TERIDIAN 73M1903C-IM/F

73M1903C
Modem Analog Front End
DATA SHEET
JANUARY 2008
DESCRIPTION
Features
The TERIDIAN 73M1903C Analog Front End
(AFE) IC includes fully differential hybrid driver
outputs, which connect to the telephone line
interface through a transformer-based DAA. The
receive pins are also fully differential for
maximum flexibility and performance. This
arrangement allows for the design of a high
performance hybrid circuit to improve signal to
noise performance under low receive level
conditions, and compatibility with any standard
transformer intended for PSTN communications
applications.
The device incorporates a programmable sample
rate circuit to support soft modem and DSP
based implementations of all speeds up to V.92
(56kbps). The sampling rates supported are from
7.2kHz to 16.0kHz by programming the prescaler NCO and the PLL NCO.
The TERIDIAN 73M1903C device incorporates a
digital host interface that is compatible with the
serial ports found on most commercially available
DSPs and processors and exchanges both
payload and control information with the host.
This interface can be configured as a single
master/slave mode or as a daisy chain mode that
allows the user to connect up to eight 73M1903C
devices to a single host for multi Analog Front
End applications, such as, central server
modems.
Costs saving features of the device include an
input reference frequency circuit, which accepts a
range of crystals from 4.9-27MHz. It also accepts
external reference clock values between 1MHz40MHz generated by the host processor. In most
applications, this eliminates the need for a
dedicated crystal oscillator and reduces the bill of
materials (BOM).
The 73M1903C also supports two analog loop
back and one digital loop back test modes.
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Two pairs of software selectable transmit
differential outputs for worldwide impedance
driver implementations.
Up to 56kbps (V.92) performance
Programmable sample rates (7.2-16.0kHz)
Reference clock range of 1-40MHz
Crystal frequency range of 4.9-27MHz
Master or slave mode operation and daisy
chain configurable synchronous serial Host
interface
Low power modes
Fully differential receiver and transmitter
Drivers for transformer interface
3.0V – 3.6V operation
5V tolerant I/O
Industrial temperature range (-40 to +85°C)
JATE compliant transmit spectrum
Package options: 32 pin QFN
Applications
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Central site server modems
Set Top Boxes
Personal Video Recorders (PVR)
Multifunction Peripherals (MFP)
Fax Machines
Internet Appliances
Game Consoles
Point of Sale Terminals
Automatic Teller Machines
Speaker Phones
Digital Answering Machines
RF Modems
VBG
(HYBRID)
TXAP1
TXAN1
TXAP2
TXAN2
RXAP
RXAN
GPIO
HOOK
Transmit
Drivers/
Filters
Analog
Sigma
Delta
Receiver
MUX/
Filters
DAC
DAA
controls
Clock
Ref.
SCLK
Control
Registers
SDIN
Serial
Port
SDOUT
FS
Control
Logic
FSD
Crystal
Page: 1 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Table of Contents
DESCRIPTION.............................................................................................................................................. 1
Features ........................................................................................................................................................ 1
Applications................................................................................................................................................... 1
SIGNAL DESCRIPTION ............................................................................................................................... 4
SERIAL INTERFACE .................................................................................................................................... 5
CONTROL REGISTER MAP ...................................................................................................................... 11
SYSTEM CONTROL REGISTERS............................................................................................................. 12
GPIO REGISTERS ..................................................................................................................................... 13
PLL CONFIGURATION REGISTERS......................................................................................................... 14
CLOCK GENERATION ............................................................................................................................... 17
ANALOG I/O ............................................................................................................................................... 20
MODEM TRANSMITTER............................................................................................................................ 21
MODEM RECEIVER ................................................................................................................................... 24
TEST MODES............................................................................................................................................. 28
POWER SAVING MODES.......................................................................................................................... 28
ELECTRICAL SPECIFICATIONS............................................................................................................... 29
ABSOLUTE MAXIMUM RATINGS.......................................................................................................... 29
RECOMMENDED OPERATING CONDITIONS...................................................................................... 29
DIGITAL SPECIFICATIONS ....................................................................................................................... 30
DC CHARACTERISTICS ........................................................................................................................ 30
AC TIMING .............................................................................................................................................. 31
ANALOG SPECIFICATIONS ...................................................................................................................... 32
DC SPECIFICATIONS ............................................................................................................................ 32
AC SPECIFICATIONS............................................................................................................................. 32
PERFORMANCE..................................................................................................................................... 33
PACKAGE OPTIONS.................................................................................................................................. 35
MECHANICAL DRAWINGS........................................................................................................................ 36
73M1903C DAA Resistor Calculation Guide........................................................................................... 37
APPENDIX B............................................................................................................................................... 40
Crystal Oscillator ..................................................................................................................................... 40
PLL .......................................................................................................................................................... 41
Examples of NCO settings ...................................................................................................................... 42
ORDERING INFORMATION....................................................................................................................... 46
Page: 2 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
List of Figures
Figure 1: SCLK and FS with SckMode=0.................................................................................................. 7
Figure 2: Control frame position vs. SPOS .............................................................................................. 7
Figure 3: Serial Port Timing Diagrams...................................................................................................... 8
Figure 4: 73M1903C Host connection in master and slave mode ................................................................ 9
Figure 5: 73M1903C Daisy chaining for master/slave mode and slave modes .................................... 9
Figure 6: Clock Generation ......................................................................................................................... 17
Figure 7: Analog block diagram .................................................................................................................. 20
Figure 8: Overall TX path frequency response at 8kHz sample rate.......................................................... 21
Figure 9: Frequency response of TX path for DC to 4kHz in band signal at 8kHz sample rate........ 22
Figure 10: Overall receiver frequency response at 8kHz sample rate................................................. 25
Figure 11: Rx passband response at 8kHz sample rate........................................................................ 26
Figure 12: RXD Spectrum of 1kHz tone .................................................................................................. 27
Figure 13: RXD Spectrum of 0.5kHz, 1kHz, 2kHz, 3kHz and 3.5kHz tones of Equal Amplitudes...... 27
Figure 14: Serial Port Data Timing .......................................................................................................... 31
Figure 15: Typical DAA block diagram........................................................................................................ 37
Figure 16: Single transmitter arrangement ................................................................................................. 38
Figure 17: Dual transmitter arrangement .................................................................................................... 39
Figure 18: NCO block diagram ................................................................................................................... 40
Figure 19: PLL Block Diagram .................................................................................................................... 41
Page: 3 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
PIN DESCRIPTION
The TERIDIAN 73M1903C modem Analog Front End (AFE) IC is available in a 32 pin QFN package. The
following table describes the function of each pin. There are three pairs of power supply pins, VPA
(analog), VPD (digital) and VPPLL (PLL). They should be separately decoupled from the supply source
in order to isolate digital noise from the analog circuits internal to the chip. VPPLL can be directly
connected to VPD. Failure to adequately isolate and decouple these supplies will compromise device
performance.
PIN NAME
TYPE
PIN #
DESCRIPTION
VND
GND
1, 22
Negative Digital Ground
VNA
GND
16
Negative Analog Ground
VPD
PWR
2, 25
Positive Digital Supply
VPA
PWR
9
Positive Analog Supply
VPPLL
PWR
20
Positive PLL Supply, shared with VPD
VNPLL
PWR
17
Negative PLL Ground
RST
I
26
Master reset. When this pin is a logic 0 all registers are reset to their
default states; Weak-pulled high-default. A low pulse longer than 100ns
is needed to reset the device. The device will be ready within 100us after
this pin goes to logic 1 state.
OSCIN
I
19
Crystal oscillator input. When providing an external clock source, drive
OSCIN.
OSCOUT
O
18
Crystal oscillator circuit output pin.
GPIO(0-7)
I/O
3, 4, 5, 6, 23 24,
30, 31
Software definable digital input/output pins.
RXAN
I
14
Receive analog negative input.
RXAP
I
15
Receive analog positive input.
TXAN1
O
10
Transmit analog negative output 1
TXAN2
O
11
Transmit analog negative output 2
TXAP1
O
12
Transmit analog positive output 1
TXAP2
O
13
Transmit analog positive output 2
SCLK
I/O
8
Serial interface clock. With master mode and SCLK continuous selected,
Freq = 256*Fs ( =2.4576MHz for Fs=9.6kHz). For slave mode, this pin
must be pulled down by a resistor (<4.7kΩ).
SDOUT
O
32
Serial data output (or input to the host).
SDIN
I
29
Serial data input (or output from the host)
FS
O
7
TYPE
I
27
Frame synchronization. (Active Low)
Type of frame sync. 0 = late (mode0); 1 = early (mode1). Weak-pulled
high – default
SckMode
I
28
FSD
O
21
Controls the SCLK behavior after FS. Open, weak-pulled high = SCLK
Continuous; tied low = 32 clocks per R/W cycle.
Delayed frame sync to support daisy chain mode with additional
73M1903C devices
Table 1: 32 QFN Pin Description
Page: 4 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
MODEM ANALOG FRONT END (MAFE) SERIAL INTERFACE
The MAFE (Modem Analog Front End) serial data port is a bi-directional port that can be supported by
most DSPs. The typical I2S (Inter-IC Sound, NXP semiconductor) bus can be easily converted into MAFE
compatible interface. The 73M1903C can be configured either as a master or a slave of the serial
interface. When the 73M1903C is configured as a master device, it generates a serial bit clock, Sclk,
from a system clock, Sysclk, which is normally an output from an on-chip PLL that can be programmed by
the user. In master mode, the serial bit clock is always derived by dividing the system clock by 18. The
Sclk rate, Fsclk, is related to the frame synchronization rate (sample rate), Fs, by the relationship Fsclk =
256 x Fs or Fs = Fsclk / 256 = Fsys / 18 / 256 = Fsys / 4608, where Fsys is the frequency of Sysclk. Fs is
also the rate at which both transmit and receive data bytes are sent (received) to (by) the Host.
Throughout this document two pairs of sample rate, Fs, and crystal frequency, Fxtal, will be often cited to
facilitate discussions. They are:
1. Fxtal1 = 27MHz, Fs1 = 7.2kHz
2. Fxtal2 = 18.432MHz, Fs2 = 8kHz.
3. Fxtal3 = 24.576MHz, Fs3 = 9.6kHz
Upon reset, until a switch to the PLL based clock, Pllclk, occurs, the system clock will be at the crystal
frequency, Fxtal, and therefore the serial bit clock will be sclk = Fsys/18 = Fxtal/18.
Examples:
1. If Fxtal1 = 27.000MHz, then sclk=1.500MHz and Fs=sclk/256 = 5.859375kHz.
2. If Fxtal2 = 18.432MHz, then sclk=1.024MHz and Fs=sclk/256 = 4.00kHz.
3. If Fxtal3 = 24.576MHz, then sclk=1.3653MHz and Fs=sclk/256 = 5.33kHz.
When 73M1903C is programmed through the serial port to a desired Fs and the PLL has settled out, the
system clock will transition to the PLL-based clock in a glitch-less manner.
