LTC4252A-1CMS#TR Linear Technology, LTC4252A-1CMS#TR Datasheet

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... MOSFET drain voltage, keeping the MOSFET within its safe operating area (SOA). An adjustable soft- start circuit controls MOSFET inrush current at start-up. The LTC4252-1/LTC4252A-1 latch off after a circuit breaker fault times out. The LTC4252-2 provides automatic retry after a fault. The LTC4252A-1/LTC4252A-2 feature tight ± ...

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... LTC4252-2CMS8#TRPBF LTC4252-1IMS8 LTC4252-1IMS8#TRPBF LTC4252-2IMS8 LTC4252-2IMS8#TRPBF LEAD BASED FINISH TAPE AND REEL LTC4252-1CMS LTC4252-1CMS#TR LTC4252-2CMS LTC4252-2CMS#TR LTC4252A-1CMS LTC4252A-1CMS#TR LTC4252A-2CMS LTC4252A-2CMS#TR LTC4252-1IMS LTC4252-1IMS#TR LTC4252-2IMS LTC4252-2IMS#TR LTC4252A-1IMS LTC4252A-1IMS#TR LTC4252A-2IMS LTC4252A-2IMS#TR Consult LTC Marketing for parts specified with wider operating temperature ranges. For more information on lead free part marking, go to: ...

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... Low-to-High Transition ● ( ● for LTC4252A Only) ● 5.85 ● 5.25 Low-to-High Transition ● ● ( ● for LTC4252A Only) ● 4V 50mV SENSE ● LTC4252-1/-2 LTC4252A-1/-2 TYP MAX MIN TYP MAX 13 14.5 11.5 13 14.5 ...

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... DRN TMR Timer Off (Circuit Breaker/ Shutdown Cooling, Sinking TMR = Timer On (Circuit Breaker with DRN I = 50μA) DRN For PWRGD Status (MS Only (4V for LTC4252A) DRAIN I = 50μA DRN I = 1.6mA (MS Only 5mA (MS Only (Sourcing) (MS Only) PWRGD SS Pin Floating, V Ramps from SS ...

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... V (V) IN 425212 G02 Circuit Breaker Current Limit Voltage V vs Temperature –55 –35 – 105 25 TEMPERATURE (°C) 425212 G07 LTC4252A-1/LTC4252A Temperature 2mA 105 125 –55 –35 – TEMPERATURE (°C) Undervoltage Lockout V LKO vs Temperature 12.0 11.5 11.0 10.5 10.0 9.5 9.0 8.5 8.0 – ...

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... LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 TYPICAL PERFORMANCE CHARACTERISTICS V vs Temperature SS 2.40 2.35 2.30 2.25 2.20 2.15 2.10 2.05 2.00 –55 –35 – 105 125 TEMPERATURE (°C) 425212 G26 V vs Temperature OS 11.0 10.8 10.6 10.4 10.2 10.0 9.8 9.6 9.4 9.2 9.0 –55 –35 –15 ...

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... V TMRH 4.0 3.5 3.0 2.5 2.0 1.5 V TMRL 1.0 0.5 0 –55 –35 – 105 25 65 TEMPERATURE (°C) 425212 G19 LTC4252A-1/LTC4252A Temperature GATEL 0.8 UV/ TIMER = 0V 0.7 GATE THRESHOLD BEFORE RAMP-UP 0.6 0.5 0.4 0.3 0.2 0.1 0 –55 –35 – 105 TEMPERATURE (° ...

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... LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 TYPICAL PERFORMANCE CHARACTERISTICS I (Circuit Breaker, Sourcing) TMR vs Temperature 280 TIMER = 0μA DRN 260 240 220 200 180 –55 –35 – 105 TEMPERATURE (°C) 425212 G22 TMR DRN 10 1 0.1 0.001 0.01 0 (mA) DRN 425212 G33 V vs Temperature DRNL 2.60 FOR PWRGD STATUS (MS ONLY) 2 ...

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... SS pin voltage to 2.2V (50k resistor and 1.4V IN for the LTC4252A). This corresponds to an analog current limit SENSE voltage of 100mV (60mV for the LTC4252A). If the SS capacitor is omitted, the SS pin ramps up in about 180μs. The SS pin is pulled low under any of the following ...

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... V quickly pulls low and GATE is activated. If SENSE exceeds 50mV while GATE is high, a circuit breaker cycle begins with a 230μA pull-up current charging DRAIN is approximately 7V (6V for LTC4252A) dur- T ing this cycle, the timer pull-up has an additional current of 8 • I DRN reaches 4V, a 5.8μ ...

