LT3750A AD | Alldatasheet
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Rev. 0For more information www.analog.com Document Feedback TYPICAL APPLICATION FEATURES DESCRIPTION Capacitor Charger Controller The LT®3750A is a flyback converter designed to rapidly charge large capacitors to a user-adjustable target volt- age. A patented boundary mode control scheme* mini - mizes transition losses and reduces transformer size. The transformer turns ratio and two external resistors easily adjust the output voltage.* A low 78mV current sense accurately limits peak switch current and also helps to maximize efficiency. With a wide input voltage range, the LT3750A can operate from a variety of power sources. A typical application can charge a 100µF capacitor to 300V in less than 300ms. The CHARGE pin gives full control of the LT3750A to the user. The DONE pin indicates when the capacitor has reached its programmed value and the part has stopped charging.
APPLICATIONS
n Charges Any Size Capacitor n Easily Adjustable Output Voltage n Drives High Current NMOS FETs n Primary-Side Sense—No Output Voltage Divider Necessary n Wide Input Range: 3V to 24V n Drives Gate to VCC – 2V n Available in 10-Lead MS Package n Emergency Warning Beacons n Professional Photoflash Systems n Security/Inventory Control Systems n High Voltage Power Supply n Electric Fences n Detonators All registered trademarks and trademarks are the property of their respective owners. *Protected by U.S. patents, including 6518733, 6636021. 300V, 6A Capacitor Charger VCC DONE CHARGE RVOUT RDCM GATE SOURCE VTRANS 60.4k 1:10 VOUT 300V VTRANS VCC 12V 100µF 43k 12m/uni03A9 3750a TA01a L T3750A GND RBG 100k 2.49k 100pF OFF ON 10µF 10µF 56µF ×2 + TIME (SECONDS) VOUT (V) 100 150 200 250 300 0.1 0.2 0.3 0.4 3750a TA03c 0.5 VTRANS = 18V VTRANS = 6V VTRANS = 12V 6A Charge Time
Rev. 0 For more information www.analog.com PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS Operating Temperature Range (Note 2)....–40°C to 85°C (Note 1) VTRANS DONE CHARGE VCC GND RBG RVOUT RDCM GATE SOURCE TOP VIEW MS PACKAGE 10-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 160°C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3750AEMS#PBF LT3750AEMS#TRPBF L THNS 10-Lead Plastic MSOP –40°C to 85°C Contact the factory for parts specified with wider operating temperature ranges. Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum VCC l 2.8 3 V Minimum VTRANS l 2.5 3 V VCC Quiescent Current Not Switching, CHARGE = 5V Not Switching, CHARGE = 0V 1.6 2.5 mA µA VTRANS Quiescent Current Not Switching, CHARGE = 5V Not Switching, CHARGE = 0V 140 250 µA µA CHARGE Pin Current CHARGE = 24V CHARGE = 5V CHARGE = 0V µA µA µA CHARGE Pin Enable Voltage l 0.87 1.1 V CHARGE Pin Disable Voltage DC Threshold Dynamic Threshold (Note 3) l l 0.2 0.6 V mV Minimum CHARGE Pin Low Time High→Low→High 20 µs VOUT Comparator T rip Voltage Measured RBG Pin l 1.215 1.24 1.265 V VOUT Comparator Overdrive 1µs Pulse Width, Measured on RBG Pin 30 mV RBG Pin Bias Current RBG = 1.2V 70 500 nA DCM Comparator T rip Voltage Measured as VDRAIN – VTRANS, RDCM = 43k (Note 4) l 5 36 80 mV Current Limit Comparator T rip Voltage l 68 78 88 mV DONE Output Signal High 100kΩ to 5V 4.9 5 V DONE Output Signal Low 100kΩ to 5V 0.1 0.2 V DONE Pin Leakage Current DONE = 2.5V 0.2 µA NMOS Minimum On Time 0.6 µs The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = VTRANS = 5V unless otherwise specified.