Examples:
1. If Fs1 = 7.2kHz, Fsys = 4608 * Fs = 33.1776MHz and sclk = Fsys / 18 = 1.8432MHz.
2. If Fs2 = 8.0kHz, Fsys = 4608 * Fs = 36.8640MHz and sclk = Fsys / 18 = 2.048MHz.
3. If Fs3 = 9.6kHz, Fsys = 4608 * Fs = 44.2368MHz and sclk = Fsys / 18 = 2.4576MHz.
This transition is entirely controlled by the host. Upon reset or power down of PLL and/or analog front
end, the chip will automatically run off the crystal until the host forces the transition by setting Frcvco bit
(Bit 7 in Register0E). The transition should be forced on or after the second frame synch period following
the write to a designated PLL programming registers (Register08 to Register0D).
When reprogramming the PLL the host should first transition the system clock to the crystal before
reprogramming the PLL so that any transients associated with it will not adversely impact the serial port
communication.
Power saving is accomplished by disabling the analog front end by clearing ENFE bit (bit 7 Register00).
During the normal operation, a data frame sync signal (FS) is generated by the 73M1903C at the rate of
Fs. For every data FS there are 16 bits transmitted and 16 bits received. The frame synchronization (FS)
signal is pin programmable for type. FS can either be early or late determined by the state of the TYPE
input pin. When Type pin is left open, an early FS is generated in the bit clock prior to the first data bit
transmitted or received. When held low, a late FS operates as a chip select; the FS signal is active for all
bits that are transmitted or received. The TYPE input pin is sampled when the reset pin is active and
ignored at all other times. The final state of the TYPE pin as the reset pin is de-asserted determines the
frame synchronization mode used.
Page: 5 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
SERIAL DATA AND CONTROL
The bits transmitted on the SDOUT pin are defined as follows:
bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
RX15 RX14 RX13 RX12 RX11 RX10 RX9 RX8 RX7 RX6 RX5 RX4 RX3 RX2 RX1 RX0
If the HC bit (Bit 0 of Register01) is set to zero, the 16 bits that are received on the SDIN are defined as
follows:
bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4
TX15 TX14 TX13 TX12 TX11 TX10 TX9 TX8 TX7 TX6 TX5 TX4
In this case LSB(TX0) in a transmit bit stream is forced to 0 automatically.
bit3
TX3
bit2
TX2
bit1
TX1
bit0
CTL
If the Hardware Control bit (Bit 0 of Register 01) is set to one, the 16 bits that are received on the SDIN
input are defined as follows:
bit15 bit14 bit13 bit12 bit11 bit10 bit9
TX15 TX14 TX13 TX12 TX11 TX10 TX9
bit8
TX8
bit7
TX7
bit6
TX6
bit5
TX5
bit4
TX4
bit3
TX3
bit2
TX2
bit1
TX1
bit0
TX0
Bit 15 is transmitted/received first. Bits RX15:0 are the receive code word. Bits TX15:0 are the transmit
code word. If the hardware control bit is set to one, a control frame is initiated between every pair of data
frames. If the hardware control bit is set to zero, CTL is used by software to request a control frame. If
CTL is high, a control frame will be initiated before the next data frame. A control frame allows the
controller to read or write status and control to the 73M1903C.
The control word received on the SDIN pin is defined as follows:
bit15 bit14 bit13 bit12 bit11 bit10
R/W A6
A5
A4
A3
A2
bit9
A1
bit8
A0
bit7
D7
bit6
D6
bit5
D5
bit4
D4
bit3
D3
bit2
D2
bit1
D1
bit0
D0
bit4
D4
bit3
D3
bit2
D2
bit1
D1
bit0
D0
The control word transmitted on the SDOUT pin is defined as follows:
bit15 bit14 bit13 bit12 bit11 bit10
0
0
0
0
0
0
bit9
0
bit8
0
bit7
D7
bit6
D6
bit5
D5
If the R/W bit (Bit15 of control word) is set to a 0, the data byte transmitted on the SDOUT pin is all zeros
and the data received on the SDIN pin is written to the register pointed to by the received address bits;
A6-A0. If the R/W bit is set to a 1, there is no write to any register and the data byte transmitted on the
SDOUT pin is the data contained in the register pointed to by address bits A6-A0. Only one control frame
can occur between any two data frames.
Writes to unimplemented registers are ignored. Reading an unimplemented register returns an unknown
value. The position of a control data frame is controlled by the SPOS; bit 1 of register 01h. If SPOS is
set to a 0 the control frames occur mid way between data frames, i.e., the time between data frames is
equal. If SPOS is set to a 1, the control frame is ¼ of the way between consecutive data frames, i.e., the
control frame is closer to the first data frame. This is illustrated in Figure 2.
The TERIDIAN 73M1903C modem AFE IC includes a feature that shuts off the serial clock (SCLK) after
32 cycles of SCLK following the frame synch (figure 1). The SckMode pin controls this mode. If this pin
is left open the clock will run continuously. If SckMode is set low, the clock will be gated on for 32 clocks
Page: 6 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
for each FS. The SDOUT and FS pins change values following a rising edge of SCLK. The SDIN pin is
sampled on the falling edge of SCLK. Figure 3 shows the timing diagrams for the serial port.
32 Cycles of SCLK
SCLK
FS
(early mode)
SCLK Relative to early FS
32 Cycles of SCLK
SCLK
FS
(late mode)
SCLK Relative to late FS
Figure 1: SCLK and FS with SckMode=0
DATA FRAMES
SPOS = 0
SPOS = 1
CONTROL FRAMES
Figure 2: Control frame position vs. SPOS
Page: 7 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
SCLK
FS
SDIN
TX15
TX14
TX13
TX12
TX11
TX10
TX9
TX8
TX7
TX6
TX5
TX4
TX3
TX2
TX1
CTL
SDOUT
RX15
RX14
RX13
RX12
RX11
RX10
RX9
RX8
RX7
RX6
RX5
RX4
RX3
RX2
RX1
RX0
Data Frame with earlyl Frame Sync
SCLK
FS
SDIN
TX15
TX14
TX13
TX12
TX11
TX10
TX9
TX8
TX7
TX6
TX5
TX4
TX3
TX2
TX1
CTL
SDOUT
RX15
RX14
RX13
RX12
RX11
RX10
RX9
RX8
RX7
RX6
RX5
RX4
RX3
RX2
RX1
RX0
Data Frame with late Frame Sync
SCLK
FS
SDIN
R/W
A6
A5
A4
A3
A2
A1
A0
DI7
DI6
DI5
DI4
DI3
DI2
DI1
DI0
SDOUT
zero
zero
zero
zero
zero
zero
zero
zero
DO7
DO6
DO5
DO4
DO3
DO2
DO1
DO0
Control Frame with early Frame Sync
SCLK
FS
SDIN
R/W
A6
A5
A4
A3
A2
A1
A0
DI7
DI6
DI5
DI4
DI3
DI2
DI1
DI0
SDOUT
zero
zero
zero
zero
zero
zero
zero
zero
DO7
DO6
DO5
DO4
DO3
DO2
DO1
DO0
Control Frame with late Frame Sync
Sample Rate
SCLK
FS
1
16
128
144
256
1
SDIN
TX
TX
TX
TX
TX
1
R
A
A
A
DI
DI
DI
TX
TX
TX
TX
TX
0
SDOUT
RX
RX
RX
RX
RX
RX
0
0
0
0
DO
DO
DO
RX
RX
RX
RX
RX
RX
Data Frame
Control Frame
Data Frame
Relation Between the Data and Control Frames
(Master Mode, continuous clock, default SPOS)
Figure 3: Serial Port Timing Diagrams
Page: 8 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
SLAVE MODE AND DAISY CHAIN
If the SCLK pin is externally pulled down to ground by a <4.7KΩ resistor, the 79M1903C device is in the
slave mode, after reset. In this mode of operation the serial clock (SCLK) and FS are inputs to 79M1903C
provided by the Master device. The serial clock input must be connected to OSCIN pin while SCLK pin of
73M1903C is unconnected, except for the resistor connected to ground (see Figures 4 and 5). The
73M1903C PLL must be programmed to multiply the serial clock frequency by an appropriate factor in
order to obtain Fsys. Therefore the serial clock has to be continuous and without low frequency jitter (the
high frequency jitter is rejected by the 79M1903C PLL). The SckMode pin is not used since the Master
device provides FS and serial clock.
MCLK
73M1903C
OSCIN
SDOUT
HOST
(Slave)
73M1903C
(Master)
SCLK
SDIN
SDOUT
HOST
SDOUT
SDIN
FS
FS
SckMode
SCLK
SCLK
TYPE
"1/0"
SDIN
(Master)
FS
OSCIN
SDIN
SDOUT
FS
"1/0"
(Slave)
SCLK
"x"
SckMode
"x"
TYPE
"x" : don't care
73M1903C Master Mode
73M1903C Slave Mode
Figure 4: 73M1903C Host connection in master and slave mode
MCLK
SDOUT
HOST
(Slave)
SDIN
FS
SCLK
73M 1903C
SCLK
OSCIN (Master)
SDOUT
SDIN
SDOUT
HOST
FS
SCLK
SckMode
FSBD
TYPE
"1/0"
(Master)
SDIN
FS
"1/0"
SDIN
SDOUT
FS
SckMode
SCLK
TYPE
"x" : don't care
(Slave)
SDIN
SDOUT
SDOUT
SCLK
SckMode
TYPE
"x"
73M 1903C
OSCIN
(Slave)
SDIN
FS
"x"
FSBD
73M 1903C
OSCIN
73M 1903C
OSCIN (Slave)
"x"
FS
"x"
Daisy chain for M aster/Slave mode
SCLK
SckMode
TYPE
"x"
"x"
Daisy chain for Slave mode
Figure 5: 73M1903C Daisy chaining for master/slave mode and slave modes
In order to daisy chain two or more 73M1903C devices, the master must be programmed into hardware
controlled control frame mode by setting the HC bit (bit 0 in Register01) to “1”, then set FSDEn (bit 3 in
Register06), and then set CkoutEn bit (bit 3 in Register01) to allow the FSD to come through. The first
Page: 9 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
frame after enabling FSD must be Data. For the two daisy chained devices, the data/control frames are
32 bits. The first 16 bits go to the first device; the next 16 bits go to the second device in the chain, as
timed by FSD of the first device. For four daisy-chained devices, the data/control frames are 64 bits. The
first 16 bits go to the first device in the chain; the next 16 bits go to the second device in the chain as
started by FSD of the first device, etc. FSD is always ”Late Type” frame sync.
Up to eight 73M1903C devices may be daisy-chained if the control frame sync is placed at the middle of
the data frame sync interval. Four devices may be daisy-chained if the control frame sync is placed at the
1/4 of the data frame sync interval. In all cases involving slave and daisy chain operation, only hardware
controlled Control Frames can be supported. Software requested control frames are not allowed.
In slave mode the relationship of Fs and Fsclk is Fsclk/Fs, with a range of from 96 to 256 SCLKs per Fs.
Again, the host controls the relationship of FS to SCLK, with the condition that Fsclk>750kHz and
Fsys=4608*Fs. The 79M1903C PLL must be programmed to generate Fsys with those conditions. To
program the 73M1903C NCOs, OSCIN (Fsclk)=SCLK=Fref when Pdvsr=1 and Prst=0 in the calculations.
Fsys in the previous discussion is Fvco in the calculations which is equal to 4608*Fs. For example, two
typical cases are Fsclk=256*Fs and Fsclk=144*Fs.