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... EE (2.5k *OV AND UV ARE TIED TOGETHER ON THE MS8 PACKAGE. OV AND UV ARE SEPARATE PINS ON THE MS PACKAGE ** ONLY AVAILABLE IN THE MS PACKAGE FOR COMPONENTS, CURRENT AND VOLTAGE WITH TWO VALUES, VALUES IN PARENTHESES REFER TO THE LTC4252A. VALUES WITHOUT PARENTHESES REFER TO THE LTC4252 LTC4252A-1/LTC4252A-2 – 2.385V V IN 58μ ...

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... MOSFET switch (see Figure 1). Both inrush control and short-circuit protection are provided by the MOSFET. A detailed schematic for the LTC4252A is shown in Figure 2. – 48V and –48RTN receive power through the longest con- nector pins and are the first to connect when the board is inserted ...

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... There are three distinct thresholds at SENSE: S 50mV for a timed circuit breaker function; 100mV for an analog current limit loop (60mV for the LTC4252A); and 200mV for a fast, feedforward comparator which limits peak current in the event of a catastrophic short-circuit. If, owing to an output overload, the voltage drop across R exceeds 50mV, TIMER sources 230μ ...

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... LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 APPLICATIONS INFORMATION SHUNT REGULATOR A fast responding shunt regulator clamps the V (VZ). Power is derived from –48RTN by an external current limiting resistor 1μF decoupling capacitor supply transients and contributes a short delay at start-up. To meet creepage requirements R may be split into two or IN more series connected units. This introduces a wider total ...

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... The R1-R2 divider values shown in Figure 2 set a standing current of slightly more than 100μA and define an impedance at UV/OV of 28kΩ. In most applications, 28kΩ impedance coupled with 324mV UV hysteresis makes the LTC4252A insensitive to noise. If more noise immunity is desired, add a 1nF to 10nF filter capacitor from UV/ The UV and OV pins can be used for a wider operat- ing range such as 35 ...

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... LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 APPLICATIONS INFORMATION conditions are met. A high-to-low transition in the UV comparator immediately shuts down the LTC4252, pulls the MOSFET gate low and resets the latched PWRGD high. Overvoltage conditions detected by the OV compara- tor will also pull GATE low, thereby shutting down the load ...

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... Unduly long soft-start intervals can exceed the MOSFET’s SOA rating if powering up into an active load floats, an internal current source ramps SS from 0V DRN to 2.2V for the LTC4252 1.4V for the LTC4252A in about 230μs. Connecting an external capacitor C from SS to ground modifies the ramp to approximate an RC response of: 80 ...

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... Each of these three measures the potential of SENSE relative to V SENSE exceeds 50mV, the CB comparator activates the 230μA TIMER pull-up. At 100mV (60mV for the LTC4252A), the ACL amplifier servos the MOSFET current and, at 200mV, the FCL comparator abruptly pulls GATE low in an attempt to bring the MOSFET current under control ...

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... The maximum current flowing in the DRAIN pin is given by calculated DRN(MAX) and C . The circuit breaker cur should be set to accommodate CB S SUPPLY(MIN) ) between ACL is 54mV to 66mV for LTC4252A) ACL 80mV This gives ACL 120mV = R S must be selected based on the T C • • SUPPLY(MAX) ...

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... This gauge is determined empirically with board level evaluation. ) SUMMARY OF DESIGN FLOW (13) To summarize the design flow, consider the application shown in Figure 2 with the LTC4252A. It was designed and for 80W. SUPPLY(MAX) Calculate the maximum load current: 80W/43V = 1.86A; allowing for 83% converter efficiency, I ...

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... TIMING WAVEFORMS System Power-Up Figure 9 details the timing waveforms for a typical power- up sequence in the case where a board is already installed in the backplane and system power is applied abruptly. At LTC4252A-1/LTC4252A-2 TRACK WIDTH W: 0.03" PER AMP COPPER 8000 6000 Figure 8. Making PCB Connections to the Sense Resistor ...

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... LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 APPLICATIONS INFORMATION V CLEARS V IN LKO 1 2 GND – (–48RTN) – (–48V) UV/ LKO IN TIMER GATE V GATEL SS SENSE V OUT DRAIN PWRGD Figure 9. System Power-Up Timing (All Waveforms Are Referenced time point 8, the load current falls and the SENSE voltage drops below V (t) ...

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... SS control level and the analog current limit loop activates. Between time points 6 and 8, the GATE voltage is servoed, the SENSE voltage is regulated at V (t) and soft-start limits the slew rate of the load ACL current. If the SENSE voltage (V SENSE LTC4252A-1/LTC4252A-2 , CHECK OV < GATE < SENSE < V UVHI OVHI GATEL CB ...

