The PLUTO baseband interface circuit is designed for use
in dual mode CDMA/AMPS digital cellular telephones. In the
telephone, Pluto provides the interface between the radio (RF
& IF) components and the baseband digital signal processor.
Pluto is part of a complete chipset solution for CDMA phones
entitled the Planet chipset.
The receive (RX) section converts the analog in-phase and
quadrature (I & Q) signals into equivalent digital signals whilst
the transmit (TX) circuits perform the complementary function
of translating digital baseband information into the analog
equivalent signals required for the modulator in the radio
circuits. VHF PLLS are also included for second RXLO and
TXIF generation.
PLUTO also contains a 4 channel general purpose ADC
which is included for such purposes as environmental and
signal strength monitoring.
FEATURES
■ Dual mode AMPS/CDMA compatible
■ Low Power/Low Voltage operation
■ Standard baseband I and Q interface
■ 4 Input Auxiliary ADC
■ Synthesisers
APPLICATIONS
■ Dual Mode CDMA/AMPs digital cellular
telephones
PLUTO
Advance Information
DS4722 - 1.8 July 1998
PIN 80
ABSOLUTE MAXIMUM RATINGS
Supply voltage-0.3 to 3.9V
Voltage applied to any other pin-0.3 to Vcc+0.3V
Operating junction temperature150°C
Storage temperature-55°C to 150°C
ESD (human body model)2kV
ORDERING INFORMATION
PLUTO/KG/GP1R
PIN 1 IDENT
PIN 1
Figure 1 Pin connections - top view
MP28
GP80
TCXO/4
CHIPx8
TCXO
/4
1025
512
19.68MHz
BUFFER
TXQ,TXQ-
FM_MOD
8-BIT
DAC
tx calibration and control
TXI,TXI-
8-BIT
DAC
PD_RX
TXIF
PD_TXRXIF
TX
SYNTH
SYNTH
RX
8-BIT
DAC
FC_I
RXIFMDATATXD<7:0>TXCLK
8-BIT
ADC
Figure 2 Block diagram
I+,I-BALQ+,Q-
8-BIT
DAC
6-BIT
ADC
rx calibration and control
RXQFMDATA
6-BIT
ADC
RXID<3:0>
FC_Q
8-BIT
DAC
8-BIT
ADC
RXQD<3:0>
ADC<3>
ADC<2>
ANALOG
MULTIPLEXER
ADCENA
ADCCLK
ADC<1>
8-BIT
ADC
ADC<0>
S<0>
S<1>
VDD
GND
SUB
FM/
SLEEP/
IDLE/
RESET/
SDATA
SCLOCK
SLATCH
ADCDATA
Page 2
PLUTO
PIN DESCRIPTION
NoPin NameTypeA/DDescription
1VDDPowerPower Supply
2RSETInputAnalogBias current setting resistor - 40kΩ to ground
3GNDGroundGround
4TX_IFInputAnalogTX VCO output
5IDLEBDigitalIdle mode control signal - active low - pulled low if left unconnected
6PD TXOutputTX synthesiser charge pump output
7FMBInputDigitalFM mode control signal - active low - pulled low if left unconnected
8PD_RXOutputAnalogRX synthesiser charge pump output
9SLEEPBInputDigitalSleep mode control signal - active low - pulled low if left unconnected
10RX_IFInputAnalogRX VCO output
11TX_LOCKOutputDigitalTX synthesiser lock detect open drain output - pulled high by ext. resistor
12RX_LOCKOutputDigitalRX synthesiser lock detect open drain output - pulled high by ext. resistor
13TCXO/4OutputDigitalTCXO divided by 4 output
14TXD<0>InputDigitalTransmit data bit 0 (lsb)
15TXD<1>InputDigitalTransmit data bit 1
16TXD<2>InputDigitalTransmit data bit 2
17TXD<3>InputDigitalTransmit data bit 3
18TXD<4>InputDigitalTransmit data bit 4
19TXD<5>InputDigitalTransmit data bit 5
20TXD<6>InputDigitalTransmit data bit 6
21TXD<7>InputDigitalTransmit data bit 7 (MSB)
22TXCLKInputDigitalComplimentary Transmit Clock (+ve)
23TXCLKBInputDigitalComplementary Transmit Clock (-ve)
24CHIPx8InputDigital9.8304MHz synthesiser output
25VDDPowerPower Supply
26TCXOInputAnalogTCXO 19.68MHz a.c. coupled sinewave input
27GNDGroundGround
28SUBGroundSubstrate-Ground
29RESETInputDigitalChip master reset - pulled high if not connected
