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PDF LTC1758-2 Data sheet ( Hoja de datos )
| Número de pieza | LTC1758-2 | |
| Descripción | RF Power Controllers with 250kHz Control Loop Bandwidth and 40dB Dynamic Range | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1758-1/LTC1758-2
RF Power Controllers with
250kHz Control Loop Bandwidth and
40dB Dynamic Range
FEATURES
DESCRIPTIO
s Dual Band RF Power Amplifier Control (LTC1758-2)
s Internal Schottky Diode Detector with Improved
Dynamic Range vs LTC1757A
s Wide Input Frequency Range: 850MHz to 2GHz
s Autozero Loop Cancels Offset Errors and
Temperature Dependent Offsets
s Wide VIN Range: 2.7V to 6V
Allows Direct Connection to Battery
s RF Output Power Set by External DAC
s 250kHz Control Loop Bandwidth
s Fast Acquire After Transmit Enable
s Internal Frequency Compensation
s Rail-to-Rail Power Control Outputs
s Power Control Signal Overvoltage Protection
s Low Operating Current: 1mA
s Very Low Shutdown Current: < 1µA
s Available in 8-Pin MSOP (LTC1758-1)
and 10-Pin MSOP (LTC1758-2) Packages
s Pin Compatible with LTC1757A-X
s Improved Start Voltage Accuracy
s Improved PCTL Input Filtering
U
APPLICATIO S
s Single and Dual Band GSM/GPRS Cellular Telephones
s PCS Devices
s Wireless Data Modems
s U.S. TDMA Cellular Phones
The LTC®1758-2 is a dual band RF power controller for
RF power amplifiers operating in the 850MHz to 2GHz
range. The loop bandwidth reduction to 250kHz im-
proves frequency stability when controlling slow turn-on
PAs such as the Philips BGY280, Conexant RM009/
CX77302, Anadigics AWT6102/AWT6107 and the Hitachi
PF08107/PF08123B.
The LTC1758-1 is a single output RF power controller
that is identical in performance to the LTC1758-2 except
that one output (VPCA) is provided. The LTC1758-1 can
be used to drive a single RF or dual channel module with
integral multiplexer. This part is available in an 8-pin
MSOP package.
RF power is controlled by driving the RF amplifier power
control pins and sensing the resultant RF output power
via a directional coupler. The RF sense voltage is peak
detected using an on-chip Schottky diode. This detected
voltage is compared to the DAC voltage at the PCTL pin
to control the output power. The RF power amplifier is
protected against high supply current and high power
control pin voltages.
Internal and external offsets are cancelled over tempera-
ture by an autozero control loop, allowing accurate low
power programming. The shutdown feature disables the
part and reduces the supply current to < 1µA.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
LTC1758-2 Dual Band Cellular Telephone Transmitter
68Ω
VIN 33pF
LTC1758-2
1 10
VIN VCC
Li-Ion
2
RF
9
VPCA
38
SHDN
SHDN
VPCB
47
BSEL
BSEL
TXEN
TXEN
5
GND
6
PCTL
900MHz
RF PA
DIRECTIONAL
COUPLER
DIPLEXER
DAC
1.8GHz /1.9GHz
RF PA
50Ω
1758 TA01
1
1 page  
BLOCK DIAGRA (LTC1758-2)
LTC1758-1/LTC1758-2
DIPLEXER
900MHz
RF PA
Li-Ion
RF PA
1.8GHz/1.9GHz
50Ω
68Ω
33pF
10
VCC
0.02Ω
RSENSE
0.05Ω
METAL
1
VIN
0.02Ω
100Ω
METAL
RF
2
– OVERCURRENT
CS
+
OFFSET
TRIM
GAIN
TRIM
gm
200Ω
VIN
PROGRAMMABLE
200Ω
35k
28pF
35k
GND
5
60µA
60µA
+
RFDET
–
22k
COMPRESSION
BG1
THERMAL
SHUTDOWN
TSDB
OPERATE SHDN
150k
XMT AUTOZERO
150k
AUTOZERO
–
AZ
+
TXENB
ADJUSTABLE
PA
50mV FILTER
–+
+
CAMP
–
ICL
33k
PB
CC 400µA
VPC
gm
140k
110k
33k
22k
22k
1.2V
BG1
1.2V BANDGAP
TSDB
1.2V
ADJUSTABLE
PB
12Ω
100Ω
TXENI
150k
MUX
CONTROL
PA
12Ω
100Ω
SHDN
3
TXEN
7
PCTL
6
BSEL
4
VPCA
9
VPCB
8
1758 BD
5
5 Page 
LTC1758-1/LTC1758-2
APPLICATIO S I FOR ATIO
This model (Figure 7) is being supplied to LTC users as an
aid to circuit designs. While the model reflects close
similarity to corresponding devices in low frequency AC
performance terms, its use is not suggested as a replace-
ment for breadboarding. Simulation should be used as a
forerunner or a supplement to traditional lab testing.
Users should note very carefully the following factors
regarding this model: Model performance in general will
reflect typical baseline specs for a given device, and
certain aspects of performance may not be modeled fully.
While reasonable care has been taken in the preparation,
we cannot be responsible for correct application on any
and all computer systems. Model users are hereby notified
that these models are supplied “as is”, with no direct or
implied responsibility on the part of LTC for their operation
within a customer circuit or system. Further, Linear Tech-
nology Corporation reserves the right to change these
models without prior notice.
In all cases, the current data sheet information is your final
design guideline, and is the only performance guarantee.
For further technical information, refer to individual device
data sheets. Your feedback and suggestions on this model
is appreciated.
Linear Technology Corporation hereby grants the users of
this model a nonexclusive, nontransferable license to use
this model under the following conditions:
The user agrees that this model is licensed from Linear
Technology and agrees that the model may be used,
loaned, given away or included in other model libraries as
long as this notice and the model in its entirety and
unchanged is included. No right to make derivative works
or modifications to the model is granted hereby. All such
rights are reserved.
This model is provided as is. Linear Technology makes no
warranty, either expressed or implied about the suitability
or fitness of this model for any particular purpose. In no
event will Linear Technology be liable for special, collat-
eral, incidental or consequential damages in connection
with or arising out of the use of this model. It should be
remembered that models are a simplification of the actual
circuit.
PCTL
CONTROL
AMPLIFER
BW1 ≅ 250kHz RF POWER AMP
+ VPCA/B
G1 G2
–
IFB LTC1758
RF
H1
H2
CONTROLLED
RF OUTPUT
POWER
RF DETECTOR
1758 F05
DIRECTIONAL
COUPLER
14dB to 20dB LOSS
Figure 5. Closed Loop Block Diagram
80
70
60
50
40
30
20
10
0
–10
–20
–30
–40
–50
–60
100
PHASE
RLOAD = 2k
CLOAD = 33pF
120
110
100
90
80
70
60
GAIN
50
40
30
20
10
0
–10
–20
1k 10k 100k 1M 10M
FREQUENCY (Hz)
1758 F06
Figure 6. SPICE Model Open Loop Gain and Phase
Characteristics from RF to VPCA, PCTL < 640mV
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC1758-2.PDF ] | |
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