LTC1421 LINER [Linear Technology], LTC1421 Datasheet
LTC1421
Available stocks
Related parts for LTC1421
LTC1421 Summary of contents
Page 1
... The power-on reset input can be used to cycle the board power or clear the circuit breaker. The trip point of the ground sense comparator is set at 0.1V for LTC1421 and 2.5V for LTC1421-2.5. The LTC1421/LTC1421-2.5 are available in 24-pin SO and SSOP packages. 0. ...
Page 2
... OUTLO FB = Floating FB = GND ) OUTLO FB = Floating FB = GND CCLO – CCLO SETLO CB CCHI LTC1421 (Note 3) LTC1421-2.5 (Note ORDER PART TOP VIEW NUMBER 24 AUXV CCLO LTC1421CG 22 SETLO LTC1421CSW 21 GATELO LTC1421-2.5CG 20 V OUTLO LTC1421-2.5CSW 19 ...
Page 3
... Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: All currents into device pins are positive; all currents out of device pins are negative. All voltages are reference to ground unless otherwise specified. LTC1421/LTC1421-2 12V 5V unless otherwise noted (Note 2). ...
Page 4
... LTC1421/LTC1421-2 TYPICAL PERFORMANCE CHARACTERISTICS Reference Voltage vs Temperature 1.238 CCLO V = 12V CCHI 1.236 1.234 1.232 1.230 1.228 1.226 1.224 – 50 – 100 125 TEMPERATURE ( C) 1421 G01 GATELO Voltage vs V Voltage CCLO 12V CCHI ...
Page 5
... Ground. CPON is pulled high when the internal charge pumps for GATELO and GATEHI are turned on. CPON is pulled low when the charge pumps are turned off. The pin . can be used to control an external MOSFET for a – OUTHI – 12V supply. LTC1421/LTC1421-2.5 I Supply Current CCLO vs V Voltage CCLO ...
Page 6
... LTC1421/LTC1421-2 PIN FUNCTIONS RAMP (Pin 10): Analog Power-Up Ramp Control Pin. By connecting an external capacitor between the RAMP and GATEHI, a positive linear voltage ramp on GATEHI and GATELO is generated on power-up with a slope equal to 20 A/C RAMP. FB (Pin 11): Analog Feedback Input used to set the reset threshold voltage on V ...
Page 7
... CCHI AUXV + + CC 50mV – – CP1 CP2 UNDERVOLTAGE LOCKOUT DIGITAL CONTROL – SETLO CCLO FAULT CPON PWRGD RESET POR 1421 F01 t 6 LTC1421/LTC1421-2 GATELO RAMP GATEHI V V OUTHI OUTLO CHARGE PUMP N2 N1 CP3 + + – 73. – TRIP CP4 71.5k FB – ...
Page 8
... At the same time, the system data bus can be disrupted when the board’s data pins make or break connection. The LTC1421 is designed to turn a board’s supply voltages on and off in a controlled manner, allowing the board to be safely inserted or removed from a live backplane. The chip also provides a disable signal for the board’ ...
Page 9
... U U APPLICATIONS INFORMATION PWRGD and RESET The LTC1421 uses a 1.232V bandgap reference, internal resistive divider and a precision voltage comparator to monitor V (Figure 6). OUTLO The reset threshold voltage for V OUTLO the FB pin connection as summarized in Table 1. V CCLO 20 A COMP1 PWRGD V CCLO 20 A RESET RESET 1 ...
Page 10
... OUTLO drops below the new threshold, OUTLO LTC1421 16 73.5k COMP1 20 A 71.5k 11 – 26. COMP2 13 + RESET TIMING 14 – 8 1.232V 1421 F08d Figure 8d. Reset LTC1421 16 73.5k COMP1 20 A 71.5k 11 – 26. COMP2 13 + RESET TIMING 14 – 8 1.232V 1421 F08e – 12V 5k 12V 102k 1% 38.3k 1% 12V 10k 5% 13 ...
Page 11
... When a short circuit occurs on the board possible to draw enough current to cause the backplane supply voltage to collapse. If the input supply voltage collapses to a low enough voltage and the LTC1421 gate drive circuitry is unable to shut off the N-channel pass transistors, the system might freeze permanent short condition. ...