Rev. 0For more information www.analog.com TYPICAL PERFORMANCE CHARACTERISTICS Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT3750AE 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: Guaranteed by design, not tested in production. Note 4: Refer to Block Diagram for VDRAIN definition. PARAMETER CONDITIONS MIN TYP MAX UNITS GATE Rise Time 50 ns GATE High Voltage CGATE = 1nF, VCC = 5V CGATE = 1nF, VCC = 24V 3.8 22.6 4.5 23.5 V V GATE Turn Off Propagation Delay CGATE = 1nF 100 ns The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = VTRANS = 5V unless otherwise specified. VCC Pin Current VTRANS Pin Current CHARGE Pin Current CHARGE Pin Enable/Disable Voltage DONE Output Signal Low GATE High Voltage TEMPERATURE (°C) –50 –25 1.3 VCC PIN CURRENT (mA) 1.5 1.8 0 50 75 3750a G01 1.4 1.7 1.6 25 100 125 VCC = 24V VCC = 12V VCC = 3V TEMPERATURE (°C) –50 –25
100 VTRANS PIN CURRENT (µA)150
VTRANS = 24V VTRANS = 12V VTRANS = 3V VCHARGE (V) CHARGE PIN CURRENT (µA) 3750a G03 84 2012 24 40 –50°C 25°C 125°C TEMPERATURE (°C) –50 0.6 0.7 25 75 3750a G04 0.5 0.4 –25 0 50 100 125 0.3 0.2 0.1 0.8 CHARGE PIN VOLTAGE (V) CHARGE PIN DC ENABLE CHARGE PIN DC DISABLE LT3750A DYNAMIC DISABLE VOLTAGE TEMPERATURE (°C) –50 DONE PIN VOLTAGE (mV)100 120 140 160 –25 0 25 50 3750a G05 75 100 125 VDONE = 5V RDONE = 100k TEMPERATURE (°C) –50 –25 GATE PIN VOLTAGE (V) 0 50 75 3750a G06 25 100 125 VCC = 24V VCC = 12V VCC = 5V
Rev. 0 For more information www.analog.com TYPICAL PERFORMANCE CHARACTERISTICS DCM Comparator T rip Voltage VOUT Comparator T rip Voltage Current Limit Comparator T rip Voltage TEMPERATURE (°C) –50 –25 DCM COMPARATOR TRIP VOLTAGE (mV) 0 50 75 3750a G07 25 100 125 RDCM = 43k TEMPERATURE (°C) –50 –25 1.220VOUT COMPARATOR TRIP VOLTAGE (V) 1.228 1.240 0 50 75 3750a G08 1.224 1.236 1.232 25 100 125 TEMPERATURE (°C) –50 –25 CURRENT LIMIT COMPARATOR TRIP VOLTAGE (mV) 0 50 75 3750a G09 25 100 125 PIN FUNCTIONS VTRANS (Pin 1): T ransformer Supply Pin. Powers the pri- mary coil of the transformer as well as internal circuitry that performs boundary mode detection. Bypass at the pin with a 1µF to 10µF capacitor . Bypass the primary winding of the transformer with a large capacitor . DONE (Pin 2): Open Collector Indication Pin. When target output voltage is reached, an NPN transistor turns on. Requires a pull -up resistor or current source. Any fault conditions such as thermal shutdown or undervoltage lockout will also turn on the NPN. CHARGE (Pin 3): Charge Pin. Initiates a new charge cycle when brought high or discontinues charging and puts part into shutdown when low. To properly enable the device, a step input with a minimum ramp rate of 1V/µs is required. Drive to 1.1V or higher to enable the device; drive below 0.2V to disable the device. The LT3750A has additional circuitry to guarantee the GATE pin drives low within 200ns of the CHARGE pin being driven below 50mV, the dynamic threshold. VCC (Pin 4) : Input Supply Pin. Bypass locally with a ceramic capacitor . A 1µF to 10µF ceramic capacitor should be sufficient for most applications. GND (Pin 5): Ground Pin. Connect directly to local ground plane. SOURCE (Pin 6): Source Pin. Senses NMOS drain current. Connect NMOS source terminal and current sense resistor to this pin. The current limit is 78mV/RSENSE. GATE (Pin 7): Gate Pin. Connect NMOS gate terminal to this pin. Internal gate driver will drive voltage to within VCC – 2V during each switching cycle. RDCM (Pin 8): Discontinuous Mode Sense Pin. Senses when current in transformer has decayed to zero and ini- tiates a new charge cycle if output voltage target has not been reached. Place a resistor between this pin and the drain of the NMOS. A good choice is a 43k, 5% resistor . RVOUT (Pin 9): Output Voltage VI Converter Pin. Develops a current proportional to output capacitor voltage. Connect a resistor between this pin and the drain of the NMOS. RBG (Pin 10): Output Voltage Sense Pin. Senses the volt- age across the RBG resistor , which is proportional to the current flowing into the RVOUT pin. When voltage equals 1.24V, charging is disabled and DONE pin goes low. Connect a resistor ( 2.5k or less is recommended) from this pin to GND. A 2.49k, 1% resistor is a good choice.