30SDATAInputDigitalSerial Interface Data Input
31SCLKInputDigitalSerial Interface Clock Input
32SLATCHInputDigitalSerial Interfce Latch Input
33S<0>InputDigitalAux ADC mux channel select LSB
34n/c
35RXID<0>OutputDigitalI-Channel RX CDMA output LSB - low when inactive
36RXID<1>OutputDigitalI-Channel RX CDMA output bit 1 - low when inactive
37RXID<2>OutputDigitalI-Channel RX CDMA output bit 2 - low when inactive
38RXID<3>OutputDigitalI-Channel RX CDMA output bit 3 - low when inactive
39S<1>InputDigitalAux ADC mux channel select MSB
40n/c
41RXQD<0>OutputDigitalQ_Channel RX CDMA output LSB - low when inactive
42RXQD<1>OutputDigitalQ_Channel RX CDMA output bit 1 - low when inactive
43RXQD<2>OutputDigitalQ_Channel RX CDMA output bit 2 - low when inactive
44RXQD<3>OutputDigitalQ_Channel RX CDMA output bit 3 - low when inactive
45GNDGroundGround
46VDDPowerPower Supply
47RXFMSTBinputDigitalReceive data FM strobe - pulled low if not connected
48FMCLKInputDigitalReceive data FM clock - pulled low if not connected
49RXQFMDATAOutputDigitalQ-Channel RX FM data serial output - low when inactive
50RXIFMDATAOutputDigitalI-Channel RX FM data serial output -low when inactive
51ADCLKOutputDigitalAuxiliary ADC serial data clock. Low when inactive
52ADCDATAOutputDigitalAuxiliary ADC serial data output. Low when inactive
53ADCENAInputDigitalAuxiliary ADC enable - pull down if not used
54SUBGroundSubstrate - Ground
2
Page 3
PIN DESCRIPTION (continued)
NoPin NameTypeA/DDescription
55RXQPInputAnalogReceive Q Channel Input (+ve)
56RXQMInputAnalogReceive Q Channel Input (-ve)
57SUBGroundSubstrate - Ground
58RXIPInputAnalogReceive Q channel input (+ve)
59RXIMInputAnalogReceive Q channel Input (-ve)
60VDDPowerPower Supply
61GNDGroundGround
62VREF<0>Input/OutputAnalogCDMA Receive Circuit Voltage Reference De-Coupling
63AD<0>InputAnalogAUX ADC Input
64AD<1>InputAnalogAUX ADC Input
65AD<2>InputAnalogAUX ADC Input
66AD<3>InputAnalogAUX ADC Input
67VtestOutputDigitalRX Filter tuning tone output - pulled low when inactive
68EnTestOutputDigitalRX Filter tuning mode control output - pulled low when inactive
69FC_QOutputAnalogRX Filter Q channel FC control
70FC_IOutputAnalogRX Filter channel FC control
71BALOutputAnalogRX Filter Gain Balance Control
72VDDPowerPower Supply
73GNDGroundGround
74TXIPOutputAnalogTransmit Circuit channel Complementary Output (+ve)
75TXIMOutputAnalogTransmit Circuit I channel Complementary Output (-ve)
76SUBGroundSubstrate - Ground
77TXQPOutputAnalogTransmit Circuit Q channel Complementary Output (+ve)
78TXQMOutputAnalogTransmit Circuit Q channel Complementary Output (-ve)
79FMTXOutputAnalogTransmit Circuit FM output
80VREF<1>Input/OutputAnalogTransmit Circuit Voltage Reference De-coupling
PLUTO
FUNCTIONAL DESCRIPTION
Baseband TX interface circuit
The Pluto baseband transmit circuit acts as an interface
between the baseband signal processor and the RF/IF sections
in a CDMA/AMPS compatible mobile telephone.
The TX circuit has two modes of operation :
CDMA mode, transmit data that has previously been encoded
by the baseband digital signal processor is converted to
equivalent analog signals by matched digital-to-analog
converters, these signals are then filtered to remove the image
of the sample clock that would otherwise be present at the
output before being output to the I and Q modulator as
differential signals.