Page 12
... If the R DS(ON) drop across the transistor might cause the output voltage to trip the reset circuit. Table 2 lists the transistors that are recommended for use with the LTC1421. Table 2. N-Channel Selection Guide CURRENT PART LEVEL (A) ...
Page 13
... The switch inputs and outputs do not have a parasitic diode back to V and have very low capacitance. CC The LTC1421 is designed to work directly with the QuickSwitch bus switch as shown in Figure 13. The DISABLE signal is connected to the enable pins of the QS3384, and each switch is placed in series with a data bus signal ...
Page 14
... sequence will begin automatically. The trip point poten- tial for LTC1421 is set at 0.1V and 2.5V for LTC1421-2.5. In applications, where either V forced above 100mV before power-up, the LTC1421-2.5 should be used. This could occur when leakage through the body diode of the logic chips keeps V ...
Page 15
... When V threshold, the PWRGD signal is pulled high (time point 8). After a 200ms delay, RESET is pulled high and DISABLE goes low 20ms 20ms Figure 16. Circuit Breaker Timing LTC1421/LTC1421-2.5 and V OUTHI and V ramp OUTHI OUTLO has exceeded its reset OUTLO 7 8 ...
Page 16
... LTC1421/LTC1421-2 APPLICATIONS INFORMATION Board Removal Timing When the board is removed from the host, the sequence happens in reverse (Figure 17). Since CON1 and CON2 are the shortest pins, they break connection first and are internally pulled high (time point 1). The charge pumps are turned off, CPON is pulled low ...
Page 17
... POWERGOOD signal. The FAULT signal is also moni- tored to determine that the circuit breaker has tripped. – 48V and 24V Applications The LTC1421 may be used in – 48V applications as shown in Figure 19. The LTC1421 provides the hot insertion protection, while the 5V supply is generated by a power R1 0 ...
Page 18
... W U Figure 23 shows how to use the LTC1421 with a 5V supply and an LTC1430CS8 synchronous step-down switching regulator to generate 3.3V output 10A for micro- processors. Resistors R4, R8 and R9 set the turn-on voltage at 4.8V and the turn-off at 4.25V. Pushbutton switch S1 provides users a way to reset the output while S2 is used to soft-reset the microprocessor only ...
Page 19
... U U APPLICATIONS INFORMATION W U CONNECTOR STAGGERED LTC1421/LTC1421-2.5 19 ...
Page 20
... Figure 21. – 48V to 5V Hot Swappable Supply Q1 IRFR9110 + R2 C3 15k 2.2 F 1/8W 25V 56k 300 10 1/8W 1/ MPSA06 13 14 LTC1421 10A + + 10k 4.5k VICOR 100 F VI-J30-CY – – GATE IN 300 1N4148 4N25 0.1 F 100 ...
Page 21
... U U APPLICATIONS INFORMATION W U CONNECTOR STAGGERED LTC1421/LTC1421-2.5 21 ...
Page 22
... R6 C3 15k 0.47 F 1/8W IRF530 Figure 24. 5V and – 48V to 12V Hot Swappable Supply R1 0.005 Q1 1/2W MTB50N06E 1k 12 100 Q2 VN2222 LTC1421 2200 F R7 16V 1k 1/ +IN +OUT + + C5 ASTRODYNE 220 F ASD10-48D12 100V 2 5 –IN – OUT ...
Page 23
... SW Package 24-Lead Plastic Small Outline (Wide 0.300) (LTC DWG # 05-08-1620) 0.037 – 0.045 (0.940 – 1.143) 0.014 – 0.019 (0.356 – 0.482) 0.004 – 0.012 TYP (0.102 – 0.305) LTC1421/LTC1421-2 2200 F 16V 2200 F 16V ...
Page 24
... Q1 IRF7413 R12 0.22 F 24V 10 R13 11 5. LTC1421 20k MOTHERBOARD OR BACKPLANE Figure 27. PCI Power Controller COMMENTS Short-Circuit Protection and Micropower Standby Operation Inrush Current Limited, Built-In 2A Short-Circuit Protection PCI CONNECTOR 12V 3.3A CIRCUIT BREAKER R3 0.005 5% Q4 ...