NOTE: This is a summary document.
The complete document is available
under NDA. For more information,
please contact your local Atmel sales
office.
Features
Highly Integrated DAB Front-end Solution Covering Band III Reception
Convenient Internal Clock Generation, Single Reference Clock
Fractional PLL for VHF
Fully Integrated VCO
High-precision Digitally Tunable Reference Oscillator
Integrated High-performance LNA
Very Flexible Programming of the AGC
Automatically Aligned External Filter Tuning
Simple Three-wire Digital Control Interface for Easy Handling
Single Low Voltage (3.3V) Supply Operation
Low Current Consumption Due to Several Power-down Options
Small SMD Package (QFN 7 mm
7 mm)
Applications
Commercial DAB Receivers
DAB Receiver Solutions for Car Radio Applications
Portable DAB Solutions
1.
Description
The ATR2733 is a front-end monolithic integrated circuit, manufactured using Atmel's
silicon-germanium BiCMOS process (SiGMOS).
The ATR2733 carries out all functions of RF and IF processing, as well as the
clock-signal generation for these functions. Therefore, there is an integrated fractional
PLL, which, equivalent to most of the other functions, can be controlled via an external
digital bus. The RF functions include LNA, down-conversion mixing, amplifying, detec-
tion, and gain control. An external SAW filter is required in the signal path after the RF
functions. Additional amplifiers with detection and control functions are integrated IF
functions.
The device offers several tuning support functions, and was created to simplify the
design and manufacturing process. To this end, the number of external components
are minimal.
The part fits perfectly to Atmel's DAB baseband processor ATR2740.
Figure 1-1.
Block Diagram
Control Unit
RSSI
Gain
Cntl
PWR
Cntl
Vtune
Gen.
VCO
VHF
Frac.PLL
A
A
D
SPI In
te
r
f
a
c
e
Integrated DAB
One-chip Front
End
ATR2733
Preliminary
4926ASDAB04/06
2
4926ASDAB04/06
ATR2733 [Preliminary]
2.
Pin Configuration
Figure 2-1.
Pinning QFN48
VDD
LNAVIN+
LNAVL+
LNAVL-
LNAVIN-
VALNA
AGCREF
GNDLNA
LNAVO+
LNAVO-
VABIAS
CVREF
IF2O+
AGCIF
IF2IN-
IF2IN+
PDFOUTV
TNKREFO
TNKREFI
VTNKREF
VFIL1
VFIL2
VFIL3
GDVCOV
XTAL
B
XTAL
A
VD
I
XO
U
T
MISO
SC
K
NS
S
MOSI
S
W
I
T
CHE
N
WA
GC
VA
IF2
O
-
IF1
O
+
IF1
O
-
RRE
F
E
AG
C
S
AW
IF1
I
N
+
IF1
I
N
-
MIXVIN
+
MIXVIN
-
MIXVO+
MIXVO-
VAVC
O
V
TU
N
V
V
48 47 46 45 44 43 42 41 40 39 38 37
13 14 15 16 17 18 19 20 21 22 23 24
1
2
3
4
5
6
7
8
9
10
11
12
36
35
34
33
32
31
30
29
28
27
26
25
Table 2-1.
Pin Description
Pin
Symbol
Function
1
VDD
Supply for digital circuits
2
LNAVIN+
Input for LNVGA for VHF (differential with pin 8)
3
LNAVL+
Connection for "degeneration coil" (inductance) to GNDLNA for LNVGA for VHF
4
LNAVL-
Connection for "degeneration coil" (inductance) to GNDLNA for LNVGA for VHF
5
LNAVIN-
Input for LNVGA for VHF (differential with pin 5)
6
VALNA
Supply voltage for LNVGAs
7
AGCRF
Connection for capacitor for time constant of AGC of rf parts (LNVGAs, ext. PIN-diode)
8
GNDLNA
Ground for LNVGAs
9
LNAVO+
(Differential) output of LNVGA for VHF and/or mixer for L-Bd.