FM mode, transmit data is treated in much the same way as
in CDMA mode except that only one DAC is used and (because
of the much lower bandwidth of AMPS signals) a different
reconstruction filter is used before the analog fm signal is output
to the mixer as a single ended signal.
CDMA Transmit Signal Path
CDMA TX DACs
In CDMA mode two matched 8-bit DACs are used to
generate the in-phase and quadrature signals, the input
data for the DACs is obtained by multiplexing over an 8-bit
parallel input port (TXD<7:0>). The transmit data rate is
twice as fast as the differential transmit clock (TXCLK).
Incoming data that is valid during the rising edge of the
transmit clock is loaded into in In-Phase DAC & incoming
data that is valid on the falling edge of the transmit clock is
loaded into the Quadrature DAC - I and Q values must be
modified in the digital baseband chip to account for the halfcycle delay between them.
CDMA Analog Reconstruction Filters
The frequency spectrum at the output of the transmit
DACs contains unwanted frequency components.
Reconstruction filters are used to smooth the DAC output
signals, providing continuous time output signals at the I and
Q output pins thereby removing these undesirable signals.
The low pass filters used are 5th order Butterworth,
continuous time filters with a nominal cut-off frequency of 1.2
MHz. These filters are designed to have a linear phase
response in the pass band. On-chip reconstruction filters
minimise the phase and amplitude mismatch between I and
Q channels.
3
Page 4
PLUTO
CDMA TX Section Analog Interface
The ITx and QTx outputs can be d.c. or a.c. coupled to the
external circuits and will differentially drive a minimum
resistive load of 5 kΩ and a maximum capacitive load of 20 pF.
When the CDMA transmit path is in power-down mode the
positive outputs goes high and the negative output goes low.
FM Transmit Signal Path
FM TX DAC
In FM mode, the Q-Channel DAC is used to generate an
analog FM modulation signal from the data transmitted from
the digital baseband processor. In this mode, all other CDMA
TX circuits are powered down.
FM Mode Analog Reconstruction Filters
The frequency spectrum at the output of the transmit DAC
contains unwanted frequency components. A reconstruction
filter is used to smooth the DAC output signals.
Low-pass filters are used with a cut-off frequency of
approximately 13 kHz. These filters are 3rd order Butterworth
filters.
FM TX Section Analog Interface
The FMTX output can be d.c. or a.c. coupled to the radio
circuits and will drive a minimum resistive load of 5 kΩ and a
maximum capacitive load of 20 pF.
When the FM mode is in power-down the output is in high
impedance state.
CDMA Receive Signal Path
CDMA Receive ADC
In CDMA mode two high speed 4-bit ADCs are used to
digitise the incoming signals before subsequent transmission
to the baseband digital signal processor as two parallel 4 bit
words (RXI<3:0> and RXQ<3:0>). The sample rate of
9.8304MHz is generated via an on chip synthesiser that
requires no setting up or external components. On each falling
edge of the synthesised clock (CHIPx8) a new digital sample
is output on the digital bus.
CDMA Receive Calibration Circuit
On entering into CDMA mode from power down or from FM
mode the calibration circuits are activated. These circuits
measure the differences between the receive path gain in the
pass band and in the transition band of both I and Q filters. Via
a successive approximation process they tune the receive
filters cut-off frequency and amplitude matching using the 8 bit
DACs provided for this purpose (I_FC, Q_FC and BAL). Once
both filters (I and Q) have been calibrated in this way the DAC
outputs will not change until the chip is powered down or the
calibration circuit is re-activated in some other way.
FM Receive Signal Path
In FM mode two low speed 8-bit ADCs are used to digitise
the incoming signals before subsequent transmission to the
baseband digital signal processor as two serial 8-bit words
(FMRXI & FMRXQ). The sample rate is entirely determined by
the digital baseband processor (up-to the maximum allowed)
via the FMCLK input.
In FM mode the receive filters are assumed to track the
filters used in CDMA mode i.e. there is no separate tuning
mechanism.
SYNTHESISERS
The Synthesiser block comprises the input buffers, main
dividers, phase comparator, charge pump and lock detect
circuit for a TX and RX synthesiser. The loop filter components
and the VCOs are external to the device. A common reference
divider chain is also included together with bias and control
circuitry. All blocks apart from reference divider, bias and
control logic are duplicated exactly for RX and TX
synthesisers.