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... LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 APPLICATIONS INFORMATION Undervoltage Timing In Figure 11 when UV pin drops below V the LTC4252 shuts down with TIMER, SS and GATE all pulling low. If current has been flowing, the SENSE pin voltage decreases to zero as GATE collapses. When UV recovers and clears V (time point 2), an initial timer UVHI cycle begins followed by a GATE start-up cycle ...

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... Figure 12. Undervoltage Timing with an Overvoltage Glitch (All Waveforms Are Referenced OVERSHOOTS OVHI OV TIMER GATE V GATEL SS SENSE Figure 13. Overvoltage Timing (All Waveforms Are Referenced to V LTC4252A-1/LTC4252A-2 , SENSE < V GATEL CB AND TIMER ABORTS INITIAL TIMING CYCLE OVHI AND TIMER RESTARTS INITIAL TIMING CYCLE OVLO TIMER CLEARS V TMRL ...

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... LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 APPLICATIONS INFORMATION TMRH 5.8μA TIMER DRN GATE SS V ACL V CB SENSE V OUT DRAIN PWRGD CB FAULT (14a) Momentary Circuit-Breaker Fault Figure 14. Circuit-Breaker Timing Behavior (All Waveforms Are Referenced to V the V threshold, TIMER is discharged by 5.8μA. In TMRH Figure 14b, when TIMER exceeds V TMRH immediately and the LTC4252 shuts down ...

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... DRN 5.8μA TIMER V TMRL GATE SS SENSE V OUT DRAIN PWRGD CB FAULT Figure 16. Shutdown Cooling Timing Behavior of LTC4252-2 (All Waveforms Are Referenced to V LTC4252A-1/LTC4252A-2 SWITCH RESETS LATCHED TIMER SWITCH RELEASES 5.8μA V TMRH 5.8μA DRN V TMRL 58μA V – V ...

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... MOSFET can help T D prevent SOA damage in a low impedance fault condition. Soft-Start If the SS pin is not connected, this pin defaults to a linear voltage ramp, from 0V to 2.2V in about 180μs ( 1.4V in 230μs for the LTC4252A) at GATE start-up TMRH DRN ...

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... A soft-start voltage below V CB circuit breaker TIMER. Power Limit Circuit Breaker Figure 19 shows the LTC4252A power limit circuit breaking application. The SENSE pin is modulated by the board supply voltage The D1 Zener voltage, V SUPPLY is set to be the same as the low supply operating voltage 43V ...

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... INC † Circuit Breaker with Foldback Current Limit Figure 20 shows the LTC4252A in a foldback current limit application. When V is shorted to the –48V RTN supply, OUT current flows through resistors R4 and R5. This results in a voltage drop across R5 and a corresponding reduction ...

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... T SS SENSE V EE 0.68μ 68nF † **DIODES, INC RECOMMENDED FOR HARSH ENVIRONMENTS R IN 3× 1.8k 1/4W EACH † 1μF DDZ13B V IN LTC4252A PWRGD DRAIN 10 6 TIMER GATE SENSE V EE 0.68μ 68nF † RECOMMENDED FOR HARSH ENVIRONMENTS rises as current flows into R5 and R8 through resistors R3 and R6 ...

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... LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 APPLICATIONS INFORMATION –48RTN DIODE-OR CIRCUIT FOR CHANNEL A –48V A R IN2 3 × 1.8k IN SERIES 1/4W EACH C IN2 1μF FDV301N DIODE-OR CIRCUIT FOR CHANNEL B –48V B R IN3 3 × 1.8k IN SERIES 1/4W EACH C IN3 1μF FDV301N † **DIODES, INC RECOMMENDED FOR HARSH ENVIRONMENTS ...

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... C SS 68nF –48V LTC4252A-1/LTC4252A-2 the current flow. The sense voltage is lifted up and causes the fast comparator of LTC4252 to trip and pull the GATE low instantly. The channel A supply short will not cause Q3 of channel B diode-OR circuit to turn off. Similarly, when the channel B supply is shorted to the – ...

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... LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 PACKAGE DESCRIPTION 0.889 ± 0.127 (.035 ± .005) 5.23 3.20 – 3.45 (.206) (.126 – .136) MIN 0.42 ± 0.038 0.65 (.0165 ± .0015) (.0256) TYP BSC RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. ...

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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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 12, 14, 15, 30, 31, 32, 33 PAGE NUMBER 1, 36 ...

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... LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 TYPICAL APPLICATION –48RTN –48RTN (SHORT PIN) R1 402k 1% R2 32. 10nF –48V **DIODES, INC RELATED PARTS PART NUMBER DESCRIPTION LT1640AH/LT1640AL Negative High Voltage Hot Swap Controllers in SO-8 LT1641-1/LT1641-2 Positive High Voltage Hot Swap Controllers in SO-8 LTC1642 Fault Protected Hot Swap Controller ...