LT1952-1 Linear Technology, LT1952-1 Datasheet
LT1952-1
Related parts for LT1952-1
LT1952-1 Summary of contents
Page 1
... The LT1952 is optimized for micropower bootstrap start-up from high input voltages. The LT1952-1 allows start-up from lower input voltages. Programmable slope compensation and OSC leading edge blanking allow optimization of loop bandwidth with a wide range of inductors and MOSFETs ...
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... T = 0.1μF , SD_V = 2V, BLANK = 121k, DELAY = 121k, I SEC PARAMETER PWM CONTROLLER Operational Input Voltage V Quiescent Current IN V Start-up Current (LT1952 Start-up Current (LT1952- Shutdown Current IN SD_V Threshold SEC SD_V Current SEC (ON) SD_V Current SEC (OFF) ...
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... –250μA (COMP 1V, SOUT Duty Cycle > 250μA (COMP) COMP = 2.5V COMP = 2.5V (Note 4) COMP = 2.5V (Note 4) COMP = 2.5V (OC = 100mV) COMP = 2.5V 1V 40k (Note 10) BLANK COMP = 2.5V 1V 120k BLANK LT1952/LT1952 REF REF MIN TYP MAX UNITS l 14.25 15. 8.75 9. 3.75 5 ...
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... LT1952/LT1952-1 ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are 0.1μF , SD_V = 2V, BLANK = 121k, DELAY = 121k, I SEC PARAMETER SOUT DRIVER SOUT Clamp Voltage SOUT Low Level SOUT High Level SOUT Active Pull-Off in Shutdown SOUT to OUT (Rise) DELAY (t DELAY V DELAY ...
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... TEMPERATURE (°C) 1952 G04 V Turn ON/OFF Voltage IN vs Temperature 18 16 LT1952 V TURN ON VOLTAGE LT1952 V TURN OFF VOLTAGE IN 8 LT1952 LT1952 100 125 –50 – TEMPERATURE (°C) 1952 G07 LT1952/LT1952-1 V Shutdown Current IN vs Temperature 500 V = 15V ...
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... LT1952/LT1952-1 TYPICAL PERFORMANCE CHARACTERISTICS COMP Source Current vs Temperature 12 COMP = 1.6V 10.0 7.5 CURRENT OUT OF PIN 5.0 – –25 TEMPERATURE (°C) I Maximum Threshold SENSE vs COMP 240 T = 25° ISENSE 200 160 120 OC THRESHOLD 0.5 1.0 1.5 2.0 COMP (V) I Maximum Threshold SENSE vs Duty Cycle (Programming ...
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... SEC R = 10k 2.20 DELAY = 1.32V SEC 2.08 1.96 = 1.98V SEC 1.84 = 2.64V SEC 1.72 1.60 2.08 100 200 300 f (kHz) OSC 1952 G23 LT1952/LT1952 SOUT Rise to OUT Rise DELAY vs R DELAY 240 T = 25°C A 160 80 0 125 75 100 120 R (k) DELAY 1952 G19 OUT: Max Duty Cycle CLAMP ...
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... V IN decoupled to ground. An internal undervoltage lockout threshold exists for V and 8.75V off for the LT1952. The LT1952-1 has lower undervoltage lockout thresholds set at 7.75V on and 6.5V off. SOUT (Pin 16): Switched Output in Phase with OUT Pin. Provides sync signal for control of secondary side FETs in forward converter applications requiring highly effi ...
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... RAMP 8μ 35μA 80% DC (VOLTAGE) ERROR AMPLIFIER + 1.23V – COMP GND Figure 2. Block Diagram LT1952/LT1952-1 0.8V (ACTIVE THRESHOLD) 0.45V (RESET THRESHOLD) 0.2V SOFT-START LATCH RESET: V > 14.25V (> 8.75V IF LATCH SET BY OC) IN AND SD_V > 1.32V SEC AND OC < 107mV AND SS_MAXDC < 0.45V ...
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... The LT1952/LT1952-1 are current mode synchronous PWM controllers optimized for control of the simplest forward converter topology—using only one primary MOSFET. The LT1952/LT1952-1 are ideal for 25W to 500W power systems where very high effi ciency and reliability, low complexity and cost are required in a small space. ...
Page 11
... A resistor divider from the application’s output voltage generates a voltage at the inverting FB input of the LT1952/ pin causes the SEC LT1952-1 error amplifi er (or to the input of an external is SEC optocoupler) and is compared to an accurate reference (1.23V for LT1952/LT1952-1). The error amplifi er output (COMP) defi ...
