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PDF RF2938 Data sheet ( Hoja de datos )
| Número de pieza | RF2938 | |
| Descripción | 2.4GHZ SPREAD-SPECTRUM TRANSCEIVER | |
| Fabricantes | RF Micro Devices | |
| Logotipo |  |
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2
Typical Applications
• Wireless LANs
• Wireless Local Loop
• Secure Communication Links
RF2938
2.4GHZ SPREAD-SPECTRUM TRANSCEIVER
• Inventory Tracking
• Wireless Security
• Digital Cordless Telephones
Product Description
The RF2938 is a monolithic integrated circuit specifically
designed for direct-sequence spread-spectrum systems
operating in the 2.4GHz ISM band. The part includes a
direct conversion from IF receiver, quadrature demodula-
tor, I/Q baseband amplifiers with gain control and RSSI,
on-chip programmable baseband filters, dual data com-
parators. For the transmit side, a QPSK modulator and
upconverter are provided. The design reuses the IF
SAW filter for transmit and receive reducing the number
of SAW filters required. Two cell or regulated three cell
(3.6V maximum) battery applications are supported by
the part. The part is also designed to be part of a 2.4GHz
chip set consisting of the RF2444 LNA/Mixer and one of
the many RFMD high efficiency GaAs HBT PA’s and a
dual frequency synthesizer.
Optimum Technology Matching® Applied
Si BJT
üSi Bi-CMOS
GaAs HBT
SiGe HBT
GaAs MESFET
Si CMOS
48 47 46 45 44 43 42 41 40 39 38 37
NC 1
36 NC
NC 2
35 NC
PD 3
RX
RX EN 4
TX EN 5
VCC1 6
34 RXQ DATA
33 Q OUT
I
32 RXI DATA
Q
31 I OUT
RX IF IN 7
RX_EN
TX IF IN 8
TX_EN
VCC9 9 TX
TX VGC 10
IF LO 11
VCC8 12
Β2 +45°
-45°
30 VCC4
29 TXQ DATA
I
28 TXQ BP
Q
27 TXI DATA
26 TXI BP
Σ
25 IF1 OUT+
13 14 15 16 17 18 19 20 21 22 23 24
9.00
+ 0.20
0.10 -A-
0.00
9.00
+ 0.10
0.50
4.57
+ 0.10 sq.
0.22
+ 0.05
7° MAX
0° MIN
Exposed pad protrusion
0.0000 to 0.0127 (see note 4).
0.17 MAX.
7.00 1.00
+ 0.10 sq.
+ 0.10
0.60
Dimensions in mm
NOTES:
1. Shaded lead is Pin 1.
+ 0.15
0.10
2. Lead coplanarity - 0.08 with respect to datum "A".
3. Leadframe material: EFTEC 64T copper or equivalent, 0.127 mm (0.005) thick.
4. Solder plating (85/15) on exposed area.
Package Style: TQFP-48 EDF, 9x9
Features
• 45MHz to 500MHz IF Quad Demod
• On-Chip Variable Baseband Filters
• Quadrature Modulator and Upconverter
• 2.7V to 3.6V Operation
• Part of 2.4GHz Radio Chipset
• 2.4GHz PA Driver
Ordering Information
RF2938TR13 2.4GHz Spread-Spectrum Transceiver (Tape & Reel)
RF2938 PCBA Fully Assembled Evaluation Board
11
Functional Block Diagram
RF Micro Devices, Inc.
7628 Thorndike Road
Greensboro, NC 27409, USA
Tel (336) 664 1233
Fax (336) 664 0454
http://www.rfmd.com
Rev A8 010418
2-1
1 page  
RF2938
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Function
NC
NC
PD
RX EN
TX EN
VCC1
RX IF IN
TX IF IN
VCC9
TX VGC
IF LO
VCC8
NC
RF OUT
RF OUT
VCC6
Description
Interface Schematic
No internal connection. May be grounded or connected on adjacent
signal or left floating. Connect to ground for best results.
No internal connection. May be grounded or connected on adjacent
signal or left floating. Connect to ground for best results.
This pin is used to power up or down the transmit and receive base-
band sections. A logic high powers up the quad demod mixers, TX and
RX GmC LPF’s, baseband VGA amps, data amps, and IF LO buffer
amp/ phase splitter. A logic low powers down the entire IC for sleep
Pins
3, 4, 5
10k Ω
mode. Also, see State Decode Table.
VCC
ESD
To Logic
Enable pin for the receiver 15dB gain IF amp and the RX VGA amp.
Powers up all receiver functions when PD is high, turns off the receiver
IF circuits when low. Also, see State Decode Table.
This pin is used to enable the transmit upconverter, buffer amps, 15db
IF amp, quad mod mixers, TX LO buffer, TX VGA, and PA driver. TX EN
is active low, when TX EN <1V, the transmit circuit is active if PD is
high. A logic high (TX EN >2V) disables the transmit IF/RF circuitry and
quad mod. Also, see State Decode Table.
