LTC4212 LINER [Linear Technology], LTC4212 Datasheet
LTC4212
Available stocks
Related parts for LTC4212
LTC4212 Summary of contents
Page 1
... An internal high side switch driver controls the gate of an external N-channel MOSFET for supply voltages ranging from 2.5V to 16.5V. The LTC4212 provides soft- start and inrush current limiting during the start-up period. It features a power-up timeout circuit that discon- nects the system supply when the onboard supplies do not enter into regulation within an adjustable timeout period ...
Page 2
... TIMER, PGT, PGF ....................................– 0. Output Voltages GATE ............................... Internally Limited (Note 3) FAULT .................................................. – 0.3V to 17V Operating Temperature Range LTC4212C .............................................. LTC4212I ........................................... – Storage Temperature Range ................. – 150 C Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are T SYMBOL ...
Page 3
... V . Driving this pin to voltages beyond the clamp may damage the part lower GATE pin voltage is desired, use an external zener diode. The GATE capacitance must be < 0. maximum V Note 4: Guaranteed by design and not tested in production. LTC4212 MIN TYP MAX UNITS 1.20 1.236 1 ...
Page 4
... LTC4212 W U TYPICAL PERFOR A CE CHARACTERISTICS otherwise noted. Supply Current vs Supply Voltage 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0 SUPPLY VOLTAGE (V) 4212 G01 GATE Voltage vs Supply Voltage SUPPLY VOLTAGE (V) 4212 G06 V – Temperature GATE ...
Page 5
... V = 0mV TO 200mV STEP CB 600 500 V 400 V CC 300 V CC 200 V = 15V CC 100 0 18 –50 – TEMPERATURE ( C) LTC4212 Specifications are 5V, unless (SLOW COMP) vs Supply CB Voltage 125 SUPPLY VOLTAGE (V) ...
Page 6
... LTC4212 W U TYPICAL PERFOR A CE CHARACTERISTICS otherwise noted. Power Good Timeout vs Temperature 20.0 19.5 19.0 18.5 18.0 17.5 17.0 16.5 16.0 15.5 15.0 –50 – 100 125 25 75 TEMPERATURE ( C) 4212 G41 PGF and PGT Pin Current (Timer or Filter Off) vs Supply Voltage –50 – 100 125 ...
Page 7
... TEMPERATURE ( C) Turn-Off Time vs Supply Voltage 125 SUPPLY VOLTAGE (V) LTC4212 Specifications are 5V, unless A CC Circuit Breaker RESET Time vs Supply Voltage 200 180 160 140 120 100 100 ...
Page 8
... To disable the electronic circuit breaker, connect the V and SENSE pins together (Pin 9): This is the positive supply input to the LTC4212. The CC LTC4212 operates from 2.5V < V current is typically 1mA. An internal undervoltage lockout circuit disables the device until the voltage at V FAULT ...
Page 9
... GLITCH FILTER DELAY OR UVLO LOGIC VALID DISABLE GLITCH GLITCH FILTER 5 A COMP5 COMP8 – – REF REF M5 0.95V M8 0.65V 4 PGF 6 PGI LTC4212 . An external CC GATE – V (TYP) = 28V V (TYP) = 12V 0.2V CHARGE 10 A PUMP 200 START-UP ON LOW CURRENT GATE >10 s ...
Page 10
... TIMER t 1 236 . V • TIMER design aid, the LTC4212’s timer period as a function of the C using standard values from 3.3nF to 0.33 F TIMER is shown in Table 1. The C value is vital to ensure a proper start-up and TIMER CC reliable operation. This timing period should not be exces- sive as an output short can occur at start-up causing the external MOSFET to overheat ...
Page 11
... Once the circuit breaker is tripped, the LTC4212 is latched off and the board is disconnected from the system supply. The ON pin must be taken low for 120 s to reset the circuit breaker and then high to reconnect the board to the backplane supply ...
Page 12
... Table 3. t PGF to ground. If the PGI Soft-Start or Inrush Current Control The LTC4212 monitors the load current by sensing the voltage (V sense resistor (R , PGF SENSE pins. During the second timing cycle (see Normal Operating Sequence) a soft-start circuit turns on the external N-channel FET gradually to keep inrush currents in check ...