The receive intermediate frequency (RX_IF) is
programmable and the transmit intermediate frequency
(TX_IF) is fixed at 130.38MHz.
AUX ADC
The auxiliary converter section contains a single 8-bit
successive approximation analog to digital converter, with
serial output. In order to maximise the flexibility of Pluto, a 4
way analog multiplexer is provided, which enables the
converter to encode any one of four selectable channels. The
converter is intended for such applications as power supply
and temperature monitoring. When not in use, the converter is
powered down, and its outputs are held low.
4
Page 5
PLUTO
TIMING INFORMATION
ParameterValueUnitsConditions
MinTypMax
t1TXCLOCK PERIOD (CDMA TX)203.2nsCDMA TX Figure 3
t2TXCLOCK HIGH TIME (CDMA TX)101.6nsCDMA TX Figure 3
t3TXCLOCK LOW TIME (CDMA TX)101.6nsCDMA TX Figure 3
t4TXCLOCK PHASE Delay (CDMA TX)1.2nsCDMA TX Figure 3, FM TX Figure 4
t5TXCLOCK RISE TIME (CDMA TX)12nsCDMA TX Figure 3, FM TX Figure 4
t6TXCLOCK FALL TIME (CDMA TX)12nsCDMA TX Figure 3, FM TX Figure 4
t7TXD-TXCLOCK SETUP TIME20nsCDMA TX Figure 3, FM TX Figure 4
t8TXCLOCK-TXD HOLD TIME3nsCDMA TX Figure 3, FM TX Figure 4
The control modes for Pluto can be set via external pins or via a 3 wire serial interface. On initialising Pluto control is from
external pins but can then be set for programming from the serial interface by setting the appropriate bit in a serial input word.
The Rx second LO synthesiser is programmed via the serial interface: the Tx IF synthesiser is fixed and requires no programming.
Mode Control - External
The control modes are set by the pins SLEEPB, FMB and IDLEB as shown in the table below:
SLEEPBFMBIDLEBMode
(Pin 9)(Pin 7)(Pin 5)
0XXSleep Mode
100FM Receive only
101FM Receive and Transmit
110CDMA Receive only
111CDMA Receive and Transmit
Aux ADC Selection - External
The auxiliary analog to digital converters can be selected via pins S0 and S1 as shown in the table below:
S1S0ADC
(Pin 39)(Pin 33)selected
00ADC<0>
00ADC<1>
10ADC<2>
11ADC<3>
ADC selection can also be programmed to be via serial interface if required
Serial Interface
The 3 wire serial interface (SDATA, SCLK and SLATCH) is programmed using 24 bit words as shown below. Timing
Xunused
RXCRX Synth comparison frequency :0 = 30kHz, 1 = 5kHZ
RXDIV<13:0>RX Synth divider ratio
SOPExternal/ Serial mode selection: 0 = Ext, 1 = Serial
SLB, IDB, FMBSleep, Idle and FM mode control bits (serial mode)
TSTTest Mode Control - This is for test purposes only and should be set to 0
AD1, AD0Aux ADC select bits (serial mode)
MXSExternal / Serial Aux ADC select: 0 = Ext
CTBEnable Rx Calibration: 0 = calibration mode
If SOP is high mode control is via serial bits FMB, IDB and SLB, instead of external pins FMB, IDLEB and SLEEPB.
If MXS is high then ADC selection is via AD1, AD0 instead of S<1>, S<0>
8
Page 9
INITIALISATION
Transmit
On power-up or reset (RESETB) the Tx reconstruction
filters are tuned to give the specified cut-off frequency. This
calibration is internal and requires no external input. The
calibration time is 1ms.
Receive
On power-up or reset (RESETB) an autocalibration algorithm is started which can be used to tune the programmable
filters in Jupiter. (Jupiter is a programmable active filter designed for use in dual mode CDMA/AMPS system -further
details of which can be found in the Jupiter Datasheet). The
autocalibration is also initiated when Pluto is switched into
CDMA mode via FMB control.
PLUTO
When Pluto enters calibration mode the En Test (pin 68)
goes high. A test signal at 364kHz is then generated at the
Vtest output (pin 67). This signal is input to Jupiter which
provides a response which is digitised by the I and Q Rx ADCs.