For the case when Fsclk=256*Fs and Fs=8kHz, the 79M1903C PLL has to be set to
Fsys=4608*Fs=36.864MHz, and Sclk=256*8kHz=2.048MHz. Therefore Ndvsr=36.864/2.048=18 (12h)
and Nrst=0
For the case when Fsclk=144*Fs and d Fs=8kHz, the 79M1903C PLL has to be set to
Fsys=4608*Fs=36.864MHz and Sclk=144*8kHZ=1.152MHz. Therefore Ndvsr=36.864/1.152=32 (20h)
and Nrst=0
Page: 10 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
CONTROL REGISTER MAP
The following Table 2 shows the map of addressable registers in the 73M1903C. Each register and its
bits are described in detail in the following sections.
Register
Name
Address
Default
BIT 7
BIT 6
CTRL
00h
08h
ENFE
SELTX2
TEST
01h
00h
TMEN
DIGLB
ANALB
INTLB
CkoutEn
RXPULL
SPOS
HC
DATA
02h
FFh
GPIO7
GPIO 6
GPIO 5
GPIO 4
GPIO 3
GPIO 2
GPIO 1
GPIO 0
DIR
03h
FFh
DIR7
DIR6
DIR5
DIR4
DIR3
DIR2
DIR1
DIR0
Register04
04h
00h
Reserved
Register05
05h
00h
Reserved
REV
06h
60h
Register07
07h
00h
Reserved
PLL_PSEQ
08h
00h
Pseq(7:0)
PLL_RST
09h
0Ah
PLL_KVCO
0Ah
22h
PLL_DIV
0Bh
12h
PLL_SEQ
0Ch
00h
XTAL_BIAS
0Dh
C0h
BIT 5
BIT 4
TXBST(1:0)
Rev(3:0)
BIT 3
TXDIS
BIT 2
RXG(1:0)
FSDEn
Prst(2:0)
BIT 1
BIT 0
RXGAIN
Reserved
Pdvsr(4:0)
Ichp(3:0)
Reserved
-
Kvco(2:0)
Ndvsr(6:0)
Nseq(7:0)
Xtal(1:0)
Reserved
-
Nrst(2:0)
PLL_LOCK
0Eh
00H
Frcvco PwdnPll LockDet
Note: Register or bit names in bold underline denotes the READ ONLY bits and registers.
Register bits marked “-“ are not used. Writing any value to these bits won’t affect the operation.
Reserved are bits reserved for factory test purpose only. Do not attempt to write these locations to values
other than their default to prevent unexpected operation.
Register Bit notations used in this document are as follows.
- Registerxx: Register05 represents the register with Address 0x05
- BIT(s)NAME(MSB:LSB) ; Rev(3:0) represents 4 bits of Rev3, Rev2, Rev1 and Rev0.
-(RegisterAddress[BIT(s)]) ; (0X00[7]) represents Bit 7 of Register address 0x00, ENFE bit
(0X06[7:4]) represents Bit 7, Bit 6, Bit 5 and Bit4 of Register address 06, Rev(3:0).
Table 2: Register Map
Page: 11 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
SYSTEM CONTROL REGISTERS
Register00 (CTRL): Address 00h
Reset State 08h
BIT 7
BIT 6
ENFE
SelTX2
ENFE
SelTX2
TXBST1
TXBST0
TXDIS
RXG(1:0)
RXGAIN
BIT 5
TXBST
BIT 4
TXBST0
BIT 3
TXDIS
BIT 2
RXG1
BIT 1
RXG0
BIT 0
RXGAIN
(0X00[7]) Enable Front End.
1 = Enable the digital filters and analog front end.
0 = Disable the analog blocks shut off the clocks to the digital and analog receive/transmit
circuits.
(0X00[6]) Select Tx driver 2
1 = Selects Secondary transmitter (TXAP2 and TXAN2) if TXDIS=0
0 = Selects Primary transmitter (TXAP1 andTXAN1) if TXDIS=0
(0X00[5])
1 = Add a gain of 1.335dB (16.6%) to the transmitter; also the common mode voltage of the
transmit path is increased to 1.586V. This is intended for enhancing DTMF transmit power
only and should not be used in data mode.
0 = No gain is added
(0X00[4])
1 = A gain of 1.65dB(21%) is added to the transmitter
0 = The gain of the transmitter is nominal
(0X00[3])
1 = Tri-state the TXAP1,2 and TXAN1,2 pins, provides a bias of VBG into 80 kΩ for each
output pin
(0X00[2:1]) Rx Gain Selection
00 = 6 dB Receive Gain
01 = 9 dB
10 = 12 dB
11 = 0 dB
(0X00[0]) 20 dB RxGain Enable. This gain selection can be used for line snoop or Caller ID
detection.
1 = Increase the gain of the receiver by 20 dB.
0 = Normal operation
Register01 (TEST): Address 01h
Reset State 00h
BIT 7
BIT 6
TMEN
DIGLB
TMEN
DIGLB
ANALB
BIT 5
ANALB
BIT 4
INTLB
BIT 3
CkoutEn
BIT 2
RXPULL
BIT 1
SPOS
BIT 0
HC
(0X01[7]) Test Mode Enable.
0 = Normal operation
1 = Enable test modes.
(0X01[6]) Digital Loop back Enable
0 = Normal operation
1 = Tie the serial bit stream from the digital transmit filter output to the digital receive filter
input.
(0X01[5]) Analog Loop back Enable
0 = Normal operation
1 = Tie the analog output of the transmitter to the analog input of the receiver.
Page: 12 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
INTLB
CkoutEn
RXPULL
SPOS
HC
(0X01[4]) Internal Loop back Enable. (Remote Analog Loop back)
0 = Normal operation
1 = Tie the digital serial bit stream from the analog receiver output to the analog transmitter
input.
(0X01[3]) Clock Output Enable
1=
Enable the CLKOUT output; This bit must be set after the FSDEn bit is set to enable
daisy chain mode.
0=
CLKOUT tri-stated, for normal operation.
(0X01[2])
1=
Pulls DC Bias to RXAP/RXAN pins, thru 100Kohm each, to VREF, to be used in
testing Rx path.
0=
No DC Bias to RXAP/RXAN pins
(0X01[1])
1=
Control frames occur after one quarter of the time between data frames has elapsed.
0=
Control frames occur half way between data frames.
(0X01[0])
1=
Control frame generation is under hardware control, bit 0 of data frames on SDIN is bit
0 of the transmit word and control frames happen automatically after every data frame.
0=
Control frame generation is under software control, bit 0 of data frames on SDIN is a
control frame request bit and control frames happen only on request.
Register06 (REV): Address 06h
Reset State 60h
BIT 7
BIT 6
BIT 5
Rev(3:0)
Rev(3:0)
FSDEn
BIT 4
BIT 3
FSDEn
BIT 2
BIT 1
Reserved
BIT 0
(0X06[7:4]) Contain the revision ID of the TERIDIAN 73M1903C device. The rest of this
register is for chip development purposes only and is not intended for customer use. Do not
write to shaded locations.
(0X06[3]) Delayed Frame Sync Enable. This bit shall be enabled if the daisy chain mode is
used.
1 = Delayed frame sync for daisy chaining of additional 73M1903C devices.
0 = FSD tristated, for normal operation.
GPIO REGISTERS
The TERIDIAN 73M1903C modem AFE device provides 8 user definable I/O pins. Each pin is
programmed separately as either an input or an output by a bit in a direction register. If the bit in the
direction register is set high, the corresponding pin is an input whose value is read from the GPIO data
register. If it is low, the pin will be treated as an output whose value is set by the GPIO data register.
To avoid unwanted current contention and consumption in the system from the GPIO port before the
GPIO is configured after a reset, the GPIO port I/Os are initialized to a high impedance state. The input
structures are protected from floating inputs, and no output levels are driven by any of the GPIO pins.
The GPIO pins are configured as inputs or outputs when the host controller (or DSP) writes to the GPIO
direction register. The GPIO direction and data registers are initialized to all ones (FFh) upon reset.
Page: 13 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Register02 (DATA): Address 02h
Reset State FFh
BIT 7
BIT 6
GPIO7
GPIO6
GPIO(7:0)
BIT 5
GPIO5
BIT 4
GPIO4
BIT 3
GPIO3
BIT 2
GPIO2
BIT 1
GPIO1
BIT 0
GPIO0
(0X02[7:0])
Bits in this register will be asserted on the GPIO(7:0) pins if the
corresponding direction register bit is a 0. Reading this address will return data reflecting
the values of pins GPIO(7:0).
Register03 (DIR): Address 03h
Reset State FFh
BIT 7
BIT 6
DIR7
DIR6
DIR(7:0)
BIT 5
DIR5
BIT 4
DIR4
BIT 3
DIR3
BIT 2
DIR2
BIT 1
DIR1
BIT 0
DIR0
(0X03[7:0])
This register is used to designate the GPIO pins as either inputs or
outputs. If the register bit is reset to ‘0’, the corresponding GPIO pin is programmed as an
output. If the register bit is set to a “1”, the corresponding pin will be configured as an input.
PLL CONFIGURATION REGISTERS
Register08 (PLL_PSEQ): Address 08h
Reset State 00h
BIT 7
BIT 6
Pseq(7:0)
BIT 5
BIT 4
BIT 3
Pseq(7:0)
BIT 2
BIT 1
BIT 0
(0X08[7:0])
This corresponds to the sequence of divisor. If Prst(2:0) setting in
Register09 is 00, this register is ignored.
Register09 (PLL_RST): Address 09h
Reset State 0Ah
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
Prst(2:0)
Pdvsr(4:0)
Prst(2:0) represents the rate at which the sequence register is reset.
Pdvsr(4:0) represents the divisor.
BIT 1
BIT 0
Register0A (PLL_KVCO): Address 0Ah
Reset State 22h
BIT 7
BIT 6
BIT 5
Ichp(3:0)
BIT 4
BIT 3
Reserved
BIT 2
BIT 1
BIT 0
Kvco(2:0)
Ichp(3:0)
(0X0A[:47]) represents the size of the charge pump current in the PLL. This charge pump
current can be calculated with Ichp = 2.0µA* (2 + Ichp0 + Ichp1 * 21 + Ichp2 * 22+Ichp3 * 2^3 )*
(T/To), where To=300 C° and T=Temperature in K°.
Bit 3 is a reserved control bit. This bit shall remain “0” always.
Kvco(2:0) (0X0A[2:0]) Represents the magnitude of Kvco associated with the VCO within PLL.
Page: 14 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Kvco2
0
0
0
0
1
1
1
1
Kvco1
0
0
1
1
0
0
1
1
Kvco0
0
1
0
1
0
1
0
1
Fvco
33 MHz
36 MHz
44 MHz
48 MHz
57 MHz
61 MHz
69 MHz
73 MHz
Kvco
38MHz/v
38MHz/v
40MHz/v
40MHz/v
63MHz/v
63MHz/v
69MHz/v
69MHz/v
Table 3: Fvco and Kvco settings at 25°C
Register0B (PLL_DIV): Address 0Bh
Reset State 12h
BIT 7
BIT 6
Unused
Ndvsr(6:0)
BIT 5
(0X0B[6:0])
BIT 4
BIT 3
Ndvsr(6:0)
BIT 2
BIT 1
BIT 0
Represents the divisor. If Nrst{2:0] =0 this register is ignored.
