LTC4251-1CS6-TR Linear Technology Corporation, LTC4251-1CS6-TR Datasheet
LTC4251-1CS6-TR
Related parts for LTC4251-1CS6-TR
LTC4251-1CS6-TR Summary of contents
Page 1
... The LTC4251 UV/OV thresholds are designed to match the standard telecom operating range of – 43V to – 75V. The LTC4251-1 UV/OV thresholds extend the operating range to encompass – 36V to – 72V. The LTC4251-2 implements a UV threshold of – 43V only. All parts are available in the 6-Pin SOT-23 package. ...
Page 2
... Current Out of Sense Pin (20µs Pulse) ............. –200mA Maximum Junction Temperature .......................... 125°C Operating Temperature Range LTC4251C/LTC4251-1C/LTC4251-2C ...... 0°C to 70°C LTC4251I/LTC4251-1I/LTC4251-2I .... – 40°C to 85°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ELECTRICAL CHARACTERISTICS ...
Page 3
... Timer On (Circuit Breaker, Sourcing), V Timer Off (Cooling Cycle, Sinking), V LTC4251/LTC4251-1 Note 2: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to V specified. Note 3: UV/ refers for the LTC4251- 1000 T = – ...
Page 4
... UV/ TIMER = – 0.15V SENSE GATE 105 –55 –35 – TEMPERATURE (°C) UV/ refers for the LTC4251-2. vs Undervoltage Lockout Hysteresis V vs Temperature LKH 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 125 –55 –35 – TEMPERATURE (°C) 425112 G05 ...
Page 5
... UV/ 100 TIMER = 0V GATE = HIGH T = 25°C A 1000 –1.5 –1.0 –0.5 0 0.5 1.0 (V – (V) SENSE EE LTC4251/LTC4251-1/ LTC4251-2 UV/ refers for the LTC4251-2. UV Threshold vs Temperature 3.375 LTC4251/LTC4251-2 3.275 V UVH 3.175 3.075 2.975 V UVL 2.875 2.775 125 –55 –35 – TEMPERATURE (°C) ...
Page 6
... TEMPERATURE (°C) 85 105 125 65 425112 G25 UV/ refers for the LTC4251-2. I (Circuit Breaking, Sourcing) TMR vs Temperature 280 260 240 220 200 180 125 –55 –35 – TEMPERATURE (°C) 425112 G23 ...
Page 7
... CTIO S UV/OV refers to the UV pin for the LTC4251-2. The OV comparator in the LTC4251-2 is disabled. All references in the text to overvoltage, OV, V SENSE (Pin 1): Circuit Breaker/Current Limit SENSE Pin. Load current is monitored by sense resistor R between SENSE and V , and controlled in three steps SENSE exceeds V ...
Page 8
... U OPERATIO Note that for simplicity, the following assumptions are made in the text. Firstly, UV/OV also means the UV pin of the LTC4251-2. Secondly, all overvoltage conditions and references to OV, V the OV comparator in this part is disabled. Hot Circuit Insertion When circuit boards are inserted into a live backplane, the supply bypass capacitors can draw huge transient currents from the power bus as they charge ...
Page 9
... TYP tant to set the timer delay so that, regardless of which SENSE GATE start-up mode is used, the start-up time is less than the TIMER delay time. If this condition is not met, the LTC4251 10Ω LTC4251-1/LTC4251-2 may shut down after one TIMER 4 delay ...
Page 10
... UV turning turning off resistor can turning off turning The UV and OV trip point ratio for LTC4251 is designed to match the standard telecom operating range of 43V to . LKH 75V. The LTC4251-2 implements a UV threshold of 43V ) the chip is enabled; only. ...
Page 11
... If more noise immunity is desired, add a 1nF to 10nF filter capacitor from UV/ The UV and OV trip point thresholds for the LTC4251-1 are designed to encompass the standard telecom operating range of –36V to –72V. A divider (R1, R2) is used to scale the supply voltage. Using R1 = 442k and R2 = 34.8k gives a typical operating range of 33 ...
Page 12
... EE conditions: in UVLO, during the initial timing cycle overvoltage condition, or when the LTC4251/LTC4251-1/ LTC4251-2 are latched off after a short-circuit. When GATE turns on, a 58µA current source charges the MOSFET gate and any associated external capacitance. V gate drive to no more than 14.5V. ...
Page 13
... U U APPLICATIO S I FOR ATIO capacitors. If LTC4251, LTC4251-1 or LTC4251-2s are used throughout, they respond by limiting the inrush cur- rent to a value of 100mV capacitors will recharge long before C SUPPLY RING SUPPLY RING OWING OWING TO MOSFET TO CURRENT –48RTN TURN-OFF OVERSHOOT 50V/DIV ...
Page 14
... V SENSE pins are strongly recommended. The drawing in Figure 6 illustrates the correct way of making connections between the LTC4251/LTC4251-1/LTC4251-2 and the sense resistor. PCB layout should be balanced and sym- metrical to minimize wiring errors. In addition, the PCB ...
Page 15
... In this example as shown in Figure 8, power is delivered through long connector pins whereas the UV/OV divider makes contact through a short pin. This ensures the power connections are firmly established before the LTC4251/ LTC4251-1/LTC4251-2 are activated. At time point 1, the power pins make contact and V ramps through V IN ...
Page 16
... LTC4251/LTC4251-1/ LTC4251 APPLICATIO S I FOR ATIO If the overvoltage glitch is long enough to deplete the load capacitor, a full start-up cycle may occur as shown be- tween time points 3 through GND-V EE UV/ TIMER GATE SENSE V OUT Figure 7. System Power-Up Timing (All Waveforms are Referenced to V ...
Page 17
... AND TIMER RESTARTS INITIAL TIMING CYCLE. OVLO TIMER CLEARS TMRH 5.8µA 230µA V TMRL 58µA START-UP CYCLE INITIAL TIMING CYCLE LTC4251/LTC4251-1/ LTC4251-2 or pulling TIMER below V UVLO . . CB , CHECK GATE < V AND SENSE < TMRL GATEL CB 5.8µA 5.8µA 58µA V ...
Page 18
... LTC4251/LTC4251-1/ LTC4251 APPLICATIO S I FOR ATIO The ramp duration is approximately 200µs. This feature reduces load current dl/dt at start-up. As illustrated in Figure 15, soft-start is initiated by a TIMER transition from 1 V OVHI UV/0V V TMRH TIMER 5.8µA GATE SENSE Figure 11. Overvoltage Timing (All Waveforms are Referenced to V ...
Page 19
... Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 0.95 REF 1.22 REF 1.50 – 1.75 2.80 BSC 1.4 MIN (NOTE 4) 0.95 BSC 0.80 – 0.90 1.00 MAX 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) LTC4251/LTC4251-1/ LTC4251-2 END OF INITIAL TIMING CYCLE 5.8µA V TMRH TIMER 230µA V TMRL ~V GS(th) GATE 58µA V ACL ...
Page 20
... SENSE Pin Limiting and Push-Reset at TIMER Pin R IN 10k 500mW 1µ UV/OV GATE C1 LTC4251-1 10nF 4 1 TIMER SENSE 220nF Figure 17. Power-Limited Circuit Breaker Application COMMENTS Negative High Voltage Supplies from –10V to –80V Supplies from 9V to 80V, Latched Off/Autoretry 3V to 16.5V, Overvoltage Protection up to 33V ± ...