
TCK
Power Supplies
AVDD1
AVDD3
AVDD4
DVDD2, DVDD3
DVDD4
AGND1
AGND2
AGND3
AGND4
DGND2, DGND3
DGND4
Pins
7
1
1
1
1
1
1
1
11
1
1
2
2
2
2
1
4
1
1
1
1
13
1
1
1
2
1
1
1
1
1
2
1
Baseband Analog Power Supply
Voiceband Analog Power Supply
Auxiliary Analog Power Supply
Baseband / Auxiliary Digital Power Supply
Voiceband Digital Power Supply
Baseband Analog Ground
Analog Substrate
Voiceband Analog Ground
Auxiliary Analog Ground
Baseband / Auxiliary Digital Ground
Voiceband Digital Ground
I
O
I
I
Test data input
Test data output
Test mode select
Test clock
O
O
O
O
I
I
O
Voiceband reference voltage output
Buffered voiceband reference output
Differential voiceband normal output
Differential voiceband auxiliary output
Differential voiceband normal input
Differential voiceband auxiliary input
Buzzer output
I
I
I
I
O
O
O
Auxiliary A/D Converter Input 1
Auxiliary A/D Converter Input 2
Auxiliary A/D Converter Input 3
Auxiliary A/D Converter Input 4
Automatic Frequency Control signal output
Power Ramping Control signal output
Automatic Gain Control signal output
I/O
Function
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent
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