Rev. 0For more information www.analog.com DIE TEMP 160°C + – 2.8V DONE VTRANS VTRANS VDRAIN CHARGE RDONE RBG VCC 2.5V VTRANS VCC UVLO VTRANS UVLO VOUT COMPARATOR DCM COMPARATOR CURRENT LIMIT COMPARATOR 36mV VTRANS TSD Q ENABLE R Q S 1.24V ONE SHOT RBGGND ONE SHOT Q R R 78mV RSENSE 3750a BD S RDCM 7GATE VCC SOURCE RDCM RVOUT COUTVOUT D1T1 1:N RVOUT BLOCK DIAGRAM
Rev. 0For more information www.analog.com OPERATION linearly at a rate (VTRANS – VDS(ON))/LPRI. The input volt- age is mirrored on the secondary winding –N • (VTRANS – VDS(ON)) which reverse biases the diode and prevents current flow in the secondary winding. Thus, energy is stored in the core of the transformer. 3. Secondary Energy Transfer When current limit is reached, the current limit compar - ator resets the NMOS on-latch and the device enters the third phase of operation, secondary energy transfer . The energy stored in the transformer core forward biases the diode and current flows into the output capacitor . During this time, the output voltage (neglecting the diode drop) is reflected back to the primary coil. If the target output voltage is reached, the VOUT comparator resets the master latch and the DONE pin goes low. Otherwise, the device enters the next phase of operation. 4. Discontinuous Mode Detection Once all the current is transferred to the output capacitor , (VOUT + VDIODE)/N will appear across the primary winding. A transformer with no energy cannot support a DC volt - age, so, the voltage across the primary will decay to zero. In other words, the drain of the NMOS will ring down from VTRANS + (VOUT + VDIODE)/N to VTRANS. When the drain voltage falls to VTRANS + 36mV, the DCM comparator sets the NMOS on-latch and a new charge cycle begins. Steps 2-4 continue until the target output voltage is reached.
sures when designing the LT3750A into applications. printed circuit board voltage breakdown requirements. ondary side of the transformer , and the output. otherwise, the LT3750A may overcharge the output. particular transformer characteristics. application with a 3A peak current. Figure 3. Typical Switching Period vs VOUT Table 1. Recommended T ransformers
2 VOUT(PK)+N•VTRANS( )
with adequate reverse recovery time. Table 2. Recommended Output Diodes winding current looks distorted instead of triangular . the amount of capacitive bypassing for the transformer . currents common in flyback regulators. Table 3. Recommended Output Capacitor Vendors
Table 4 lists recommended NMOS transistors. increases the peak current limit by (VTRANS)(tDELAY)/LPRI. Table 4. Recommended NMOS T ransistors Use at least 1% tolerance resistors for R VOUT and R BG. 2.5k for typical applications. it reaches a plateau at maximum VOUT. mode comparator threshold which is nominally 36mV. the diode forward voltage drop divided by N.
- Minimize the area of the high voltage end of the sec -
- Provide sufficient spacing for all high voltage nodes
- Keep the electrical path formed by C1, the primary of T1
- Reduce difference between CHARGE pin control cir -
ground to LT3750A ground, Pin 5.