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... SEC The LT1952/LT1952-1 use turn-on voltage hysteresis at the V start-up (Figure 4). The LT1952/LT1952-1 monitor V voltage to allow part turn on at 14.25V (7.75V LT1952-1) and part turn off at 8.75V (6.5V LT1952-1). Low start-up pin. ). The R resistor chosen for non-synchronized SLOPE ...
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... MOSFET during gate rise time and some time thereafter. This noise can + 1.32V potentially exceed the OC and I LT1952/LT1952-1 to cause premature turn off of SOUT and OUT in addition to false trigger of soft-start. The LT1952/ LT1952-1 provide programmable leading edge blanking of the OC and I < V < ...
Page 14
... Xns X + 45ns Figure 6. Leading Edge Blank Timing Programming Current Limit (OC Pin) The LT1952/LT1952-1 use a precise 107mV sense threshold at the OC pin to detect overcurrent conditions in the converter and set a soft-start latch independent of duty cycle because it is not affected by slope compensation programmed at the I ...
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... The LT1952/LT1952-1 have an additional output SOUT which provides a ±50mA peak drive clamped to 12V. In applications requiring synchronous rectifi cation for high effi ciency, the LT1952/LT1952-1 SOUT provides a sync signal for secondary side control of the synchronous rectifi er MOSFETs (Figure 11). Timing delays through the converter can cause non-optimum control timing for the synchronous rectifi ...
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... The LT1952/LT1952-1 have built-in soft-start capability to provide low stress controlled start-up from a list of fault conditions that can occur in the application (see Figure 1 and Figure 10). The LT1952/LT1952-1 provide true PWM soft-start by using the SS_MAXDC pin to control soft-start timing. The proportional relationship between SS_MAXDC ...
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... SEC (C) OC < 107mV, and (D) SS_MAXDC < 0.45V (SS_MAXDC reset threshold) *V > 8.75V (6.5V LT1952- for latch reset if the latch IN was only set by overcurrent condition in (3) above. SS_MAXDC Discharge Timing It can be seen in Figure 10 that two types of discharge can occur for the SS_MAXDC pin. In timing (A) the fault that caused the soft-start event has been removed before SS_MAXDC falls to 0 ...
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... LT1952/LT1952-1 APPLICATIONS INFORMATION V (t) = SS_MAXDC(DC) (1 – give • (–1) • ln(1 – where SS_MAXDC voltage at time t SS SS_MAXDC(DC) = programmed DC voltage setting maximum duty cycle clamp = REF (Figure 11 CHARGE (Figure 11) SS Example (1) No Switching Period ...
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... SS the single switch forward converter topology. 95% Effi cient, 5V, Synchronous Forward Converter = 26.3k CHARGE The circuit in Figure 14 is based on the LT1952-1 to provide ) SS(ACTIVE) the simplest forward power converter circuit—using only –7 • (–1) • ln(1 – 0.8/1.84) one primary MOSFET. The SOUT pin of the LT1952-1 – ...
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... LOAD CURRENT (A) Figure 12. LT1952-Based Synchronous Forward Converter Effi ciency vs Load Current (For Circuit in Figure 14) 16 SOUT SOUT 5 SS_MAXDC 100k 22k 6 V REF 2 LT1952-1 FB 0.1μF 0.1μ OSC 115k 4 SYNC BLANK DELAY 9 40k Q1: PHM15NQ20 PHILIPS 48V OUT ...
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... Some ‘Bus Converter’ solutions run with a fi xed 50% duty cycle resulting in an output variation of 2-to-1 for applications with a 72V to 36V input range. The LT1952/LT1952-1 use an accurate wide programmable range Volt-Second clamp to initially program and then control power supply output voltage to typically ± ...
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... MOSFET controller (LTC3900) which results in high effi ciency synchronous rectifi cation. The LT1952/LT1952-1 use a precision current limit threshold at the OC pin combined with a soft-start hiccup mode to provide low stress output short-circuit protection. The maximum output current will vary only 10% over the full V range ...
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... Some bus converters use a switch duty cycle limit which causes output voltage variation of typically ±33% over a 2:1 input voltage range. The LT1952/LT1952-1 typically provide 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) ...
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... LT1952/LT1952-1 PACKAGE DESCRIPTION .254 MIN .0165 .0015 RECOMMENDED SOLDER PAD LAYOUT .007 – .0098 (0.178 – 0.249) NOTE: 1. CONTROLLING DIMENSION: INCHES 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE * DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" ...