LT1158 Linear Technology, LT1158 Datasheet
LT1158
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LT1158 Summary of contents
Page 1
... MOSFET. Higher start-up currents are allowed as long as the MOSFET V does not exceed 1.2V. By returning the fault output to the enable input, the LT1158 will automatically shut down in the event of a fault and retry when an internal pull-up current has recharged the enable capacitor. ...
Page 2
... Sense Voltages (Pins 11, 12)................... – Top Source Voltage (Pin 13).................... – Boost to Source Voltage (V16 – V13) ....... –0.3V to 20V Operating Temperature Range LT1158C ................................................ LT1158I ............................................ – Junction Temperature (Note 1) LT1158C .......................................................... 125 C LT1158I ........................................................... 150 C Storage Temperature Range ................ – 150 C Lead Temperature (Soldering, 10 sec ...
Page 3
... Bottom Gate Fall Time Pin 6 (+) Transition, Meas. V9 (Note 3) F The denotes specifications that apply over the full operating temperature range. Note calculated from the ambient temperature T J dissipation P according to the following formulas: D LT1158IN, LT1158CN C/ LT1158IS, LT1158CS 110 C/W) J ...
Page 4
... C = 10000pF GATE 250 200 150 C = 3000pF GATE 100 C = 1000pF GATE SUPPLY VOLTAGE (V) LT1158 G11 Input Thresholds 2.0 1.8 V(HIGH) 1.6 –40°C +25°C +85°C 1.4 –40°C +25°C +85°C 1.2 V(LOW) 1.0 0 SUPPLY VOLTAGE (V) LT1158 G06 ...
Page 5
... Pin 3 (Bias): Decouple point for the internal 2.6V bias generator. Pin 3 cannot have any external DC loading. Pin 4 (Enable): When left open, the LT1158 operates normally. Pulling pin 4 low holds both MOSFETs off regardless of the input state. Pin 5 (Fault): Open collector NPN output which turns on when V12 – ...
Page 6
... LT1158 U U FUNCTIONAL DIAGRA + V BOOST BIAS BIAS 3 GEN ENABLE 4 7.5V 2.7V – 1.2V FAULT 5 7. INPUT – R 1.4V GND CHG PUMP + V 15V LOGIC INPUT – 1.75V – 2.6V 1-SHOT R 1-SHOT 110mV + 12 S – 15V 9 – 1. GATE FB ...
Page 7
... In order to conserve power, the gate drivers only provide turn-on current for set by internal one-shot circuits. Each LT1158 driver can deliver 500mA for 1000nC of gate charge –– more than enough to turn on multiple MOSFETs in parallel. Once turned on, each gate is ...
Page 8
... When the above calculations result in a lower R is economically feasible with a single MOSFET, two or more MOSFETs can be paralleled. The MOSFETs will inherently share the currents according to their R ratio. The LT1158 top and bottom drivers can each drive vs. tempera- four power MOSFETs in parallel with only a small loss in DS(ON) ...
Page 9
... TOP The actual increase in supply current is slightly higher due to LT1158 switching losses and the fact that the gates are being charged to more than 10V. Supply current vs. switching frequency is given in the Typical Performance Characteristics. The LT1158 junction temperature can be estimated by using the equations given in Note 1 of the electrical characteristics ...
Page 10
... The worst case for the diode is during a short circuit, when V ducts the short-circuit current almost continuosly. Figure 3 shows the LT1158 used to synchronously drive a pair of power MOSFETs in a step-down regulator applica- tion, where the top MOSFET is the switch and the bottom MOSFET replaces the Schottky diode ...
Page 11
... Kelvin connection at the shunt. When the voltage across R LT1158 fault pin begins to conduct. By feeding the fault signal back to a control input of the PWM, the LT1158 will assume control of the duty cycle forming a true current mode loop to limit the output current: I ...
Page 12
... APPLICATIONS INFORMATION Low Current Shutdown The LT1158 may be shutdown to a current level of 2mA by pulling the enable pin 4 low. In this state both the top and bottom MOSFETs are actively held off against any tran- sients which might occur on the output during shutdown. ...
Page 13
... If Short-Circuit Protection is Not Required In applications which do not require the current sense LT1158 F08 capability of the LT1158, the sense pins 11 and 12 should both be connected to pin 13, and the fault pin 5 left open. The enable pin 4 may still be used to shut down the device. Note, however, that when unprotected the top MOSFET ...
Page 14
... DS I START This calculation gives the minimum current which could be delivered with the IRFZ34 at T ing the fault pin on the LT1158. If more start current is required, using an IRFZ44 (R increase short-circuit current remains at 5A. In order for the V ...
Page 15
... V OFF IN Figure 10. High Efficiency 3.3V Step-Down Switching Regulator (Requires No Heatsinks MOSFET. The LT1158 will then go into the automatic restart mode described in Self-Protection with Automatic Restart above. The time constant for an incandescent filament is tens of to set I at approxi- milliseconds, which means that t SC longer than in most other applications ...
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... L1: COILTRONICS CTX02-12171 KRL/BANTRY SL-1R010J 20V INPUT + 500 F IRFZ34 LOW ESR SHORT-CIRCUIT CURRENT = 6A 510k 20m + – 100 100 IRFZ44 510 1N4148 LT1431 OUT 15A + 330 F 6.3V AVX 4 LT1158 F11 +5V/4A OUTPUT + 1000 F LOW ESR LT1158 F12 ...
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... THE CMOS 555 IS USED AS A 25kHz TRIANGLE-WAVE OSCILLATOR DRIVING THE LT1158 INPUT PIN. THE D.C. LEVEL OF THE TRIANGLE WAVE IS SET BY THE POTENTIOMETER ON THE CMOS 555 SUPPLY PIN, AND ALLOW ADJUSTMENT OF THE LT1158 DUTY CYCLE FROM 0 TO 100%. Figure 14. Potentiometer-Adjusted Open Loop Motor Speed Control with Short-Circuit Protection ...
Page 18
... LT1158 U TYPICAL APPLICATIONS + 10 F 1N4148 STOP (FREE RUN PWM Figure 15. High Efficiency 6-Cell NiCd Protected Motor Drive LT1158 ENABLE FAULT INPUT 5V SHUTDOWN PWM CONTROLS LT1158 INPUTS 18 BAT85 1 16 BOOST DR BOOST GATE DR 0. BIAS T GATE ENABLE T SOURCE ...
Page 19
... ESR + R S 0.015 – 2.4k + 470 F LOW SIDE B: SHOWS ESR CURRENT-SENSING MOSFET CONNECTION – 2.4k Q4 Q1, Q3: IRF540 (STANDARD) IRC540 (SENSE FET) Q2, Q4: IRFZ44 D1, D2: BAT83 R : DALE TYPE LVR-3 S ULTRONIX RCS01 LT1158 F17a 5V ENABLE A 0.01 F 5.1k FAULT A INPUT A 150k ENABLE B 0.1 F FAULT B 1N4148 INPUT B 1158F17c 19 ...
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... TYP : 499-3977 12V + 1000 F IRCZ44 + – 12V MBR330 55W I : 10A 50ms SHUTDOWN t = 600ms RESTART LT1158 F18 0.770 (19.558) MAX 0.260 ± 0.010 0.398 – 0.413 (10.109 – 10.490) (NOTE 2) ...