10
LNAVO-
11
VABIAS
Supply voltage for (internal) voltage and current bias reference circuits
12
CVREF
Connection for capacitor for filtering internal voltage/current reference circuits (capacitor to VABIAS)
13
IF1O+
(Differential) output of IFVGA1
14
IF1O-
15
RREFE
Connection for resistor for current reference (resistor to ground)
16
AGCSAW
Connection for capacitor for time constant of AGC of mixer for VHF
17
IF1IN+
(Differential) input of 1st IFVGA
18
IF1IN-
3
4926ASDAB04/06
ATR2733 [Preliminary]
19
MixVIN+
(Differential) input of mixer for VHF
20
MixVIN-
21
MixVO+
(Differential) output of mixer for VHF
22
MixVO-
23
VAVCOV
Supply voltage (VCO for VHF)
24
TUNVV
Tuning voltage for integrated VCO for VHF (connected to PLL loop filter)
25
GDVCOV
Ground (VCO for VHF)
26
VFIL3
Voltage outputs for frequency tuning of filters for VHF: antenna filter, pre-selection filter
27
VFIL2
28
VFIL1
29
VTNKREF
Output voltage for tuning the "reference tank" (-varactor)
30
TNKREFI
Connection for "reference-tank" for generating the tuning voltages for the external VHF filters (-varactors)
31
TNKREFO
32
PFDOUTV
Output of phase comparator for VCO for VHF (connected to PLL loop-filter)
33
IF2IN+
(Differential) input of 2nd. IFVGA
34
IF2IN-
35
AGCIF
Connection for capacitor for time constant of AGC of IF VGAs
36
IF2O+
(Differential) Output of 2nd. IFVGA
37
IF2O-
38
VA
Supply voltage
39
WAGC
"window AGC" - all AGCs "frozen" - currents to capacitors switched off - necessary during "Null Symbol" or
also during unused symbols left out and powered down using "SWITCHEN" input
40
SWITCHEN
Input for selection between the two "enable" registers - fast change between reduced, "low current" mode
and normal reception mode - current saving capability
41
MOSI
Inputs and outputs of serial bus (see serial bus protocol)
42
NSS
43
SCK
44
MISO
45
XOUT
Crystal oscillator clock output to baseband
if used: ac-couple to baseband (single VCXO-concept)
if not used: short-circuit to GND
46
VDI
Supply voltage from baseband (1.65V ... 3.6V) for adaptation of interface to baseband
47
XTALA
Connection for crystal for reference clock
48
XTALB
Paddle
GND
Ground
Table 2-1.
Pin Description (Continued)
Pin
Symbol
Function
4
4926ASDAB04/06
ATR2733 [Preliminary]
3.
Functional Description
The ATR2733 front-end IC was developed as a tuner IC for DAB reception. It was designed for
operation in VHF BIII (174 MHz to 240 MHz). The front end contains gain-controlled LNAs and a
VHF-band mixer with a fractional PLL. The IF path contains three gain-controlled amplifiers. The
front-end IC allows the use of automatic tuning, which contains an adjustable input filter for VHF
BIII and an adjustable preselection filter for VHF reception.
The high dynamic range of the RF inputs, the use of gain-controlled amplifiers and gain-con-
trolled mixers in the RF and IF path (VHF band) offer the possibility of handling even strong RF
input signals.
The RF and IF parts include AGC functional blocks, which are needed for proper operation. The
thresholds are programmable via a simple serial bus.
The SPI bus is used to adjust and control all functional blocks.
The following sections briefly describe the major functions and features.
3.1
Main Functions
The following description gives a short overview of the general signal flow using the ATR2733
front-end IC for reception of DAB signals. Numbers in the text refer to the numbers in
Figure 3-1
on page 4
:
A DAB signal in the antenna. the signal is band-pass filtered using a filter with low insertion loss.
The internal variable gain LNA for Band III (3)) amplifies the signal. The signal leaves the IC at
point (4), followed by an external preselection filter. This filter has an automatic tuner adjust-
ment; that is, the tuning-voltage-generation block adjusts the pass band of this filter to the
desired frequency. After passing this filter, the RF signal is down-mixed to a fixed IF frequency of
38.912 MHz. The IF signal is amplified and passed to a SAW filter (5). The first IF variable-gain
amplifier is followed by an IF filter at position (6). This filter is used as an anti-alias-filter. Finally,
the DAB signal is amplified using the 2nd IF amplifier. The signal leaves the front-end IC at (7),
giving the signal to the DAB baseband IC.
Figure 3-1.
Functional Block Diagram with Labelled Inputs and Outputs
1)
2)
3)
4)
5)
Control Unit
RSSI
Gain
Cntl
PWR
Cntl
Vtune
Gen.
VCO
VHF
Frac.PLL
A
A
D
SPI In
te
r
f
a
c
e
5
4926ASDAB04/06
ATR2733 [Preliminary]
3.2
AGC in General
There are three AGCs in the ATR2733, one for the RF signals (3), one for the very beginning of
the IF path (mainly VHF mixer), and one for the IF amplifiers (5) down to the output to baseband
(7).
In these AGCs, the output signals of the relevant blocks are amplified, weakly band-pass fil-
tered, rectified, and, finally, low-pass filtered. The voltage derived in this power-measurement
process is compared to a voltage threshold which can be digitally controlled by several bits,
independently of each other. The setting is done via the control bus. Depending on the result of
this comparison, charge pumps feed a positive or negative current in order to charge or dis-
charge external capacitors. The voltage of these external capacitors is used to control the gains
of practically all blocks in the signal path.
By means of the control bus, the current of the AGC charge pump can be selected as specified
in the following table:
The input pin WAGC, set to logical 1, always sets all AGCs to time constant Infinite (meaning
there is practically no current to the AGC capacitors), regardless of the actual status of the bus
settings.
Table 3-1.
Selection of Time Constant Factor
MSB
LSB
Time Constant Factor
0
0
0
Infinite
0
0
1
32
0
1
0
16
0
1
1
8
1
0
0
4
1
0
1
2
1
1
0
1
1
1
1
0.2
PDF 
ZIP