LTC1757A-2EMS Linear Technology, LTC1757A-2EMS Datasheet

IC CTRLR RF POWER DUAL 10MSOP

LTC1757A-2EMS

Manufacturer Part Number
LTC1757A-2EMS
Description
IC CTRLR RF POWER DUAL 10MSOP
Manufacturer
Linear Technology
Datasheet

Specifications of LTC1757A-2EMS

Rf Type
Cellular, GSM, PCS, Wireless Modem, TDMA
Frequency
850MHz ~ 2GHz
Features
Dual Output
Package / Case
10-MSOP, Micro10™, 10-uMAX, 10-uSOP
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant

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Company
Part Number
Manufacturer
Quantity
Price
Part Number:
LTC1757A-2EMS
Manufacturer:
LT
Quantity:
10 000
Part Number:
LTC1757A-2EMS
Manufacturer:
LT
Quantity:
20 000
Part Number:
LTC1757A-2EMS#TR
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FEATURES
TYPICAL APPLICATIO
APPLICATIO S
, LTC and LT are registered trademarks of Linear Technology Corporation.
Single/Dual Band GSM Cellular Telephones
PCS Devices
Wireless Data Modems
TDMA Cellular Telephones
Dual Band RF Power Amplifier Control (LTC1757A-2)
Improved Internal Schottky Diode Detector
Wide Input Frequency Range: 850MHz to 2GHz
Autozero Cancels Initial Offsets and Temperature
Dependent Offset Errors
Wide V
Direct Connection to Battery
RF Output Power Set by External DAC
Fast Acquire After Transmit Enable
Internal Frequency Compensation
Rail-to-Rail Power Control Outputs
RF PA Supply Current Limiting
Battery Overvoltage Protection
Power Control Signal Overvoltage Protection
Low Operating Current: 1mA
Very Low Shutdown Current: < 1 A
Available in a 8-Pin MSOP Package (LTC1757A-1)
and 10-Pin MSOP (LTC1757A-2)
IN
Range of 2.7V to 6V Allows
U
68
V
IN
Li-Ion
33pF
SHDN
BSEL
1
2
3
4
5
U
LTC1757A-2 Dual Band Cellular Telephone Transmitter
V
RF
SHDN
BSEL
GND
IN
LTC1757A-2
DAC
TXEN
PCTL
V
V
V
PCA
PCB
CC
10
9
8
7
6
TXEN
1.8GHz /1.9GHz
900MHz
DESCRIPTIO
The LTC
RF power amplifiers operating in the 850MHz to 2GHz
range. The LTC1757A is pin compatible with the LTC1757
but has improved RF detection range. The input voltage
range is optimized for operation from a single lithium-ion
cell or 3 NiMH. Several functions required for RF power
control and protection are integrated in one small 10-pin
MSOP package, thereby minimizing PCB area.
The LTC1757A-1 is a single output RF power controller
that is identical in performance to the LTC1757A-2 except
that one output (V
be used to drive a single RF channel 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 voltage and 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 < 1 A.
RF PA
RF PA
®
1757A-2 is a dual band RF power controller for
LTC1757A-1/LTC1757A-2
RF Power Controllers
DIRECTIONAL
PCA
COUPLER
U
) is provided. The LTC1757A-1 can
Single/Dual Band
50
DIPLEXER
1757A TA01
1

Related parts for LTC1757A-2EMS

LTC1757A-2EMS Summary of contents

Page 1

... MSOP package, thereby minimizing PCB area. The LTC1757A single output RF power controller that is identical in performance to the LTC1757A-2 except that one output (V be used to drive a single RF channel or dual channel module with integral multiplexer. This part is available in an 8-pin MSOP package ...

Page 2

... VPCA VPCB PCA 100pF (Note 5) LOAD = 400 (Note 9) LOAD = 100pF (Note 3) LOAD = 2V Step PCTL = 100pF (Note 10) LOAD ORDER PART NUMBER TOP VIEW LTC1757A-2EMS 9 V PCA 8 V PCB 7 TXEN 6 PCTL MS10 PART MARKING = 250 C/W LTPM JA MIN TYP MAX 2 0.9 1 ...

