LT1952 Linear Technology, LT1952 Datasheet
LT1952
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LT1952 Summary of contents
Page 1
... MOSFETs. The LT1952 can be programmed over a 100kHz to 500kHz frequency range and the part can be synchronized to an external clock. The error amplifier is a true op amp, allowing a wide range of compensation networks. The LT1952 is available in a small 16-pin SSOP package. , LTC and LT are registered trademarks of Linear Technology Corporation. L1 ...
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... V < 25V, OSC IN SS_MAXDC = 1.84V R Pin voltage OSC www.DataSheet4U.com U W ORDER PART TOP VIEW NUMBER 16 SOUT 15 V LT1952EGN IN 14 OUT LT1952IGN 13 PGND 12 DELAY PART 10 I MARKING SENSE 9 BLANK 1952E GN PACKAGE 1952I = 110°C/W, θ = 40°C 178k, SYNC = 0V, SS_MAXDC = V OSC = 15V, SOUT = open, unless otherwise specified ...
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... I = –20mA 12V, COMP = 2.5V, (GATE –200mA 12V, COMP = 2.5V, (GATE 5V, SD_V = 0V, OUT = 1V IN SEC LT1952 www.DataSheet4U.com = 178k, SYNC = 0V, SS_MAXDC = V REF = 15V, SOUT = open, unless otherwise IN MIN TYP MAX UNITS ● 1.201 1.226 1.250 –75 –200 MHz – ...
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... Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT1952IGN is guaranteed over the full –40°C to 125°C operating junction temperature range. Note 3: Rise and Fall times are measured at 10% and 90% levels. ...
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... Temperature TURN ON VOLTAGE TURN OFF VOLTAGE –50 – 100 125 TEMPERATURE (°C) 1952 G08 LT1952 www.DataSheet4U.com V Shutdown Current vs IN Temperature 500 V = 15V IN SD_V = 0V SEC 450 400 350 300 250 200 150 100 –50 – ...
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... LT1952 W U TYPICAL PERFOR A CE CHARACTERISTICS COMP Source Current vs Temperature 12 COMP = 1.6V 10.0 7.5 CURRENT OUT OF PIN 5.0 –50 – 100 TEMPERATURE (°C) 1952 G10 I Maximum Threshold vs SENSE COMP 240 T = 25° ISENSE 200 160 120 OC THRESHOLD 2.0 0 0.5 1.0 1.5 2.5 COMP (V) 1952 G13 ...
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... OSC (for OUT DC = 72%) 2. 25°C A SD_V = 1.32V SEC R = 10k 2.20 DELAY 2.08 1.96 1.84 1.72 1.60 100 200 300 400 500 f (kHz) OSC 1952 G24 LT1952 www.DataSheet4U.com t : SOUT Rise to OUT Rise vs DELAY R DELAY 200 T = 25°C A 160 120 100 120 140 160 20 R (k) ...
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... LT1952 CTIO S COMP (Pin 1): Output Pin of the Error Amplifier. The error amplifier amp, allowing various compensation networks to be connected between the COMP pin and FB pin for optimum transient response. The voltage on this pin corresponds to the peak current of the external FET. ...
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... SEC (TYPICAL 200kHz) OSC (LINEAR) (100 TO 500)kHz SLOPE COMP RAMP 8µ 35µA 80% DC (VOLTAGE) ERROR AMPLIFIER 0mV TO 220mV 1 8 COMP GND Figure 2. Block Diagram LT1952 www.DataSheet4U.com 0.8V (ACTIVE THRESHOLD) 0.45V (RESET THRESHOLD) 0.2V > 1.32V 1952 F01 V REF + >90% SOFT-START CONTROL – ±50mA ...
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... V pin. IN Output Drivers The LT1952 has two outputs, SOUT and OUT. The OUT pin provides a ±1A peak MOSFET gate drive clamped to 13V. The SOUT pin has a ±50mA peak drive clamped to 12V and provides sync signal timing for synchronous rectification control ...
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... A resistor divider from the application’s output voltage pin causes the SEC generates a voltage at the inverting FB input of the LT1952 is SEC error amplifier (or to the input of an external optocoupler) and is compared to an accurate reference (1.23V for LT1952) ...