An output DAC - BAL - (Pin 71) then tunes the Q channel to
match the I and Q channel amplitude via a successive approximation routine. The test signal is then switched to 728kHz
which is above the required cut off of the filter. DAC outputs,
FC_I and FC_Q are then adjusted to tune the I and Q filters to
the correct amplitude with reference to the in band test signal.
The filter cut off is tuned to 690kHz. Oversampling in the Rx
ADC's ensures sufficient accuracy for the calibration. This
calibration routine takes 26ms and after completion En Test
goes low and the test signal Vtest is disabled. Only the CDMA
filter is tuned, the matching within Jupiter ensures that the FM
(AMPS) filter performance meets specification.
0
-0.8
-4
Relative
Amplitude
(dB)
-5.8
CDMA TX FILTER RESPONSE
1k
Frequency (Hz)
630k1.25M
Figure 9 Baseband RX interface circuit
10M
-0.6
Relative
Amplitude
(dB)
-3.0
0
FM TX FILTER RESPONSE
10k
29k
Frequency (Hz)
100k
9
Page 10
PLUTO
RECOMMENDED OPERATING CONDITIONS
CharacteristicValueUnitsConditions
MinTypMax
Operating voltage range2.73.6V
Operating temperature range-40+85°C
Input high voltage, VIHVDD-0.8V
Input low voltage, VIL0.8V
Master clock amplitude800mV pk-pkAC coupled 19.68MHz sinusoidal
apply within the specified ambient temperature and supply voltage ranges unless otherwise stated.
= +2.7 to +3.6V. These characteristics are guaranteed by either production test or design. They
CC
CharacteristicValueUnitsConditions
MinTypMax
CDMA TX Interface
Resolution8Bits
Integral non-linearity0.5LSB
Differential non-linearity0.5LSB
Full scale output Voltage1.62.052.4VVpp differential
Output common mode Voltage1.11.21.3V
+Ve output Voltage in Power-down modeVdd-0.16 Vdd-0.1 Vdd-0.04V
-Ve output Voltage in Power-down mode0.040.10.16V
I,Q gain mismatch0.15dB
I,Q phase imbalance1degrees
Differential offsetTBDmV
PSRR50dBVDD to differential I & Q outputs,
apply within the specified ambient temperature and supply voltage ranges unless otherwise stated.
CharacteristicValueUnitsConditions
FM TX Interface
Resolution8Bits
Integral non linearity0.5LSB
Differential non linearity0.5LSB
Output Voltage range550mVpp
Output Voltage mid scale0VDifferential
PSRR50dBVdd to output, 100mV
Resolution4Bits
Full scale input voltage1V pk-pkMeasured differentially
Input common mode rangeVdd -1.4V
Input sample rate9.8304Ms/s
Input resistance (dc)20kΩ
Input capacitance1020pF
Integral non linearity0.15LSB
Differential non linearity0.175LSB
IRX and QRX gain matching0.25dB
= +2.7 to +3.6V. These characteristics are guaranteed by either production test or design. They
CC
MinTypMax
pk-pk at 100kHz
PLUTO
11
Page 12
PLUTO
ELECTRICAL CHARACTERISTICS (CDMA BASEBAND RX INTERFACE CIRCUIT) continued
T
= -30°C to +70°C, V
AMB
apply within the specified ambient temperature and supply voltage ranges unless otherwise stated.
CharacteristicValueUnitsConditions
FM RX Interface
Resolution8Bits
Full scale input voltage1V pk-pkMeasured differentially
Input dc levelVdd-1.4V
Input sample rate3050ks/s
Input resistance (dc)100kΩ
Input capacitance1020pF
Integral non linearity±1.5LSB
Differential non linearity±0.75LSB
AUXILIARY CONVERTER SECTION
Resolution8Bits
ADC full scale range2.5V
ADC zero scale range0.5V
Integral non linearity±1.25LSB
Differential non linearity±0.75LSB
Conversion time20ks/s
ADCCLK410kHz
= +2.7 to +3.6V. These characteristics are guaranteed by either production test or design. They
CC
MinTypMax
12
Page 13
ELECTRICAL CHARACTERISTICS (Continued)
T
= -30°C to +70°C, V
AMB
apply within the specified ambient temperature and supply voltage ranges unless otherwise stated.
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Copyright 1999 MITEL Corporation
All Rights Reserved
Printed in CANADA
TECHNICAL DOCUMENTATION - NOT FOR RESALE
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