Register0C (PLL_SEQ): Address 0Ch
Reset State 00h
BIT 7
BIT 6
Nseq(7:0)
BIT 5
(0X0C[7:0])
BIT 4
BIT 3
Nseq(7:0)
BIT 2
BIT 1
BIT 0
BIT 1
Nrst(2:0)
BIT 0
Represents the divisor sequence.
Register0D (XTAL_BIAS): Address 0Dh
Reset State 48h
BIT 7
BIT 6
Xtal(1:0)
Xtal(1:0)
Nrst(2:0)
BIT 5
BIT 4
Reserved
BIT 3
-
BIT 2
(0X0D[7:6]) Crystal Oscillator bias current selection
00 = Xtal osc. bias current at 120µA
01 = Xtal osc. bias current at 180µA
10 = Xtal osc. bias current at 270µA
11 = Xtal osc. bias current at 450µA
If OSCIN is used as a Clock input, “00” setting should be used to save power.
(0X0D[2:0]) Represents the rate at which the NCO sequence register is reset.
The address 0Dh must be the last register to be written to when effecting a change in PLL.
Page: 15 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Register0E (PLL_LOCK): Address 0Eh
Reset State 00h
BIT 7
BIT 6
Frcvco
PwdnPLL
Frcvco
PwdnPll
LockDet
BIT 5
LockDet
BIT 4
-
BIT 3
-
BIT 2
-
BIT 1
-
BIT 0
-
(0X0E[7]) Force Vco as System clock Enable.
0 = Xtal oscillator as system clock.
1 = forces VCO as system clock. This bit is reset to ‘0’ upon reset, PwdnPll = 1 or ENFE = 0.
Both PwdnPll and ENFE are delayed coming out of digital section to keep PLL alive long
enough to transition the system clock to crystal clock when Frcvco is reset by PwdnPLL or
ENFE.
(0X0E[6]) PLL Power down Enable Please refer to the Table 4 Below.
1 = forces Power down of PLL analog section.
0: normal operation
(0X0E[5]) PLL Lock indicator. Read only.
1 = PLL locked
0 = PLL not locked.
ENFE
(Register00 bit7)
0
1
1
PwdnPll
(Register0E bit6)
X
0
1
PLL
PLL Power Off
PLL Power On
PLL Power Off
Table 4: PLL Power Down
Page: 16 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
CLOCK GENERATION
Crystal Oscillator and Prescaler NCO
The crystal oscillator operates over wide choice of crystals (from 4.9MHz to 27MHz) and it is first input to
a Numerically Controlled Oscillator (NCO) -based prescaler (divider) prior to being passed onto an onchip PLL. The intent of the prescaler is to convert the crystal oscillator frequency, Fxtal, to a convenient
frequency to be used as a reference frequency, Fref, for the PLL. The NCO prescaler requires a set of
three numbers to be entered through the serial port (Pseq[7:0], Prst[2:0] and Pdvsr[2:0]. The PLL also
requires 3 numbers as for programming; Ndvsr[6:0], Nseq[7:0], and Nrst[2:0]. The following is a brief
description of the registers that control the NCOs, PLLs, and sample rates for the TERIDIAN 73M1903C
IC. The tables show some examples of the register settings for different clock and sample rates. A more
detailed discussion on how these values are derived can be found in Appendix B.
LockDet
0
Fref
FXtal
NCO
prescaler
System
Clock
Up
PFD
Kd
Charge
Pump
R1
VCO
Kvco
C2
C1
Divide
by 2/1
1
Dn
Ichp Control
3
Kvco Control
3
NCO
FrcVco
Figure 6: Clock Generation
Page: 17 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Reg Address
Ichp Kvco
8h 9h Ah Bh Ch Dh* (µA) [2:0]
Fs(kHz)
7.2
DA
EF
20
13
10
C4
8
0
8.0
DA
EF
31
15
04
C2
10
1
2.4*8/7*3 = 8.22857142858
80
F5
41
1D
06
C2
12
1
8.4
DA
EF
31
16
14
C4
10
1
9.0
DA
EF
31
18
XX
C0
10
1
9.6
DA
EF
32
19
1A
C4
10
2
2.4*10/7*3 = 10.2857142857
DA
EF
43
1B
54
C6
12
3
2.4*8/7*4 = 10.9714285714*
40
C7
23
0D
A4
C7
8
3
11.2*
54
C7
23
0E
10
C4
8
3
12.0
DA
EF
24
20
XX
C0
8
4
12.8*
80
E8
15
11
0E
C3
6
5
2.4*10/7*4 = 13.7142857143
54
CB
26
1A
0E
C3
8
6
14.4
DA
EF
46
26
14
C4
12
6
16.0
A4
E9
17
19
1A
C4
6
7
Table 7: Clock Generation Register Settings for Fxtal = 27MHz
Reg Address
Ichp Kvco
8h 9h Ah Bh Ch Dh* (µA) [2:0]
Fs(kHz)
7.2
XX
0A
8.0
XX
0A
2.4*8/7*3 = 8.22857142858
0E
68
10
0D
02
C1
6
0
11
0F
XX
C0
6
1
11
0D
02
C1
6
1
8.4
XX
0A
21
0F
0E
C3
8
1
9.0
XX
0A
21
10
FE
C7
8
1
9.6
XX
0A
22
12
XX
C0
8
2
2.4*10/7*3 = 10.2857142857
04
49
23
12
XX
C0
8
3
2.4*8/7*4 = 10.9714285714
0E
68
23
12
XX
C0
8
3
11.2
XX
0A
23
15
XX
C0
8
3
12
XX
0A
14
16
02
C1
6
4
12.8
XX
0A
15
18
XX
C0
6
5
2.4*10/7*4 = 13.7142857143
XX
07
16
12
XX
C0
6
6
14.4
XX
0A
26
1B
XX
C0
8
6
16.0
XX
08
17
18
XX
C0
6
7
Table 8: Clock Generation Register Settings for Fxtal = 24.576MHz
Page: 18 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Reg Address
Fs(kHz)
8h
Ichp Kvco
9h Ah Bh Ch Dh* (µA) [2:0]
7.2
XX
04
20
0E
14
C4
8
0
8.0
XX
04
31
10
XX
C0
10
1
8.4
XX
04
31
10
1E
C4
10
1
9.0
XX
04
31
12
XX
C0
10
1
9.6
XX
04
32
13
10
C4
10
2
2.4*8/7*4 = 10.9714285714
02
23
33
13
10
C4
10
3
11.2
XX
04
33
16
14
C4
10
3
12
XX
04
24
18
XX
C0
8
4
12.8
XX
04
35
19
1A
C4
10
5
14.4
XX
08
66
39
1A
C4
16
6
16.0
XX
03
17
18
XX
C0
6
7
Table 9: Clock Generation Register Settings for Fxtal = 9.216MHz
Reg Address
Fs(kHz)
8h
7.2
8.0
2.4*8/7*3 = 8.22857142858
Ichp Kvco
9h Ah Bh Ch Dh* (µA) [2:0]
DA EF 30
15 1A C4 10
02 2C 31
13
08
72
0
10 C4 10
1
41 1C 3E C5 12
1
8.4
DA EF 41
9.0
08
6
1
9.6
DA EF 42 1C 1E C4 12
2
2.4*10/7*3 = 10.2857142857
DA EF 43 1E 7E C6 12
3
2.4*8/7*4 = 10.9714285714
3E A9
76 C6 10
3
21 1A C4 14
3
11.2
66
33
DA EF 53
12
08
66
19
10 C4 12
11 0A 1E C4
14
14 0E 14 C4
6
1
4
12.8
DA EF 45
26
14 C4 12
5
2.4*10/7*4 = 13.7142857143
10 8C 46
20
80 C7 12
6
14.4
54 CA 46 1C 3E C5 12
6
16.0
A4
7
E9
17
1C
1E
C4
6
Table 10: Clock Generation Register Settings for Fxtal = 24.000MHz
Reg Address
Fs(kHz)
7.2
16.0
Ichp Kvco
8h 9h Ah Bh Ch Dh* (µA) [2:0]
0
92 F4 50 1A 06 C2 14
40
CA
17
1D
02
C1
6
7
Table 11: Clock Generation Register Settings for Fxtal = 25.35MHz
Page: 19 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
ANALOG I/O
Figure 7 shows the block diagram of the analog front end. The analog interface circuit uses differential
transmit and receive signals to and from the external circuitry.
The hybrid driver in the TERIDIAN 73M1903C IC is capable of connecting directly, but not limited to, a
transformer-based Direct Access Arrangement (DAA). The hybrid driver is capable of driving the DAA’s
line coupling transformer and load impedance. The hybrid drivers can also drive high impedance loads
without modification.
An on-chip band gap voltage is used to provide an internal voltage reference and bias currents for the
analog receive and transmit channels. The reference derived from the bandgap, nominally 1.25 Volts, is
multiplied to 1.36 Volts and output at the VREF pin. Several voltage references, nominally 1.25 Volts, are
used in the analog circuits. The band gap and reference circuits are disabled after a chip reset since the
ENFE (Register00 bit7) is reset to a default state of zero. When ENFE=0, the band gap voltage and the
analog bias currents are disabled. In this case all of the analog circuits are powered down and draw less
than 5 µA of current.
A clock generator (CKGN) is used to create all of the non-overlapping phase clocks needed for the time
sampled switched-capacitor circuits, ASDM, DAC1, and TLPF. The CKGN input is 2 times the
analog/digital interface sample rate or 3.072MHz clock for Fs=8kHz.
ANALOG
DIGITAL
Decimating
Filter
Anti-Alias Filter
RXAP
AAF
MUX
RXAN
Analog
Sigma-Delta
Modulator
Out
AMUX1
BGAP
CKGN
Bandgap
Clock Generator
OPSR
-
TXAP2
TXAN2
Transmit
Low Pass
Filter
Hybrid Drivers
15:0
Serial
Port
PLL/
CLKDIV
phase clocks
(1.536 MHz)
Digital
Sigma-Delta
Modulator
SMFLT
TXAP1
TXAN1
DDEC
Clocks
sck (3.072 MHz)
vreftx
+
rbi
t
gain
phase clocks (1.536 MHz)
VBG
1
MUX
ASDM
vrefrx
SE
L
analb
rbs
Outp
DAC
TLPF
Outn
In
tbs
MUX
DAC
1
1
DSDM
15:0
tbit
dtmfbst
DigLoopbk
Ext Loopbk
Int Loopbk
analb
txbst
SFR
REGISTERS
Figure 7: Analog block diagram
Page: 20 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
MODEM TRANSMITTER
The modem transmitter begins with a 48 tap Transmit Interpolation Filter (TIF) that takes in the 16-bit,
two’s compliment numbers (TXD) at SDIN pin at Fs=8kHz rate. It up-samples (interpolates) the data to
16kHz rate rejecting the images at multiples of 8kHz that exist in the original TXD data stream and
outputs 16-bit, two’s compliment numbers to a digital sigma-delta modulator.
The gain of the
interpolation filter is 0.664 (–3.56dB) at dc.