Power supply for RX VGA amplifier, IC logic and RX references.
See pin 3.
See pin 3.
IF input for receiver section. Must have DC blocking cap. The capacitor
value should be appropriate for the IF frequency. External matching to
50Ω recommended. For half duplex operation, connect RX IF IN and
TX IF IN signals together after the DC blocking caps, then run a trans-
mission line from the output of the IF SAW. AC coupling capacitor must
be less than 150pF to prevent delay in switching RX to TX/TX to RX.
Input for the TX IF signal after SAW filter. External DC blocking cap
required. External matching to 50Ω recommended. For half duplex
operation, connect RX IF IN and TX IF IN signals together after the DC
blocking caps, then run a transmission line from the output of the IF
SAW. AC coupling capacitor must be less than 150pF to prevent delay
in switching RX to TX/TX to RX.
See pin 8.
IF
SAW
Filter
50 Ω µstrip
DC Block Pin 7
Pin 8
Power supply for the TX 15dB gain amp and TX VGA.
Gain control setting for the transmit VGA. Positive slope.
IF LO input. Must have DC blocking cap. The capacitor value should be
appropriate for the IF frequency. LO frequency=2xIF. Quad mod/
demod phase accuracy requires low harmonic content from IF LO, so it
is recommended to use an n=3 LPF between the IF VCO and IF LO.
This is a high impedance input and the recommended matching
approach is to simply add a 100Ω shunt resistor at this input to con-
strain the mismatch. This pin requires a 6.5µA DC bias current. This
can be accomplished with a 270kΩ resistor to VCC for 3.3V operation.
VCC
Recommended Matching
Network for IF LO
IF VCO
C2
150 pF
270 kΩ
IF LO
Pin 11
100 Ω
Power supply for IF LO buffer and quadrature phase network.
No internal connection. May be grounded or connected on adjacent
signal or left floating. Connect to ground for best results.
This is the output transistor of the power amp stage. It is an open col-
lector output. The output match is formed by an inductor to VCC, which
supplies DC and a series cap.
CBYP
22 nF
VCC
CBYP
22 nF
VCC
From
TX RF
Image Filter
PA IN
Pin 18
VCC6
Pin 16
14 mA
PA OUT PA OUT
Pin 14
Pin 15
34 mA
Bias Bias
Power
Amp
Output
This is the output transistor of the power amp stage. It is an open col-
lector output. The output match is formed by an inductor to VCC, which
supplies DC and a series cap.
Power supply for the PA driver amp. This inductance to ground via
decoupling, along with an internal series capacitor, forms the interstage
match.
See pin 14.
See pin 14.
11
Rev A8 010418
2-5
5 Page 
TRANSMITTER
TX LPF and Mixers
The transmit section starts with a pair of 5-pole Bessel
filters identical to the filters in the receive section and
with the same 3dB frequency. These filters pre-shape
and band-limit the digital or analog input signals prior
to the first upconversion to IF. These filters have a high
input impedance and expect an input signal of
200mVPP typical. Following these low pass filters are
the I/Q quadrature upconverter mixers. Each of these
mixers is half the size and half the current of the RF to
IF downconverter on the RF2444. Recall that this
upconverted signal may drive the same SAW filter (in
half duplex mode) as the RF2444 and therefore share
the same load. Having the sum of the two BB to IF mix-
ers equal in size and DC current to the RF to IF mixer,
will minimize the time required to switch between RX
and TX, and will facilitate the best impedance match to
the filter.
TX VGA
The AGC after the SAW filter starts with a switch and a
constant gain amplifier of 15dB, which is identical to
the circuitry on the receive IF AGC. This was, done, as
on the RX signal path, so that the input impedance will
remain constant for different TX gain control voltages.
Following this 15dB gain amplifier is a single stage of
gain control offering 15dB gain range. The main pur-
pose of adding this variable gain is to give the system
the flexibility to use different SAW filters and image fil-
ters with different insertion loss values. This gain could
also be adjusted real time, if desired.
RF2938
TX Upconverter
The IF to RF upconverter is a double-balanced differ-
ential mixer with a differential to single-ended con-
verter on the output to supply 0dBm peak linear power
to the image filter. The upconverted SSB signal should
have -6dBm power at this point, and the image will
have the same power, but due to the correlated nature
of the signal and image, the output must support 0dBm
of linear power to maintain linearly.
+6dBm PA Driver
The SSB output of the upconverter is -6dBm of linear
power. The image filter should have at most 4dB of
insertion loss while removing the image, LO, 2LO and
any other spurs. The filter output should supply the PA
driver input -10dBm of power.
The PA driver is a two-stage class A amplifier with
10dB gain per stage and capable of delivering 6dBm
of linear power to a 50Ω load, and has a 1dB compres-
sion point of 12dBm. For lower power applications, this
PA driver can be used to drive a 50Ω antenna directly.
11
Rev A8 010418
2-11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet RF2938.PDF ] | |
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