 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LTC1957-1EMS8 Datasheet(PDF) 7 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LTC1957-1EMS8 Datasheet(HTML) 7 Page - Linear Technology |
|
|
7 / 16 page  7 LTC1957-1/LTC1957-2 Modes of Operation The LTC1957-2 supports three operating modes: shut- down, autozero and enable. In shutdown mode (SHDN = Low) the part is disabled and supply currents will be reduced to <1 µA. VPCA and VPCB will be connected to ground via 100 Ω switches. In autozero mode (SHDN = High, TXEN = Low) VPCA and VPCB will remain connected to ground and the part will be in the autozero mode. The part must remain in autozero for at least 50 µs to allow for the autozero circuit to settle. In enable mode (SHDN = High, TXEN = High) the control loop and protection functions will be operational. When TXEN is switched high, acquisition will begin. The control amplifier will start to ramp the control voltage to the RF power amplifier. The RF amplifier will then start to turn on. The feedback signal from the directional coupler and the output power will be detected by the LTC1957-2 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. MODE SHDN TXEN OPERATION Shutdown Low Low Disabled Autozero High Low Autozero Enable High High Power Control cancellation over the normal 1/8 duty cycle associated with the GSM protocol as well as multislot protocols. The part must be in the autozero mode for at least 50 µs for autozero to settle to the correct value. Filter There is a 350kHz filter included in the PCTL path. Protection Features The RF power amplifier is overcurrent protected by an internal sense amplifier. The sense amplifier measures the voltage across an internal 0.050 Ω resistor to determine the RF power amplifier current. VPCA or VPCB is lowered as this supply current exceeds 2.2A, thereby regulating the current to about 2.25A. The regulated current limit is temperature compensated. The 0.050 Ω resistor and the current limit feature can be removed by connecting the PA directly to VIN. The RF power amplifier control voltage pins are overvolt- age protected. The VPC overvoltage clamp regulates VPCA or VPCB to 2.85V when the gain and PCTL input combina- tion attempts to exceed this voltage. The internal thermal shutdown circuit will disable the LTC1957-2 if the junction temperature exceeds approxi- mately 150 °C. The part will be enabled when the tempera- ture falls below 140 °C. APPLICATIONS INFORMATION SHDN BSEL TXEN NOTE 1: THE EXTERNAL DAC DRIVING THE PCTL PIN CAN BE ENABLED DURING AUTOZERO. THE AUTOZERO SYSTEM WILL CANCEL THE DAC TRANSIENT. THE DAC MUST BE SETTLED TO AN OFFSET ≤400mV BEFORE TXEN IS ASSERTED HIGH. PCTL VPCA VPCB SHUTDOWN AUTOZERO t1 tS ENABLE NOTE 1 1957 TD t2 START VOLTAGE START VOLTAGE tS: AUTOZERO SETTLING TIME, 50µs MINIMUM t1: BSEL CHANGE PRIOR TO TXEN, 200ns TYPICAL t2: BSEL CHANGE AFTER TXEN, 200ns TYPICAL t3: START OF RAMP AFTER TXEN IS ASSERTED HIGH, 1 µs MINIMUM, 10µs MAXIMUM t3 LTC1957-2 Timing Diagram |
Similar Part No. - LTC1957-1EMS8 |
|
Similar Description - LTC1957-1EMS8 |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