The digital sigma-delta modulator (DSDM) takes 16-bit, two’s compliment numbers as input and
generates a 1’s bit stream which feeds into a D to A converter (DAC1). The gain through DSDM is 1.0.
DSDM takes 16-bit, two’s compliment numbers as input and generates a 1’s bit stream that feeds into a D
to A converter (DAC1).
DAC1 consists of a 5-tap FIR filter and a first order switched capacitor low pass filter both operating at
1.536MHz. It possesses nulls at multiples of 384kHz to allow decimation by the succeeding filter.
DAC1’s differential output is fed to a 3rd-order switched-capacitor low pass filter (TLPF). The output of
TLPF drives a continuous time smoothing filter. The sampling nature of the transmitter leads to an
additional filter response that affects the in-band signals. The response is in the form of sin(x)/x and can
be expressed as 20*log [(sin(PI*f/fs))/(PI*f/fs)] where f = signal frequency and fs = sample frequency = 16
kHz. Figure 8 and Figure 9 shows the frequency response of the transmit path from TXD to TXAP/TXAN.
The transmit bandwidth is about 3.65kHz when Fs=8kHz. The bandwidth scales with Fs, the sampling
rate. In case of Fs=9.6kHz , then the bandwidth is 3.65kHz x 9.6/8 = 4.38kHz and Fs=10.28kHz, the
bandwidth is 3.65kHz x 10.28/8 = 4.69kHz. This is applicable for both transmit and receive path filters.
Figure 8: Overall TX path frequency response at 8kHz sample rate
Page: 21 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Figure 9: Frequency response of TX path for DC to 4kHz in band signal at 8kHz sample rate
TRANSMIT LEVELS
The 16-bit transmit code word written by the DSP to the Digital Sigma-Delta Modulator (DSDM) (via TIF)
has a linear relationship with the analog output signal. So, decreasing a code word by a factor of 0.5 will
result in a 0.5 (-6dB) gain change in the analog output signal.
The following formula describes the relationship between the transmit code word and the output level at
the transmit pins (TXAP/TXAN):
Vout (V) = 2 * code/32,767 * DSDMgain * dacGAIN * VREF * TLPFgain * SMFLTgain * FreqFctr
Vout is the differential peak voltage at the TXAP and TXAN pins.
Code is the 16-bit, two’s compliment transmit code word written out by the DSP to the DSDM (via TIF).
The code word falls within a range of ± 32,767. For a sinusoidal waveform, the peak code word should
be used in the formula to obtain the peak output voltage.
DSDMgain is the scaling factor used on the transmit code word to reduce the possibility of saturating the
modulator. This value is set to 0.640625(–3.555821dB) at dc in the 48 tap transmit interpolation filter
(TIF) that precedes DSDM.
dacGAIN is the gain of the DAC. The value dacGAIN is calculated based on capacitor values inside
DAC1 and dacGAIN=8/9=0.8889. The number 32,767 refers to the code word that generates an 82%
“1’s” pulse density at the output of the DSDM. As can be seen from the formula, the D to A conversion is
dependent on the level of VREF. Also when DTMFBST bit is set, VREF is increased from 1.36V to
Page: 22 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
1.586V to allow higher transmit level or 16.6% increase in gain. This bit is intended for enhancing the
DTMF transmit level and should not be used in data mode.
TLPFgain is the gain of TLPF and nominally equals to 0.00dB or 1.0.
SMFLTgain is the gain of SMFLT and nominally equal to 1.445 or 3.2dB.
When TXBST0 bit is set, the gain is further increased by 1.65dB (1.21) for the total of 4.85 dB. This is to
accommodate greater hybrid insertion loss encountered in some applications.
FreqFctr shows dependency of the entire transmit path on frequency. See Figure 8.
With the transmit code word of +/- 32,767, the nominal differential swing at the transmit pins at dc is:
Vout (V) = 2 * code/32,767 * DSDMgain * dacGAIN * VREF * TLPFgain * SMFLTgain * FreqFctr
= 2 * 32,767/32767 * 0.6640625 * 0.8889 * 1.36 * 1.0 * 1.4454 * 1.0 = 2.31Vpk diff.
When DTMFBST bit is set, Vout (V) = 1.166 * 2.31= 2.693Vpk diff.
When TXBST0 bit is set, Vout (V) = 1.21 * 2.31= 2.795Vpk diff. (1)
When both DTMFBST and TXBST0 are set to 1, Vout (V) = 2.795 * 1.166 = 3.259Vpk diff.
[1] If not limited by power supply or internal reference.
Page: 23 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
TRANSMIT POWER - dBm
To calculate the analog output power, the peak voltage must be calculated and the peak to rms ratio
(crest factor) must be known. The following formula can be used to calculate the output power, in dBm
referenced to 600Ω.
Pout (dBm) = 10 * log [ ( Vout (V) / cf )2 / ( 0.001 * 600 ) ]
The following example demonstrates the calculation of the analog output power given a 1.2kHz FSK tone
(sine wave) with a peak code word value of 11,878 sent out by the DSP.
The differential output voltage at TXAP-TXAN will be:
With FreqFctr = 1.02, (See Figure 8)
Vout (V) = 2 * (11,878/32,767) * 0.6640625 * 0.8889 * 1.36 * 1.0 * 1.4454 * 1.02 = 0.841Vpk.
The output signal power will be:
Pout (dBm) = 10 * log [(0.841 / 1.41)2 / (0.001 * 600) ] = - 2.29dBm.
Transmit Type crest factor Max line level
V.90
4.0
-12dBm
QAM
2.31
-9dBm
DPSK
1.81
-9dBm
FSK
1.41
-9dBm
DTMF
1.99
-5.7dBm
Table 13: Peak to RMS ratios and maximum transmit
levels for various modulation types
MODEM RECEIVER
A differential receive signal applied at the RXAP and RXAN pins or the output signal at TXAP and TXAN
pass through a multiplexer, which selects the inputs to the ADC. In normal operation, RXAP/RXAN are
selected. In analog loopback mode, TXAP/TXAN are selected. The DC bias for the RXAP/RXAN inputs
is supplied from TXAP/TXAN thru the external DAA in normal conditions. It can be supplied internally, in
the absence of the external DAA, by setting RXPULL bit in Register02.
The output of the multiplexer goes into a second-order continuous time, Sallen-Key, low-pass filter (AAF)
with a 3dB point at approximately 40kHz. The filtered output signal is the input to an analog sigma-delta
modulator (ASDM), clocked at an over sampling frequency of 1.536MHz for Fs = 8kHz, which converts
the analog signal to a serial bit stream with a pulse density that is proportional to the amplitude of the
analog input signal.
There are three gain control bits for the receive path. The RXGAIN bit in control register one results in a
+20dB gain of the receive signal when set to a “1”. This 20dB of gain compensates for the loss through
the DAA while on hook. It is used for Caller ID reception. This gain is realized in the front end of ASDM.
Page: 24 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
The other gain bits in control register 1, RXG1:0, compensate for differences in loss through the receive
path.
RXG1
RXG0
Receive Gain Setting
0
0
1
1
0
1
0
1
6dB
9dB
12dB
0dB
Table 12: Receive Gain
The output of ASDM is a serial bit stream that feeds multiple digital sinc3 filters. The filters are
synchronized so that there is one sample available after every 96 analog samples or at a rate of 16kHz
for Fs=8kHz. The output of the sinc3 filter is a 17 bit, two’s compliment number representing the
amplitude of the input signal. The sinc3 filter, by virtue of holding action (for 96 sample period), introduces
a droop in the passband that is later corrected for by a 48-tap FIR filter that follows.
The output of the sinc3 filter is input to another 48 tap digital FIR filter that provides an amplitude
correction as well as rejecting noise above Fs/2 or 4kHz for Fs=8kHz. The output of this filter is then
decimated by a factor of 2; so, the final output is 16 bit, two’s compliment samples at a rate of 8 kHz.
Figure 10 and Figure 11 depict the sinc3 filter’s frequency response of ASDM along with the 48 tap digital
FIR response that compensates for it and the resulting overall response of the receiver.
Figure 10: Overall receiver frequency response at 8kHz sample rate
Page: 25 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Figure 11: Rx passband response at 8kHz sample rate
It is important to keep in mind that the receive signal should not exceed 1.16Vpk-diff for proper
performance for Rxg=11 (0dB). In particular, if the input level exceeds a value such that one’s density of
RBS exceeds 99.5%, sinc3 filter output will exceed the maximum input range of the decimation filter and
consequently the data will be corrupted. Also for stability reasons, the receive signal should not exceed
1.16Vpk differentially. This value is set at around 65% of the full receive signal of 1.791Vpkdiff at
RXAP/RXAN pins that “would” corresponds to ASDM putting out all ones.
Figure 12 and Figure 13 show the spectrum of 1kHz tone received at RXAP/RXAN of 1.16Vpk-diff and
0.5kHz and 1.0kHz tones of 0.6Vpk-diff each, respectively for Fs=8kHz. Note the effect of FIR
suppressing the noise above 4kHz but at the same time enhancing (in order to compensate for the
passband droop of sinc3 filter) it near the passband edge of 4kHz.
The bandwidth of the receive filter is about 3.585kHz when Fs=8kHz. The bandwidth scales with Fs, the
sampling rate. Please refer to the MODEM TRANSMITTER section for more information.
Page: 26 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Figure 12: RXD Spectrum of 1kHz tone
Figure 13: RXD Spectrum of 0.5kHz, 1kHz, 2kHz, 3kHz and 3.5kHz tones of Equal Amplitudes
Page: 27 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
TEST MODES
There are two loop back test modes that affect the configuration of the analog front end. The internal
loop back mode connects the serial bit stream generated by the analog receiver to the input of the analog
transmitter. This loop back mode is similar to a remote analog loop back mode and can be used to
evaluate the operation of the analog circuits. When using this loop back mode, the TXAN/TXAP pins
should not be externally coupled to the RXAP/RXAN pins. Set bit 4 (INTLB) in register 01h (CTRL2) to
enter this loop back mode.
The second loop back test mode is the external loop back mode, or local analog loop back mode. In this
mode, the analog transmitter outputs are fed back into the input of the analog receiver. Set bit 5 (ANALB)
in register 01h (CTRL2) to enter this loop back mode. In this mode, TBS must be kept to below a value
that corresponds to less than 1.16V/2.31V x -6dB = 25% of the full scale code of +/- 32768 at TXD in
order to ensure that the receiver is not overdriven beyond the maximum of 1.16Vpkpk diff for
Rxg=11(0dB) setting. See Table 16 on page 32 for the maximum allowed transmit levels. Check the
transmitted data against received data via serial interface. This tests the functionality of essentially all
blocks, both digital and analog, of the chip.
There is a third loopback mode that bypasses the analog circuits entirely. Digital loop back forces the
transmitter digital serial bit stream (from DSDM) to be routed into the digital receiver’s sinc3 filters. Set bit
6 (DIGLB) in register 01h (CTRL2) to enter this loop back mode.
POWER SAVING MODES
The 73M1903C has only one power conservation mode. When the ENFE, bit 7 in register 00h, is zero
the clocks to the filters and the analog are turned off. The transmit pins output a nominal 80kΩ
impedance. The clock to the serial port is running and the GPIO and other registers can be read or
updated.