- +
Figure 4. Recommended Board Layout
Rev. 0 For more information www.analog.com APPLICATIONS INFORMATION 300V, 3A Capacitor Charger 3A Charging Efficiency 3A Charging Time Typical Switching Waveforms VCC DONE CHARGE RVOUT RDCM GATE SOURCE VTRANS 60.4k 1:10 VOUT 300V VTRANS VCC 12V 100µF 43k 25m/uni03A9 3750a TA02a L T3750A GND RBG 100k 4, 5 6, 7 2.49k 33pF OFF ON 10µF 10µF 56µF + C1: 25V X5R OR X7R CERAMIC CAPACITOR C2: 25V X5R OR X7R CERAMIC CAPACITOR C3: 25V SANYO OS-CON 25SVP56M C4: 330V RUBYCON PHOTOFLASH CAPACITOR D1: DIODES INC. MURS160 M1: NXP PHT6NQ10T T1: TDK DCT15EFD-U44S003 FL YBACK TRANSFORMER VOUT (V) EFFICIENCY (%) 100 50 100 150 200 3750a TA02b 250 300 VTRANS = 18V VTRANS = 6VVTRANS = 12V TIME (SECONDS) VOUT (V) 100 150 200 250 300 0.2 0.4 0.6 0.8 3750a TA02c 1.0 VTRANS = 18V VTRANS = 6V VTRANS = 12V NMOS DRAIN CURRENT 1A/DIV NMOS DRAIN VOL TAGE 20V/DIV 5µs/DIV 3750a TA02d
Rev. 0For more information www.analog.com TYPICAL APPLICATIONS 300V, 6A Capacitor Charger 6A Charging Efficiency 6A Charging Time Typical Switching Waveforms VCC DONE CHARGE RVOUT RDCM GATE SOURCE VTRANS 60.4k 1:10 VOUT 300V VTRANS VCC 12V 100µF 43k 12m/uni03A9 3750a TA03a L T3750A GND RBG 100k 2.49k 100pF OFF ON 10µF 10µF 56µF ×2 + C1: 25V X5R OR X7R CERAMIC CAPACITOR C2: 25V X5R OR X7R CERAMIC CAPACITOR C3: 25V SANYO OS-CON 25SVP56M C4: 330V RUBYCON PHOTOFLASH CAPACITOR D1: DIODES INC. MURS160 M1: NXP PHT6NQ10T T1: TDK DCT20EFD-U32S003 FL YBACK TRANSFORMER 3, 4, 5, 6 7, 8, 9, 10 VOUT (V) EFFICIENCY (%) 100 50 100 150 200 3750a TA03b 250 300 VTRANS = 18V VTRANS = 6V VTRANS = 12V TIME (SECONDS) VOUT (V) 100 150 200 250 300 0.1 0.2 0.3 0.4 3750a TA03c 0.5 VTRANS = 18V VTRANS = 6V VTRANS = 12V NMOS DRAIN CURRENT 2A/DIV NMOS DRAIN VOL TAGE 20V/DIV 5µs/DIV 3750a TA03d
Rev. 0 For more information www.analog.com VCC DONE CHARGE RVOUT RDCM GATE SOURCE VTRANS 60.4k 1:10 VOUT 300V VTRANS VCC 12V 100µF 43k 8m/uni03A9 3750a TA04a L T3750A GND RBG 100k 2.49k 100pF OFF ON 10µF C1: 25V X5R OR X7R CERAMIC CAPACITOR C2: 25V X5R OR X7R CERAMIC CAPACITOR C3: 25V SANYO OS-CON 25SVP56M C4: 330V RUBYCON PHOTOFLASH CAPACITOR D1: DIODES INC. MURS160 M1: NXP PHM2INQ15T T1: TDK DCT20EFD-U32S003 FL YBACK TRANSFORMER 10µF 56µF ×3 + 3, 4, 5, 6 7, 8, 9, 10 300V, 9A Capacitor Charger 9A Charging Efficiency 9A Charging Time Typical Switching Waveforms VOUT (V) EFFICIENCY (%) 100 50 100 150 200 3750a TA04b 250 300 VTRANS = 18V VTRANS = 6V VTRANS = 12V TIME (SECONDS) VOUT (V) 100 150 200 250 300 0.05 0.10 0.15 0.20 3750a TA04c 0.300.25 VTRANS = 18V VTRANS = 6V VTRANS = 12V NMOS DRAIN CURRENT 4A/DIV NMOS DRAIN VOL TAGE 20V/DIV 5µs/DIV 3750a TA04d
