lt4220 Linear Technology Corporation, lt4220 Datasheet
lt4220
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lt4220 Summary of contents
Page 1
... A select- able tracking mode allows dual supply tracking control for ramping the positive and negative supplies together. The LT4220 features foldback current limit and latches off both gates if either supply remains in current limit longer than an adjustable time period. The IC can be configured for automatic restart after a delay set by the same timer ...
Page 2
... V + SENSE ............................................. –0. – SENSE , SENSEK ....................... V PWRGD, FAULT ................................. –0. Operating Temperature Range LT4220C ........................................... LT4220I ....................................... – Storage Temperature Range ................. – 150 C Lead Temperature (Soldering, 10 sec).................. 300 C DC ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL PARAMETER V ...
Page 3
... TIMERUP I = 2mA 5mA 16.5V PWRGD I = 2mA 5mA 16.5V FAULT TRACK = 16. TRACK = V (Note 3) GATE + TRACK = V (Note 3) GATE – CC LT4220 MIN TYP MAX 0. –16.5V 0.015 0. –16.5V 0.05 0 –10 –15 –22 –43 –52 –61 –9 –13 – ...
Page 4
... LT4220 AC ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL PARAMETER + + t ON Low to GATE Low PHLON + + + t ON High to GATE High PLHON + + t FB Low to PWRGD Low PHLFB + + t FB High to PWRGD High PLHFB + – – Low to GATE Low PHLON – – – ...
Page 5
... VOLTAGE (V – – (V) GATE EE 4220 G08 TIMER Pull-Up Current (V) CC 4220 G11 LT4220 + GATE Pull-Up Current vs + GATE Voltage – SENSE CC V – SENSE ...
Page 6
... LT4220 W U TYPICAL PERFOR A CE CHARACTERISTICS + + FB and ON Threshold Voltage vs Temperature 1.241 1.240 1.239 1.238 1.237 1.236 1.235 –40 – TEMPERATURE ( C) 4220 G13 6 – – FB and ON Threshold Voltage vs Temperature –1.241 –1.240 –1.239 –1.238 –1.237 –1.236 – ...
Page 7
... A pull-down current. When the TIMER pin falls below 0.5V, the part is allowed to restart + if the ON internal fault latch—typically done by connecting the LT4220 – in the range – < 0V. To disable V PWRGD and foldback EE – ...
Page 8
... LT4220 CTIO S + FAULT pin to the ON pin, otherwise the part remains latched off. To disable the timeout circuit breaker, connect the TIMER pin to GND. GND (Pin 9): Supply Ground Pin. PWRGD (Pin 10): Open-Collector Output to GND. PWRGD goes to high impedance after the initial GATE ...
Page 9
... FAULT LATCH GATE ON UVLO V AND CC GOOD EE 10 PWRGD GATE GOOD LATCHES TOFF TRACK OFF LATCH LT4220 V CC CURRENT LIMIT 60 A FROM SENSE AMPS I LIM PUMP + V CC – – 53mV + TRACK – – ...
Page 10
... When circuit boards are inserted into a live backplane, the circuit board bypass capacitors can draw large peak currents from the backplane power bus as they charge up. The LT4220 is designed to turn on a board’s V dual supplies in a controlled manner, allowing the circuit board to be safely inserted or removed from a live backplane. The part provides supply tracking as well as undervoltage and overcurrent protection ...
Page 11
... Resistor dividers R9, R10 and R11, R12 provide a power good signal and control output voltage tracking when TRACK is enabled. Internal Supply Diodes The LT4220 contains two internal diodes which clamp V and V with respect to GND in the event either supply pin CC is floating ...
Page 12
... Capacitor C3 and resistor R8 prevent Q2 from momen- tarily turning on when the power pins first make contact. Without C3, capacitor C2 and near ground before the LT4220 could power up and pull the gate low. The minimum required value of C3 can be calculated by: C ...
Page 13
... TIMER pin starts EE ramping back to GND by the 3.3 A current sink. After the W U fault latch is set, the LT4220 can be restarted by pulling the + ON pin low after the TIMER pin falls below 0.5V. The LT4220 can also be restarted by cycling either supply beyond its UVLO. Otherwise the part remains latched off. ...
Page 14
... LT4220 U U APPLICATIO S I FOR ATIO Supply Tracking If the TRACK pin (Pin 7) is high the supply power-up tracking mode is enabled. This feature forces both sup- plies to reach their final value at the same time, during power-up and for faults that drive the output supplies to zero ...
Page 15
... TYP .015 .004 45 .053 – .068 (0.38 0.10) (1.351 – 1.727) 0 – 8 TYP .008 – .012 (0.203 – 0.305) LT4220 .189 – .196* (4.801 – 4.978) .009 (0.229 REF .150 – .157** (3.810 – 3.988) ...
Page 16
... FAX: (408) 434-0507 www.linear.com Q1 + POWER GOOD R SUB85N03- 10nF SENSE GATE CC 10 PWRGD + R10 LT4220 R12 5 – FB – R11 – – SENSEK SENSE GATE 10nF 100nF 10 R14 10 S – ...