Page: 28 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
ELECTRICAL SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS
Operation outside these rating limits may cause permanent damage to this device.
PARAMETER
Supply Voltage
Pin Input Voltage (except OSCIN)
Pin Input Voltage (OSCIN)
RATING
-0.5V to +4.0V
-0.5V to 6.0V
-0.5V to VDD + 0.5V
RECOMMENDED OPERATING CONDITIONS
PARAMETER
Supply Voltage (VDD) with respect to VSS
Oscillator Frequency
Operating Temperature
Page: 29 of 46
RATING
3.0V to 3.6V
24.576 MHz ±100ppm
-40C to +85°C
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
DIGITAL SPECIFICATIONS
DC CHARACTERISTICS
PARAMETER
Input Low Voltage
Input High Voltage
(Except OSCIN)
Input High Voltage
OSCIN
Output Low Voltage
(Except OSCOUT, FS,
SCLK, SDOUT)
Output Low Voltage
OSCOUT
Output Low Voltage
FS,SCLK,SDOUT
Output High Voltage
(Except OSCOUT, FS,
SCLK, SDOUT)
Output High Voltage
OSCOUT
Output High Voltage
FS,SCLK,SDOUT
Input Low Leakage
Current
(Except OSCIN)
Input High Leakage
Current (Except
OSCIN)
Input Leakage Current
OSCIN
Input High Leakage
Current
OSCIN
Condition
VIL
MIN
-0.5
MAX
0.2 * VDD
UNIT
V
VIH1
0.7 VDD
5.5
V
VIH2
0.7 VDD
VDD + 0.5
V
IOL = 4mA
0.45
V
IOL = 3.0mA
0.7
V
VOL
IOL = 1mA
0.45
V
VOH
IOH = -4mA
VDD - 0.45
V
VOHOSC
IOH =-3.0mA
VDD - 0.9
V
VOH
IOH = -1mA
VDD - 0.45
V
IIL1
VSS < Vin < VIL1
1
µA
IIH1
VIH1 < Vin < 5.5
1
µA
IIL2
VSS < Vin < VIL2
1
30
µA
IIH2
VIH2 < Vin < VDD
1
30
µA
9
12.0
mA
10.3
13.4
mA
11.8
14.5
mA
12.2
16.0
mA
2
2.5
mA
VOL
VOLOSC
IDD current at 3.0V – 3.6V Nominal at 3.3V
IDD Total current
Fs=8kHz,
IDD
Xtal=27MHz
IDD Total current
Fs=11.2kHz,
IDD
Xtal=27MHz
IDD Total current
Fs=14.4kHz,
IDD
Xtal=27MHz
IDD Total current
Fs=16.0kHz,
IDD
Xtal=27MHz
IDD Total current
IDD
ENFE=0
Page: 30 of 46
NOM
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
AC TIMING
PARAMETER
SCLK Period (Tsclk) (Fs=8kHz)
SCLK to FS Delay (td1)
SCLK to FS Delay (td2)
SCLK to SDOUT Delay (td3) (With 10pf load)
Setup Time SDIN to SCLK (tsu)
Hold Time SDIN to SCLK (th)
MIN
15
10
NOM
1/2.048MHz
--
MAX
20
20
20
-
UNIT
ns
ns
ns
ns
ns
ns
Table 14: -Serial interface Timing
td1
td2
tclk
SCLK
FS
RX15
SDOUT
RX14
RX1
RX0
TX
TX0
td3
tsu
SDIN
TX15
TX14
th
Figure 14: Serial Port Data Timing
Page: 31 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
ANALOG SPECIFICATIONS
DC SPECIFICATIONS
VREF is not brought out to a pin on the 73M1903C. This specification is for information only. The VREF
voltage may be measured as the quiescent DC level at the transmit pins.
Parameter
VREF
VREF Noise
VREF PSRR
Test Condition
VDD= 3.0V - 3.6V.
300Hz-3.3kHz
300Hz-30kHz
Min
Nom
1.36
-86
Max
-80
40*
Units
V
dBm600
dB
Table 15: Reference Voltage Specifications
AC SPECIFICATIONS
The table below shows the maximum transmit levels that the output drivers can deliver before distortion
through the DAA starts to become significant. The loss though the DAA transmit path is assumed to be 7
dB. The signals presented at TXAP and TXAN are symmetrical. The transmit levels can be increased by
setting either TXBST0 (+1.5dB) or/and DTMFBST (+0.83dB) for the combined total gain of 2.33dB.
These can be used where higher-level DTMF tones are required.
MAXIMUM TRANSMIT LEVELS
Maximum
Maximum singleSingle-ended rms Single-ended
differential line
ended level at
peak to
Voltage at TXA Peak Voltage at
level (dBm0)
TXA pins (dBm) rms ratio
pins (V)
TXA pins (V)
Transmit Type
VPA=2.7V to 3.6V; All rms and peak voltages are relative to VREF
-12.0
-11.0
4
V.90
QAM
-7.3
-6.3
2.31
0.2175
0.377
0.87
0.87
DPSK
FSK
-5.1
-3.0
-4.1
-2.0
1.81
1.41
0.481
0.617
0.87
0.87
DTMF (high tone)
DTMF (low tone)
-7.8
-9.8
-6.8
-8.8
1.41
1.41
0.354
0.283
0.500
0.400
Table 16: Maximum Transmit Levels
Page: 32 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
PERFORMANCE
Receiver
Parameter
Input Impedance
Receive Gain
Boost
Total Harmonic
Distortion (THD)
RXG Gain
Passband Gain
Input offset
Sigma-Delta ADC
Modulation gain
Maximum Analog
Signal Level at
RXAP/RXAN
Total Harmonic
Distortion (THD)
Test Conditions
Measured at RXAP/N relative to VREF
RXPULL=HI
Measured at RXAP/N relative to VREF
RXPULL=LO
Rxgain = 1; 1kHz; RXAP/N=0.116Vpk-diff
Gain Measured relative to Rxgain=0
RXGAIN=1 for Fs=8kHz
RXGAIN =1 for Fs=12kHz
RXGAIN =1 for Fs=14.4kHz
THD = 2nd and 3rd harmonic.
RXGAIN =1
Gain Measured relative to RXG[1:0]=11
(0dB) @1 kHz
RXG[1:0]=00
RXG[1:0]=01
RXG[1:0]=10
Input 1.16Vpk-diff at RXA. Measure gain at
0.5kHz, and 2kHz. Normalized to 1kHz.
Gain at 0.5kHz
Gain at 1kHz (Normalized)
Gain at 2.0kHz
Short RXAP to RXAN. Measure input
voltage relative to VREF
Normalized to VBG=1.25V.
Includes the effect of AAF(-0.4dB) with
Bits 1,0 of CTRL2 register (01h) = 00.
Peak voltage measured differentially
across RXAP/RXAN.
Min
Nom
Max
230
Units
kΩ
1.0
MΩ
17.0
16.2
15.7
18.5
17.4
17.2
20.0
18.7
18.7
dB
dB
dB
64
70
5.8
8.8
11.8
6
9
12
6.2
9.2
12.2
dB
dB
dB
-0.29
0.21
-0.2
-0.042
0.000
-0.06
0.2
dB
dB
dB
-30
0
30
MV
41
µV/bit
1.16
Vpk-diff
1kHz 1.16Vpk-diff at RXA with Rxg=11
THD = 2nd and 3rd harmonic.
80
85
DB
Transmit V.22bis low band; FFT run on
ADC samples. Noise in 0 to 4kHz band
-85
-80
DBm
0dBm 1000Hz sine wave at TXAP; FFT
Crosstalk
on Rx ADC samples, 1st four harmonics
-100
DB
Reflected back to receiver inputs.
Note: RXG[1:0] and RXGAIN are assumed to have settings of ‘0’ unless they are specified otherwise.
Noise
Table 17: Receiver Performance Specifications
Page: 33 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Transmitter
Parameter
DAC gain
(Transmit Path Gain)
DC offset –
Differential Mode
DC offset – Common
Mode
TXBST0 Gain
DTMFBST Gain
Total Harmonic
Distortion (THD)
1200Ω Resistor
across TNAN/TXAP
Intermod Distortion
Idle Channel Noise
PSRR
Passband Ripple
Transmit Gain
Flatness
Test Condition
Code word of ± 32,767 @1kHz;
TXBST0=0; DTMFBST=0
Across TXAP and TXAN for
DAC input = 0
Average of TXAP and TXAN for DAC input = 0;
relative to VREF
Code word of ± 32,767 @1kHz;
relative to TXBST0=0; TXBST1=0
Code word of ± 32,767 @1kHz;
relative to TXBST0=0; TXBST1=0
Code word of ± 24,575 (75% scale) @1kHz;
relative to TXBST0=0;TXBST1=0
THD = 2nd and 3rd harmonic.
Code word of ± 26,213 (80% scale) @1kHz;
relative to TXBST0=0;TXBST1=0
THD = 2nd and 3rd harmonic.
Code word of ± 29,490 (90% scale) @1kHz;
relative to TXBST0=1;TXBST1=1
THD = 2nd and 3rd harmonic.
Code word of ± 29,490(90% scale) @1kHz;
relative to TXBST0=1;DTMFBST=1
THD = 2nd and 3rd harmonic
Min
Max
Units
µv/bit
70
-100
100
MV
-80
80
MV
1.65
DB
1.335
DB32
-80
-85
dB
-75
-85
dB
-60
-70
dB
-70
dB
70
dB
below
low
tone
110
µV
At output (TXAP-TXAN): DTMF
1.0kHz, 1.2kHz sine waves, summed
2.0Vpk (-2dBm tone summed with 0dBm tone)
Refer to TBR 21 specifications for description of
complete requirements.
200Hz - 4.0kHz
-30 dBm signal at VPA
300Hz – 30kHz
300Hz - 3.2kHz
Code word of ± 32,767 @1kHz. Measure gain at
0.5kHz, and 2kHz relative to 1kHz.
Gain at 0.5kHz
Gain at 1kHz (Normalized)
Gain at 2.0kHz
Gain at 3.3kHz
Nom
-0.125
0.17
0
0.193
-0.12
40
dB
0.125
dB
dB
dB
dB
dB
Table 18: Transmitter Performance Specifications
Page: 34 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Parameter
Test Condition
Min
Nom
Max
Units
TXAP/N output
TXDIS =1.
impedance
Measure impedance differentially
differentially
between TXAP and TXAN.
(TXDIS=1)
160
kΩ
Txap/n common
TXDIS=1
output offset
Short TXAP and TXAN. Measure the
-20
0
20
mV
(TXDIS=1)
voltage respect to Vbg
Note: TXBST0 and DTMFBS are assumed have setting 0’s unless they are specified otherwise.
Table 19: Transmitter Performance Specifications (continued)
SDOUT
GPIO7
GPIO6
SDIN
SckMode
TYPE
RST
VPD
32
31
30
29
28
27
26
25
PACKAGE OPTIONS
(Drawings not to scale)
VND
1
24
GPIO5
VPD
2
23
GPIO4
GPIO0
3
22
VND
GPIO1
4
21
FSD
GPIO2
5
20
VPPLL
GPIO3
6
19
OSCIN
7
18
OSCOUT
8
17
VNPLL
10
11
12
13
14
15
16
TXAN2
TXAP1
TXAP2
RXAN
RXAP
VNA
VPA
9
SCLK
TXAN1
FS
TERIDIAN
73M1903C
73M1903C QFN 32
Page: 35 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
MECHANICAL DRAWIN
0 .8 5 N O M . / 0 .9 M A X .