Rev. 0For more information www.analog.com Information furnished by Analog Devices is believed to be accurate and reliable. However , no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. PACKAGE DESCRIPTION MSOP (MS) 0213 REV F 0.53 ±0.152 (.021 ±.006) SEATING PLANE 0.18 (.007) 1.10 (.043) MAX 0.17 –/uni00A00.27 (.007 – .011) TYP 0.86 (.034) REF 0.50 (.0197) BSC 1 2 3 4 5 4.90 ±0.152 (.193 ±.006) 0.497 ±0.076 (.0196 ±.003) REF8910 7 6 3.00 ±0.102 (.118 ±.004) (NOTE 3) 3.00 ±0.102 (.118 ±.004) (NOTE 4) NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 0.254 (.010) 0° – 6° TYP DETAIL “A” DETAIL “A” GAUGE PLANE 5.10 (.201) MIN 3.20 – 3.45 (.126 – .136) 0.889 ±0.127 (.035 ±.005) RECOMMENDED SOLDER PAD LAYOUT 0.305 ±0.038 (.0120 ±.0015) TYP 0.50 (.0197) BSC 0.1016 ±0.0508 (.004 ±.002) 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661 Rev F)
Rev. 0 For more information www.analog.com ANALOG DEVICES, INC. 2021 www.analog.com RELATED PARTS TYPICAL APPLICATION PART NUMBER DESCRIPTION COMMENTS LT3420/LT3420-1 1.4A/1A, Photoflash Capacitor Charger with Automatic Top-Off Charges 220µF to 320V in 3.7 Seconds from 5V, VIN: 2.2V to 16V, ISD < 1µA, 10-Lead MS Package LT3468/LT3468-1 LT3468-2 1.4A, 1A, 0.7A, Photoflash Capacitor Charger VIN: 2.5V to 16V, Charge Time: 4.6 Seconds for LT3468 (0V to 320V, 100µF, VIN = 3.6V), ISD < 1µA, ThinSOT Package LT3484-0/LT3484-1 LT3484-2 1.4A, 0.7A, 1A Photoflash Capacitor Charger VIN: 1.8V to 16V, Charge Time: 4.6 Seconds for LT3484-0 (0V to 320V, 100µF, VIN = 3.6V), ISD < 1µA, 2mm × 3mm 6-Lead LT3485-0/LT3485-1 LT3485-2/LT3485-3 1.4A, 0.7A, 1A, 2A Photoflash Capacitor Charger with Output Voltage Monitor and Integrated IGBT VIN: 1.8V to 10V, Charge Time: 3.7 Seconds for LT3485-0 (0V to 320V, 100µF, VIN = 3.6V), ISD < 1µA, 3mm × 3mm 10-Lead DFN Driver LT3751 High Voltage Flyback Capacitor Charger Controller VIN Range Depends on the Choice of External Components, 4mm × 5mm 20-Lead QFN and 20-Lead TSOP Packages VCC DONE CHARGE RVOUT RDCM GATE SOURCE VTRANS 60.4k 1:10 VOUT 300V VTRANS VCC 12V 2.5mF 43k 8mΩ 3750a TA05a L T3750A GND RBG 100k 2.49k 100pF OFF ON 10µF C1, C2: 25V X5R OR X7R CERAMIC CAPACITOR C3: 25V SANYO OS-CON 25SVP56M C4: CORNELL DUBILIER 7P252V360N082 D1: DIODES INC. MURS160 M1: NXP PHM21NQ15T T1: WURTH 750032052 FL YBACK TRANSFORMER 10µF 56µF ×3 + 4, 5 6, 7 300V, 9A 2.5mF Capacitor Charger Efficiency Charge Time VOUT (V) EFFICIENCY (%)80 100 50 100 150 200 3750a TA05b 250 300 VTRANS = 18V VTRANS = 6V VTRANS = 12V TIME (SECONDS) VOUT (V) 100 150 200 250 300 1 2 3 4 5 6 3750a TA05c VTRANS = 18V VTRANS = 6V VTRANS = 12V