Page 3

... BSEL Timing Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC1757A-1 and LTC1757A-2 are guaranteed to meet performance specifications from Specifications over the – operating temperature range are assured by design, characterization and correlation with statistical process controls. ...

Page 4

... When TXEN is low and SHDN is high the part is in the autozero mode. This input has an internal 150k resistor to ground. V (Pin 8): (LTC1757A-2 Only) Power Control Voltage PCB Output. This pin drives an external RF power amplifier power control pin. The maximum load capacitance is 100pF ...

Page 5

... DIPLEXER 900MHz RF PA Li-Ion AUTOZERO – 50mV – + 6pF ICL + 33k RFDET – 16.7k 33k 1.2V 33k 600mV XMT AUTOZERO 150k TXEN PCTL 7 6 LTC1757A-1/LTC1757A 1.8GHz 50 TXENB PA + ADJ – CAMP – 400 A 140k VPC g 110k m 1.2V OVP g m 173k V IN 54.5k 12 ...

Page 6

... V a 1.8GHz/1.9GHz channel. PCB BSEL must be established before the part is enabled. The LTC1757A-1 can be used to drive a single RF channel or dual channel module with integral multiplexer. Control Amplifier The control amplifier supplies the power control voltage to the RF power amplifier. A portion (typically – 19dB for low frequencies and – ...

Page 7

... The feedback voltage from the directional coupler and the PCA PCB output power will be detected by the LTC1757A-2 at the RF pin. The loop closes and the amplifier output tracks the DAC voltage ramping at PCTL. The RF power output will then follow the programmed power profile from the DAC. ...

Page 8

... RF pin directional coupler is used recommended that an external 68 termination resistor be connected between the RF coupling capacitor (33pF), and ground at the side connected to the directional coupler. If the termination is placed at the LTC1757A RF pin, then the 68 resistor must be connected to V the detector is referenced Termination compo- IN nents should be placed adjacent to the LTC1757A ...

Page 9

... RC time constants. Another factor that affects power ramp sidebands is the DAC signal to PCTL. The bandwidth of the LTC1757A is not low enough to adequately filter out steps associated with the DAC. If the baseband chip does not have an internal filter recommended that a 2-stage external filter be placed between the DAC output and the PCTL pin ...

Page 10

... Loop voltage losses supplied by the directional coupler will improve phase margin. The larger the directional coupler loss the more stable the loop will become. How- ever, larger losses reduce the RF signal to the LTC1757A and detector performance may be degraded at low power levels. (See RF Detector Characteristics.) ...

Page 11

... The phase margin degradation, due to external and internal pole combinations, is difficult to determine since complex poles are present. Gain peaking may occur, resulting in higher bandwidth and lower phase margin than predicted from the open loop Bode plot. A low frequency AC SPICE model of the LTC1757A power ...

Page 12

... VPCTLO, VRF, Adjust EFB gain to reflect external gain, currently set at 3X** *EFB RF 0 VPCA VIN 3 *VIN VIN *VPCTLO PCTL **Open loop connections, comment-out EFB, VIN and VPCTLO** VPCTLO PCTL VRF **Add AC statement and print statement as required** .AC DEC 50 100 1E7 .END Figure 8. LTC1757A Low Frequency AC SPICE Model ...

Page 13

... 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. LTC1757A-1/LTC1757A-2 13 ...

Page 14

... LTC1757A-1/LTC1757A APPLICATIO S I FOR ATIO ...

Page 15

... Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. LTC1757A-1/LTC1757A-2 U Dimensions in inches (millimeters) unless otherwise noted. ...

Page 16

... LTC1757A-1/LTC1757A-2 U TYPICAL APPLICATIO 68 33pF Li-Ion 3 SHDN 4 Using the LTC1757A Dual Band Cellular Telephone Transmitter Without Current Limiting 68 33pF LTC1757A Li-Ion RF 3 SHDN SHDN 4 GND DAC RELATED PARTS PART NUMBER DESCRIPTION LTC1261 Regulated Inductorless Voltage Inverter LTC1550/LTC1551 Low Noise Inductorless Voltage Inverter LTC1555L-1 ...

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