LT4256-1 LINER [Linear Technology], LT4256-1 Datasheet
LT4256-1
Available stocks
Related parts for LT4256-1
LT4256-1 Summary of contents
Page 1
... N-channel MOSFET shuts off and the PWRGD output asserts low. The LT4256-2 automatically restarts after a time-out delay. The LT4256-1 latches off until the UV pin is cycled low. The PWRGD output indicates when the output voltage rises above a programmed level. An external resistor string from V protection ...
Page 2
... FB High-to-Low Transition FB Low-to-High Transition I = 1.6mA 5mA 80V PWRGD 10nF TIMER U W ORDER PART NUMBER LT4256-1CS8 TOP VIEW LT4256-1IS8 LT4256-2CS8 7 SENSE LT4256-2IS8 6 GATE TIMER 5 S8 PART MARKING S8 PACKAGE 42561 8-LEAD PLASTIC SO 42561I = 125 C, = 110 C/W JA 42562 42562I ...
Page 3
... –50 – 100 TEMPERATURE ( C) 4256 G02 PWRGD Thresholds vs Temperature 4.5 L-H THRESHOLD 4.4 4.3 4.2 4.1 H-L THRESHOLD 4.0 3.9 – 100 –25 TEMPERATURE ( C) 4256 G05 LT4256-1/LT4256-2 MIN TYP MAX UNITS 1 0 unless 3.5 3.0 2.5 2.0 1.5 1.0 0 ...
Page 4
... LT4256-1/LT4256 TYPICAL PERFOR A CE CHARACTERISTICS otherwise noted. GATE Pin Pull-Up Current vs Temperature 0 –5 –10 –15 –20 –25 –30 –35 –40 –50 – 100 TEMPERATURE ( C) 4256 G07 V – V Voltage GATE CC vs Temperature 18V 12V ...
Page 5
... FB Pin Current vs FB Pin Voltage 0.2 0.1 0 –0.1 –0.2 –0.3 –0 Gate Pull-Down Capability vs V Below Minimum Operating Voltage (V) FB 4256 G15 LT4256-1/LT4256-2 Specifications are unless (V) CC 4256 G16 425612f 5 ...
Page 6
... A pull-down current. When TIMER falls below 0.65V (typ), GATE turns on again for the LT4256-2. UV must be cycled low after TIMER has discharged below 0.65V (typ) to reset the LT4256- not cycled low (LT4256-1), GATE remains latched off and TIMER is discharged to near GND. Under an output short-circuit condition, the LT4256-2 cycles on and off with a 3% duty cycle ...
Page 7
... REF GEN – INTERNAL + 9.8V + 0.65V TIMER LOW – + TIMER HIGH – 4.65V SENSE 7 – CURRENT 14mV ~ 55mV LIMIT + + FOLDBACK – UV – 4V LOGIC UV + LT4256-1/LT4256-2 CHARGE PUMP AND 6 GATE GATE DRIVER + 3 PWRGD 4V – 118 A 5 TIMER 4256 BD GND 425612f 7 ...
Page 8
... The transient currents can permanently damage the con- nector pins and glitch the system supply, causing other boards in the system to reset. The LT4256-1/LT4256-2 are designed to turn on a board’s supply voltage in a controlled manner, allowing the board to be safely inserted or removed from a live backplane. The ...
Page 9
... When the FB voltage goes above the low-to-high V threshold, PWRGD goes high. Undervoltage Detection The LT4256-1/LT4256-2 uses UV to monitor the V voltage to determine when it is safe to turn on the load and allow the user the greatest flexibility for setting the thresh- old. Any time that UV goes below 3.6V, GATE will be pulled low until UV goes above 4V again ...
Page 10
... FB. If the LT4256-1/LT4256-2 go into current limit when the voltage 0V, the current limit circuit drives the GATE pin to force a constant 14mV drop across the sense resistor ...
Page 11
... The drop across the sense resistor is held at 55mV as the timer ramps up. Once TIMER reaches its shutdown threshold (4.65V typically), the circuit latches off. The LT4256-1 latches off after a current limit fault. After the LT4256-1 latches off, the part may be commanded OUT ...
Page 12
... C3 0.1 F GND Power Good Detection The LT4256-1/LT4256-2 includes a comparator for moni- toring the output voltage. The output voltage is sensed through the FB pin via an external resistor string. The comparator’s output (PWRGD open collector ca- pable of operating from a pull-up as high as 80V. ...
Page 13
... LT4256-1/LT4256-2 have been designed to allow for some ringing below ground. However, if the applica- tion is such that V ground, damage may occur to the LT4256-1 and an external diode from ground (anode must be added to the circuit as shown in Figure 14 (it is critical that the reverse breakdown voltage of the diode be higher than the highest expected V and GND ...
Page 14
... R5 Q1 0.033 IRF530 D2 SMAT70A SENSE CC R6 64. GATE R7 LT4256-1/ 100 R2 LT4256-2 8.06k C1 10nF TIMER PWRGD C2 GND UV = 36V 33nF 4 PWRGD = 40V circuit) is recommended. The minimum trace width for 1oz copper foil is 0.02" per amp to make sure the trace stays at a reasonable temperature. 0.03" ...
Page 15
... TYP .016 – .050 .014 – .019 (0.406 – 1.270) (0.355 – 0.483) TYP INCHES (MILLIMETERS) LT4256-1/LT4256-2 .189 – .197 (4.801 – 5.004) NOTE .150 – .157 (3.810 – 3.988) NOTE 3 ...
Page 16
... 0.033 IRF530 D2 SMAT70A SENSE 64. GATE R7 LT4256-1/ 100 R2 LT4256-2 8.06k C1 10nF TIMER PWRGD C2 GND UV = 36V 33nF 4 PWRGD = 40V COMMENTS 9V to 80V Operation, Active Current Limit, Autoretry/Latchoff Floating Supply from –15V, Active Current Limiting, Fast Circuit Breaker Floating Supply from – ...