ltc3900 Linear Technology Corporation, ltc3900 Datasheet
ltc3900
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ltc3900 Summary of contents
Page 1
... MOSFETs and accepts pulse sychronization from the primary-side controller via a pulse transformer. = 4700pF L The LTC3900 incorporates a full range of protection for the external MOSFETs. A programmable timeout function is included that disables both drivers when the synchroniza- tion signal is missing or incorrect. Additionally, the chip ...
Page 2
... V = –5V IN SYNC V – (Note ±10V SYNC (Note 6) (Note –100mA OUT I = 100mA OUT (Note ORDER PART NUMBER 8 SYNC LTC3900ES8 7 TIMER GND 6 S8 PART 5 FG MARKING 3900 MIN TYP MAX UNITS ● 4 ● 4.1 4.5 0.5 ● 0 ● ...
Page 3
... Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC3900E is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature range are assured by design; characterization and correlation with statistical process controls. Note 3: All currents into device pins are positive ...
Page 4
... LTC3900 W U TYPICAL PERFOR A CE CHARACTERISTICS SYNC Negative Threshold vs Temperature –1 5V, 11V CC –1.1 –1.2 –1.3 –1.4 –1.5 –1.6 –1.7 –1.8 –50 – 100 125 TEMPERATURE (°C) 3900 G07 Propagation Delay vs C LOAD 120 T = 25° 110 CC 100 ...
Page 5
... R-C network to program the timeout period. The LTC3900 resets the timer at every negative transition of the SYNC input. If the SYNC signal is missing or incorrect, the LTC3900 pulls both CG and FG low once the TIMER pin goes above the timeout threshold. See the Timer section for more details on programming the timeout period. ...
Page 6
... CG to turn off, Q3 conducts. Current flows to the load through Q3, T1 and L goes low and T2 generates a positive pulse at the LTC3900 SYNC input. The LTC3900 forces FG to turn off and CG to turn on, Q4 conducts. Current continues to flow to the load through Q4 and L nization waveforms. ...
Page 7
... C . The SG signal stops switching and there VCC is no SYNC pulse to the LTC3900. The LTC3900 keeps one of the drivers turned on depending on the polarity of the last SYNC pulse. If the last SYNC pulse is positive, CG will remain high and the catch MOSFET, Q4 will stay on. The ...
Page 8
... TMR of the inductor negative peak current and MOSFET R voltage. This higher than 10.5mV, the LTC3900 will operate in discon tinuous current mode. Figure 6 shows the LTC3900 oper- ating in discontinuous current mode; the CG output goes low before the next negative SYNC pulse, as soon as the inductor current becomes negative ...
Page 9
... Add a series resistor, R and R , should be parallel sum of R CS3 the other end of R SYNC Input Figure 7 shows the external circuit for the LTC3900 SYNC input. With a selected type of pulse transformers, the values of the C an optimum SYNC pulse amplitude and width. A bigger } CS2 capacitor, C ...
Page 10
... B ohms), in series with the base of Q REG surpress high frequency oscillations depending on Q selection. The LTC3900 has an UVLO detector that pulls the drivers output low if V < 4.1V. The UVLO detector has 0. hysteresis to prevent chattering typical forward converter, the secondary-side circuits have no power until the primary-side controller starts operating ...
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... TYP (0.203 – 0.254) .016 – .050 (0.406 – 1.270) LTC3900 L1 C OUT Q2 Q3 100µF PH3230 PH3230 3x 10k 2x 2x LTC3900 10k GND CS 10k 4 2 – ...
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... Used for 20W to 500W Forward Converters For Regulated Auxiliary Output in Isolated DC/DC Converters 72V Operation, Synchronous Switch Output Regulates Two Secondary Outputs, Optocoupler Feedback Driver and Second Output Synchronous Driver Controller Similar Function to LTC3900, Used in Full-Bridge and Push-Pull Converter Optocoupler Driver with Overshoot Protection www.linear.com ● L1 2.4µ ...