Page 13
... LOAD GATE The timing diagram of Figure 2 illustrates when the LTC4212’s electronic circuit breaker is armed. After the first timing cycle, the LTC4212’s FAST COMP is armed at Time Point 6. This ensures that the system is protected against a short-circuit condition during the second timing (7) ...
Page 14
... LTC4212 U OPERATIO CHECK FOR GATE < 0.2V CHECK FOR FAULT HIGH FAST COMP ARMED 34V REF TIMER 1ST TIMING CYCLE (C ) TIMER GATE DC/DC CONVERTER OUTPUT V CC FAULT PGT PGI (RST) PGF (RST) PGI (PGOOD) PGF (PGOOD) NORMAL POWER-UP SEQUENCE Figure 2 ...
Page 15
... When V rises above the UVLO threshold of 2.34V (Time CC Point 2), the LTC4212 waits for the ON pin to go high ( > 1.316V) and checks that the GATE is low (V before initiating the first timing cycle (Time Point 3). The first timing cycle begins with the TIMER pin rate given by Equation 1 ...
Page 16
... Points 12 to 14). After that, taking the ON pin high (Time Point 15) starts a new power-up sequence. Autoretry Sequence Once the circuit breaker trips, the LTC4212 can be config- ured to autoretry that is attempt to reconnect the backplane supply automatically. Both FAULT and ON pins are tied ...
Page 17
... V REF 2ND TIMING CYCLE (C ) TIMER SOFT-START ACTIVE V OUT < 200ms V OUT 0.95V 0.65V POWER GOOD TIME-OUT CYCLE (C ) PGT LTC4212 ON GOES LOW LOGIC RESET (200 A GATE PULLDOWN) CIRCUIT BREAKER RESET REF 1ST TIMING CYCLE (C TIMER ECB RESET SEQUENCE 4212 F03 ...
Page 18
... PGI PGF Figure 4. Power-Up with Overcurrent, Slow Comparator Trips the Circuit Breaker 18 Sense Resistor Considerations The fault current level at which the LTC4212’s internal electronic circuit breaker trips is determined by a sense above AUTO resistor connected between the LTC4212’s V pins and two separate trip points. The first trip point is set ...
Page 19
... PGI FAULT 5 GND PGT TIMER PGF TIMER PGT PGF 0.01 F 180nF 18pF Z1 = SMAJ10A (TVS) Figure 5. LTC4212 Autoretry Application 1.31V 0.455V V V REF 2ND 1ST TIMING TIMING CYCLE (C ) CYCLE (C TIMER SOFT-START ACTIVE > 50mV, > – V ...
Page 20
... SENSE pins are strongly recommended. The CC drawing in Figure 7 illustrates the correct way of making connections between the LTC4212 and the sense resistor. PCB layout should be balanced and symmetrical to mini- mize wiring errors. In addition, the PCB layout for the sense resistor should include good thermal management techniques for optimal sense resistor power dissipation ...
Page 21
... GS = TRIP(MAX) MOSFET must be higher than the gate overdrive voltage. Lower V LTC4212 if the GATE overdrive is clamped to a lower voltage. The circuit in Figure 8 illustrates the use of zener diodes to clamp the LTC4212’s GATE overdrive signal if lower voltage MOSFETs are used. ) must be evaluated TOL ...
Page 22
... FAULT and ON) passing through the card’s edge connector should be wired to short length pins or blades. PCB Connection Sense There are a number of ways to use the LTC4212’s ON pin to detect whether the printed circuit board has been fully seated in the backplane before the LTC4212 commences a start-up cycle. ...
Page 23
... U MS Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661) DETAIL “A” 0.254 (.010) 0 – 6 TYP GAUGE PLANE 0.53 0.152 (.021 .006) DETAIL “A” 0.18 (.007) LTC4212 MANUFACTURER ON Semiconductor = 455pF ON Semiconductor = 1130pF ISS ON Semiconductor = 1570pF ISS ON Semiconductor = 2600pF ISS 3.00 0.102 (.118 .004) ...
Page 24
... M1 SENSE 0.007 Si4410DY + 100nF SENSE GATE 20k LTC4212 10 6 PGI FAULT 5 GND TIMER PGT PGF TIMER PGT PGF 0.01 F 180nF 18pF COMMENTS Operates from 3V to 12V and Supports – 12V Operates from 2.7V to 12V Operates from – ...