5
0 .0 0 / 0 .0 0 5
2.5
0 .2 0 R E F .
1
2.5
2
3
5
S E A T IN G
PLANE
TOP VIEW
S ID E V IE W
0.35 / 0.45
3.0 / 3.75
0.18 / 0.3
CHAMFERED
0.30
1.5 / 1.875
1
2
3
3.0 / 3.75
0.25
1.5 / 1.875
0.5
0.2 MIN.
0.35 / 0.45
0.5
0.25
BOTTOM VIEW
32 pin QFN
Controlling dimensions in mm
Page: 36 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
APPENDIX A
73M1903C DAA Resistor Calculation Guide
TXAP1
R1
RW
CBlock
ACTIVE
INDUCTOR
TXAN1
Bridge
Diode
R1
Hook
Switch
Bead
RING
DETECTOR
Bead
C1
TIP
RING
C1
R3
RXAP
R2
R3
RXAN
R2
Figure 15: Typical DAA block diagram
The following procedure can be used to approximate the component values for the DAA. The optimal
values will be somewhat different due to the effects of the reactive components in the DAA (this is a DC
approximation). Simulations with the reactive components accurately modeled will yield optimal values.
The procedures for calculating the component values in the DAA are as follows. First determine R1. For
a differential transmitter R1 is composed of 2 resistors that represent the difference in resistance between
the total winding resistance of the transformer and the reflected impedance, 600 Ω. This value is usually
supplied by the transformer vendor. The DAA should be designed to reflect 600 Ω when looking in at
TIP/RING. The transformer is normally a 1 to 1 turns ratio, the holding coil and ring detect circuit are high
impedance, and Cblock is a high value so in the frequency band of interest it is negligible. The sum of R2
and R3 is much greater than R1, and the output impedance of the drivers driving TXAP/TXAN are low,
therefore:
Rin 2 . R1 RW Rohswitch 2 . Rbead
RW is the sum of the winding resistance of both sides of the transformer. Measure each side of the
transformer with an Ohmmeter and sum them.
Rohswitch is the on resistance of the Off Hook Switch. Mechanical Relay switches can be ignored, but
Solid State Relays sometimes have an appreciable on resistance.
Rbead is the DC resistance of whatever series RF blocking devices may be in the design.
For Rin equal to 600 Ω:
600 RW Rohswitch 2 . Rbead
R1
2
To maximize THL (Trans-Hybrid Loss), or to minimize the amount of transmit signal that shows up back
on the Receive pins. The RXAP/RXAN pins get their DC bias from the TXAP/TXAN pins. By capacitively
coupling the R3 resistors with the C1 caps, the DC offset can be minimized from the TXAP/TXAN to the
RXAP/RXAN because the DC offset will be divided by the ratio of the R1 resistors to the winding
resistance on the modem side of the transformer.
Page: 37 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
Next make the sum of R2 + R3 much higher than 600 Ω. Make sure they are lower than the input
impedance of the RXAP/RXAN pins; otherwise they can move the frequency response of the input filter.
So let R2 + R3 = 100 KΩ.
100 K
R3
Rwtot 600
1
1200
where
Rwtot RW Rohswitch 2 . Rbead
R2 100 K R3
Use 1% resistors for R1, R2, and R3
To select the value for C1, make the zero at around 10Hz.
1
10
2 . π . 100 K . C1
1
.
.
2 π 100 K . 10
C1 0.15 uF
C1
The blocking cap Cblock should also have the same frequency response, but due to the low impedance,
its value will be much higher, usually requiring a polarized cap. A blocking cap may also be needed on
the modem side of the transformer if the DC offset current of the transmit pins will exceed the current
rating of the transformer.
1
Cblock
2 . π . 600. 10
Cblock 27 uF
When using a wet transformer design as in the following Figure 16, the only difference is that the
R1
TXAP1
RW
Hook
Switch
RING
DETECTOR
R1
TXAN1
C1
Bead
Bead
TIP
RING
C1
R3
R2
RXAP
R3
RXAN
R2
Figure 16: Single transmitter arrangement
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© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
blocking capacitor, Cblock, it is removed. All other equations still hold true.
When both drivers are used for worldwide application, the recommended connections are shown below.
The termination realized when the primary driver is selected is 2R1 + Rwtot;
With the secondary driver is selected it is 2Z4 + Rwtot.
R1
TXAP1
TXAN1
R1
TXAP2
Z4
TXAN2
Z4
RW
ZL
C1
R3
RXAP
R3
R2
R3
RXAN
R3
R2
Figure 17: Dual transmitter arrangement
Still keep R2 + R3 = 100K.
100K
R3
Rwtot + 600
1+
Rwtot + 600 + 1200
and
R2 100 K
R3.
Trans-Hybrid Loss (THL)
Trans-Hybrid Loss is by definition the loss of transmit signal from Tip/Ring to the receive inputs on the
modem IC. This definition is only valid when driving a specific phone line impedance. In reality, phone
line impedances are never perfect, so this definition isn’t of much help. Instead, as an alternate definition
that helps in analysis for this modem design, THL is the loss from the transmit pins to the receive pins. In
this definition the worst-case THL from the transmit pins to the Receive pins is 10.8dB. An insertion loss
of 7dB is assumed accounting for losses due to switch, bridge and transformer.
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© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
APPENDIX B
Crystal Oscillator
The crystal oscillator is designed to operate over wide choice of crystals (from 4.9MHz to 27MHz). The
crystal oscillator output is input to an NCO based pre-scaler (divider) prior to being passed onto an onchip PLL. The intent of the pre-scaler is to convert the crystal oscillator frequency, Fxtal, to a convenient
frequency to be used as a reference frequency, Fref, for the PLL. A set of three numbers– Pdvsr (5 bit),
Prst (3 bit) and Pseq (8 bit) must be entered thru the serial port as follows:
Pdvsr = Integer [Fref/Fxtal];
Prst = Denominator of the ratio (Fref/Fxtal) minus 1 when it is expressed as a ratio of two smallest
integers = Nnco1/Dnco1;
Pseq = Divide Sequence
Fxtal
overflow
Fref
Counter
Pdvsr
Pdvsr +1
mux
count ctrl
Sequence
Register
Sequence
Counter
Rst
Pseq[7:0]
Prst[2:0]
Figure 18: NCO block diagram
Please note that in all cases, pre-scaler should be designed such that pre-scaler output frequency, Fref,
is in the range of 2 ~ 4MHz.
In the first example below, the exact divide ratio required is Fxtal/Fref = 15.625 =125/8. If a divide
sequence of {÷16,÷16,÷15,÷16,÷16,÷15,÷16,÷15} is repeated, the effective divide ratio would be exactly
15.625. Consequently, Pdvsr of 15, the length of the repeating pattern, Prst = 8 –1 =7, and the pattern,
{1,1,0,1,1,0,1,0}, where 0 means Pdvsr, or ÷15, and 1 means Pdvsr +1, or ÷16 must be entered as below.
Example 1: Fxtal = 27MHz, Fref = 1.728MHz.
Pdvsr = Integer [Fxtal/Fref] = 15 =0Fh
Prst[2:0] = 8 – 1 = 7 from Fxtal/Fref = 15.625 =125/8;
Pseq = ÷16,÷16,÷15,÷16,÷16,÷15,÷16,÷15 => {1,1,0,1,1,0,1,0} =DAh.
In the second example, Fxtal/Fref =4.0. This is a constant divide by 4. Thus Pdvsr is 4, Prst = 1 –1 =0
and Pseq = {x,x,x,x,x,x,x,x).
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Modem Analog Front End
DATA SHEET
Example 2: Fxtal = 18.432MHz, Fref = 2.304 MHz.
Pdvsr = Integer [Fxtal/Fref] = 8 = 8h;
Prst[2:0] = 1- 1 = 0 from Fref/Fxtal = 18.432/2.304 = 8/1;
Pseq = {x,x,x,x,x,x,x,x} = xxh
Example 3: Fxtal = 24.576MHz, Fref = 2.4576MHz.
Pdvsr = Integer [ Fxtal/Fref] = 10 = Ah;
Prst[2:0] = 1- 1 = 0 from Fref/Fxtal = 24.576/2.4576 = 10/1;
Pseq = {x,x,x,x,x,x,x,x} = xxh
Example 4: Fxtal = 24.576MHz, Fref = 3.072MHz.
Pdvsr = Integer [ Fxtal/Fref] = 8 = 8h;
Prst[2:0] = 1- 1 = 0 from Fref/Fxtal = 24.576/3.072 = 8/1;
Pseq = {x,x,x,x,x,x,x,x} = xxh
It is also important to note that when Fxtal/Fref is an integer the output of the prescaler is a straight
frequency divider (example 2). As such there will be no jitter generated at Fref. However if Fxtal/Fref is
a fractional number, Fref, at the output of the prescaler NCO would be exact only in an average sense
(example 1) and there will be a certain amount of fixed pattern (repeating) jitter associated with Fref which
can be filtered out by the PLL that follows by appropriately programming the PLL. It is important to note,
however, that the fixed pattern jitter does not degrade the performance of the sigma delta modulators so
long as its frequency is >> 4kHz.
PLL
NCO
Prescaler
Up
Fref
PFD
Charge
Pump
Kd
R1
C2
C1
VCO
Kvco
Divide
by 2/1
Dn
Ichp Control
3
Kvco Control
3
NCO
Figure 19: PLL Block Diagram
73M1903C has a built in PLL circuit to allow an operation over wide range of Fs. It is of a conventional
design with the exception of an NCO based feedback divider. (See Figure 18: PLL Block Diagram).
The architecture of the 73M1903C dictates that the PLL output frequency, Fvco, be related to the
sampling rate, Fs, by Fvco = 2 x 2304 x Fs. The NCO must function as a divider whose divide ratio
equals Fref/Fvco.
Just as in the NCO prescaler, a set of three numbers– Ndvsr ( 7 bits ), Nrst ( 3 bits ) and Nseq ( 8 bits )
must be entered thru a serial port to affect this divide:
Ndvsr = Integer [Fref/Fxtal] ;
Nrst = Denominator of the ratio (Fvco/Fref), Dnco1, minus 1, when it is expressed as a ratio of two
smallest integers = Nnco1/Dnco1;
Nseq = Divide Sequence
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© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
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Modem Analog Front End
DATA SHEET
Example 1: Fs = 7.2kHz or Fvco = 2 x 2304 x 7.2kHz =33.1776MHz, Fref = 1.728MHz.
Ndvsr = Integer [ Fvco/Fref ] = 19
Nrst = 5 – 1 = 4 from Fvco/Fref = 19.2 = 96/5;
Nseq = ÷19, ÷19, ÷19, ÷19, ÷20 => {0,0,0,0,1} =xxx00001 = 01h.
Example 2: Fs = 8.0kHz or Fvco = 2 x 2304 x 8kHz =36.864MHz, Fref = 2.304MHz.
