LTC1757A-2EMS Linear Technology, LTC1757A-2EMS Datasheet
LTC1757A-2EMS
Specifications of LTC1757A-2EMS
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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 ...
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... 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 ...
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... LTC1757A-1/LTC1757A APPLICATIO S I FOR ATIO ...
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... 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. ...
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... 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 ...