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... I approximately 8µ duty cycle to 35µA at 80% duty cycle. Over-Current Detection and Soft-Start (OC Pin) An added feature to the LT1952 is a precise 100mV sense threshold at the OC pin used to detect over-current condi- tions in the converter and set a soft-start latch. The OC pin U ...
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... This noise can potentially exceed the OC and I cause premature turn off of SOUT and OUT in addition to false trigger of soft-start. The LT1952 provides program- LT1952 mable leading edge blanking of the OC and I parator outputs to avoid false current sensing during 1952 F04 MOSFET switching ...
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... Xns X + 45ns Figure 6. Leading Edge Blank Timing Programming Current Limit (OC Pin) The LT1952 uses a precise 100mV sense threshold at the OC pin to detect over-current conditions in the converter and set a soft-start latch independent of duty cycle because it is not affected by slope compensation pro- grammed at the I pin ...
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... The LT1952 has an additional output SOUT which pro- vides a ±50mA peak drive clamped to 12V. In applications requiring synchronous rectification for high efficiency, the LT1952 SOUT provides a sync signal for secondary side control of the synchronous rectifier MOSFETs (Figure11). Timing delays through the converter can cause non- optimum control timing for the synchronous rectifier MOSFETs ...
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... Programming Soft-Start Timing The LT1952 has built-in soft-start capability to provide low stress controlled startup from a list of fault conditions that can occur in the application (see Figure 1 and Figure 10). The LT1952 provides true PWM soft-start by using the SS_MAXDC pin to control soft-start timing. The propor- ...
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... Time For Maximum Duty Cycle Clamp within X% of Target Value The time for SS_MAXDC to charge to a given voltage V is found by re-arranging (t) = SS_MAXDC(DC) (1 – LT1952 www.DataSheet4U.com = 100k 0.1µF and assume 0.45V, –4 + (2.5 – 0.45)[(1/2 • 100k) – (1/35.7k)] –4 –4 + (2.05)(– ...
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... LT1952 U U APPLICATIO S I FOR ATIO to give • (–1) • ln(1 – V /SS_MAXDC(DC)) SS where SS_MAXDC voltage at time t SS SS_MAXDC(DC) = programmed DC voltage setting maximum duty cycle clamp = REF (Figure 11 • R CHARGE (Figure 11) SS Example (1) No Switching Period ...
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... SS forward converter topology. 95% Efficient, 5V, Synchronous Forward Converter = 26.3k The circuit in Figure 14 is based on the LT1952 to provide ) the simplest forward power converter circuit — using only one primary MOSFET. The SOUT pin of the LT1952 pro- –3 s vides a synchronous control signal for the LTC1698 lo- cated on the secondary ...
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... U U APPLICATIO S I FOR ATIO OUT f OSC LOAD CURRENT (A) Figure 12. LT1952-Based Synchronous Forward Converter Efficiency vs Load Current (For Circuit in Figure 14) 16 SOUT SOUT SD_V SEC 5 SS_MAXDC OUT 100k 22k REF SENSE 2 FB PGND LT1952 0.1µ ...
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... Some ‘Bus Converter’ solutions run with a fixed 50% duty cycle resulting in an output variation of 2-to-1 for applications with a 72V to 36V input range. The LT1952 uses an accurate wide programmable range Volt-Second clamp to initially program and then control power supply output voltage to typically ± ...
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... ALL CAPACITORS X7R, CERAMIC, TDK T2: COILCRAFT Figure 18. 36V to 72V, 3.3V at 40A Synchronous Forward Converter controlled hiccup mode. This allows a significant reduc- tion in power component sizing using the LT1952-based converter. Figure 17. LT1952-Based Synchronous Forward Converter Efficiency vs Load Current (For Circuit in Figure 18 PA0912.002 47k • ...
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... The LT1952 typically provides a ±10% output variation for the same input variation. Typical output tolerance is further improved for the LT1952 by inserting a resistor from the system input voltage to the SS_MAXDC pin (Rx in Figure 19). The LT1952 electrical specifications for the OUT Max Duty ...
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... LT1952 PACKAGE DESCRIPTIO .254 MIN .0165 ± .0015 RECOMMENDED SOLDER PAD LAYOUT .007 – .0098 (0.178 – 0.249) .016 – .050 (0.406 – 1.270) NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) 3. DRAWING NOT TO SCALE *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" ...