Ndvsr = Integer [Fvco/Fref] = 16 = 10h;
Nrst= 1-1 = 0 from Fvco/Fref = 16/1;
Nseq = {x,x,x,x,x,x,x,x} = xxh.
Example 3: Fs = 9.6kHz or Fvco = 2 x 2304 x 9.6kHz =44.2368MHz, Fref = 2.4576MHz.
Ndvsr = Integer [Fvco/Fref] = 18 = 16h;
Nrst= 1-1 = 0 from Fvco/Fref = 18/1;
Nseq = {x,x,x,x,x,x,x,x} = xxh.
Example 4: Fs = 16.0kHz or Fvco = 2 x 2304 x 16.0kHz =73.728MHz, Fref = 3.072MHz.
Ndvsr = Integer [Fvco/Fref] = 24 =18h;
Nrst= 1-1 = 0 from Fvco/Fref = 24/1;
Nseq = {x,x,x,x,x,x,x,x} = xxh.
It is important to note that in general the NCO based feedback divider will generate a fixed jitter pattern
whose frequency components are at Fref/Accreset2 and its integer multiples. The overall jitter frequency
will be a nonlinear combination of jitters from both pre-scaler and PLL NCO. The fundamental frequency
component of this jitter is at Fref/Prst/Nrst. The PLL parameters should be selected to remove this jitter.
Three separate controls are provided to fine tune the PLL as shown in the following sections.
To ensure quick settling of PLL, a feature was designed into the 73M1903C where Ichp is kept at a higher
value until LockDet becomes active or Frcvco bit is set to 1, whichever occurs first. Thus PLL is
guaranteed to have the settling time of less than one Frame Synch period after a new set of NCO
parameters had been written to the appropriate registers. The serial port register writes for a particular
sample rate should be done in sequence starting from register 08h ending in register 0Dh. 0Dh register
should be the last one to be written to. This will be followed by a write to the next register in sequence
(0Eh) to force the transition of Sysclk from Xtal to Pllclk.
Upon the system reset, the system clock is reset to Fxtal/9. The system clock will remain at Fxtal/9 until
the Host forces the transition, but no sooner the second Frame Synch period after the write to 0Dh.
When this happens, the system clock will transition to PLLclk without any glitches thru a specially
designed deglitch MUX.
Examples of NCO settings
Example 1:
Crystal Frequency = 24.576MHz; Desired Sampling Rate, Fs = 13.714kHz(=2.4kHz x 10/7 x 4)
Step 1. First compute the required VCO frequency, Fvco, corresponding to
Fs = 2.4kHz x 10/7 x 4 = 13.714kHz, or
Fvco = 2 x 2304 x Fs = 2 x 2304 x 2.4kHz x 10/7 x 4 = 63.19543MHz.
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© 2005-2008 TERIDIAN Semiconductor Corporation
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73M1903C
Modem Analog Front End
DATA SHEET
Step 2. Express the required VCO frequency divided by the Crystal Frequency as a ratio of two integers.
This is initially given by :
2 • 2304 • 2.4kHz • 10/7 • 4
24.576MHz
=
Fvco / Fxtal
.
After a few rounds of simplification this ratio reduces to:
Fvco / Fxtal
=
=
18
7
Nnco1
Dnco1
Nnco2
Dnco2
1
7
=(
18
1
)•(
)
1
7
1
18
=
, where Nnco1 and Nnco2 must be < or equal to 8.
The ratio, Nnco1/Dnco1 = 1/7, is used to form a divide ratio for the NCO in prescaler and Nnco2/Dnco2 =
1/18 for the NCO in the PLL.
Prescaler NCO: From Nnco1/Dnco1 = 1/7,
Pdvsr = Integer [nco1/Nnco1] = 7;
Prst[2:0] = Nnco1 – 1 = 0; this means NO fractional divide. It always does ÷7. Thus Pseq becomes
“don’t care” and is ignored.
Pseq = {x,x,x,x,x,x,x,x} = xxh.
PLL NCO: From Nnco2/Dnco2 = 1/18,
Ndvsr = Integer [Dnco2/Nnco2] = 18;
Nrst[2:0] = Nnco2 – 1 = 0; this means NO fractional divide. It always does ÷18. Thus Pseq becomes
“don’t care” and is ignored.
Nseq = {x,x,x,x,x,x,x,x} = xxh.
Example 2:
Crystal Frequency = 24.576MHz; Desired Sampling Rate, Fs = 10.971kHz=2.4kHz x 8/7 x4
Step 1. First compute the required VCO frequency, Fvco, corresponding to
Fs = 2.4kHz x 8/7 x 4 =10.971kHz.
Fvco = 2 x 2304 x Fs = 2 x 2304 x 2.4kHz x 8/7 x 4 = 50.55634MHz.
Step 2. Express the required VCO frequency divided by the Crystal Frequency as a ratio of two integers.
This is initially given by :
Fvco / Fxtal
=
Page: 43 of 46
2 • 2304 • 2.4kHz • 8/7 • 4
24.576MHz
.
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
After a few rounds of simplification this ratio reduces to:
4
18
Fvco / Fxtal = (
)•(
)
35
1
Nnco1
4
Dnco1
35
=
=
Nnco2
1
Dnco2
18
, where Nnco1 and Nnco2 must be < or equal to 8.
The ratio, Nnco1/Dnco1 = 4/35, is used to form a divide ratio for the NCO in pre-scaler and Nnco2/Dnco2
=1/18 for the NCO in the PLL.
Pre-scaler NCO: From Nnco1/Dnco1 = 4/35,
Pdvsr = Integer [ Dnco1/Nnco1 ] = 8;
Prst[2:0] = Nnco1 – 1 = 3;
Dnco1/Nnco1 = 35/4 = 8.75 suggests a divide sequence of {÷9,÷9,÷9,÷8}, or
Pseq = {x,x,x,x,1,1,1,0} = xDh.
PLL NCO: From Nnco2/Dnco2 = 1/18,
Ndvsr = Integer [ Dnco2/Nnco2 ] = 18;
Nrst[2:0] = Nnco2 – 1 = 0; this means NO fractional divide. It always does ÷18. Thus Pseq becomes
“don’t care”.
Nseq = {x,x,x,x,x,x,x,x} = xxh.
Example3:
Crystal Frequency = 27MHz; Desired Sampling Rate, Fs = 7.2kHz
Step 1. First compute the required VCO frequency, Fvco, corresponding to
Fs = 2.4kHz x 3 = 7.2kHz.
Fvco = 2 x 2304 x Fs = 2 x 2304 x 2.4kHz x 3 = 33.1776MHz.
Step 2. Express the required VCO frequency divided by the Crystal Frequency as a ratio of two integers.
This is initially given by :
=
Fvco / Fxtal
2 • 2304 • 2.4kHz • 3
27MHz
.
After a few rounds of simplification this reduces to:
Fvco / Fxtal
=
8
125
Nnco1
Dnco1
Nnco2
Dnco2
=(
96
5
)•(
=
)
.
8
125
5
96
The two ratios are not unique and many other possibilities exist. But for this particular application, they
are found to be the best set of choices within the constraints of Prst and Nrst allowed. (Nnco1, Nnco2
must be less than or equal to 8.)
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© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
The ratio, Nnco1/Dnco1 = 8/125, is used to form a divide ratio for the NCO in prescaler and Nnco2/Dnco2
=5/96 for the NCO in the PLL.
Pre-scaler NCO: From Nnco1/Dnco1 = 8/125,
Pdvsr = Integer [ Dnco1/Nnco1 ] = 15;
Prst[2:0] = Nnco1 – 1 = 7;
Dnco1/Nnco1 = 125/8 = 15.625 suggests a divide sequence of {÷16,÷16,÷15,÷16,÷16,÷15,÷16,÷15}, or
Pseq = {1,1,0,1,1,0,1,0} = DAh.
PLL NCO: From Nnco2/Dnco2 = 5/96,
Ndvsr = Integer [ Dnco2/Nnco2 ] = 19;
Nrst[2:0] = Nnco2 – 1 = 4;
Dnco2/Nnco2 = 19.2 suggests a divide sequence of {÷19, ÷19, ÷19, ÷19, ÷20}, or
Nseq = {x,x,x,0,0,0,0,1} = x1h.
Example4:
Crystal Frequency = 24.576MHz; Desired Sampling Rate, Fs = 16.0kHz
Step 1. First compute the required VCO frequency, Fvco, corresponding to
Fs = 2.4kHz x 20/3 = 16.0kHz.
Fvco = 2 x 2304 x Fs = 2 x 2304 x 2.4kHz x 20/3 = 73.728MHz.
Step 2. Express the required VCO frequency divided by the Crystal Frequency as a ratio of two integers.
This is initially given by :
2 • 2304 • 2.4kHz • 20/3
24.576MHz
=
Fvco / Fxtal
.
After a few rounds of simplification this reduces to:
Fvco / Fxtal
=
24
1
=(
Nnco1
Dnco1
Nnco2
Dnco2
1
8
)•(
=
)
1
8
1
24
The ratio, Nnco1/Dnco1 = 1/1, is used to form a divide ratio for the NCO in prescaler and Nnco2/Dnco2
=1/24 for the NCO in the PLL.
Pre-scaler NCO: From Nnco1/Dnco1 = 1/8,
Pdvsr = Integer [ Dnco1/Nnco1 ] = 8 = 08h,
Prst[2:0] = Nnco1 – 1 = 0; this means NO fractional divide. It always does ÷8. Thus Pseq becomes “don’t
care”.
Pseq = {x,x,x,x,x,x,x,x}= xxh.
PLL NCO: From Nnco2/Dnco2 = 1/24,
Ndvsr = Integer [ Dnco2/Nnco2 ] = 24 = 18h,
Nrst[2:0] = Nnco2 – 1 = 0; this means NO fractional divide. It always does ÷24. Thus Nseq becomes
“don’t care”.
Nseq = {x,x,x,x,x,x,x,x} = xxh.
Page: 45 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
Rev 4.3
73M1903C
Modem Analog Front End
DATA SHEET
ORDERING INFORMATION
PART DESCRIPTION
73M1903C 32-Lead QFN Lead Free
73M1903C 32-Lead QFN Lead Free, Tape and Reel
ORDER NUMBER
73M1903C-IM/F
73M1903C-IMR/F
Data Sheet: This Data Sheet is proprietary to TERIDIAN Semiconductor Corporation (TSC) and sets forth design goals for the described
product. The data sheet is subject to change. TSC assumes no obligation regarding future manufacture, unless agreed to in writing.
This product is sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to
warranty, patent infringement and limitation of liability. TERIDIAN Semiconductor Corporation (TSC) reserves the right to make changes in
specifications at any time without notice. Accordingly, the reader is cautioned to verify that a data sheet is current before placing orders.
TSC assumes no liability for applications assistance.
TERIDIAN Semiconductor Corp., 6440 Oak Canyon, Suite 100, Irvine, CA 92618
TEL (714) 508-8800, FAX (714) 508-8877, http://www.teridian.com
© 2005-2008 TERIDIAN Semiconductor Corporation
Page: 46 of 46
© 2005-2008 TERIDIAN Semiconductor Corporation
01/17/2008– Rev 4.3
Rev 4.3