LT3573 LINER
Document overview
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Technical content
FEATURES
APPLICATIONS
DESCRIPTION
Isolated Flyback Converter Without an Opto-Coupler The L T®3573 is a monolithic switching regulator specifi - cally designed for the isolated fl yback topology. No third winding or optoisolator is required for regulation. The part senses the isolated output voltage directly from the primary side fl yback waveform. A 1.25A, 60V NPN power switch is integrated along with all control logic into a 16- lead MSOP package. The L T3573 operates with input supply voltages from 3V to 40V , and can deliver output power up to 7W with no external power devices.The L T3573 utilizes boundary mode operation to provide a small magnetic solution with improved load regulation. 5V Isolated Flyback Converter n 3V to 40V Input Voltage Range n 1.25A, 60V Integrated NPN Power Switch n Boundary Mode Operation n No T ransformer Third Winding or Optoisolator Required for Regulation n Improved Primary-Side Winding Feedback Load Regulation n V OUT Set with T wo External Resistors n BIAS Pin for Internal Bias Supply and Power NPN Driver n Programmable Soft-Start n Programmable Power Switch Current Limit n Thermally Enhanced 16-Lead MSOP n Industrial, Automotive, Medical n Low Power PoE L T, L TC and L TM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Patents pending. Load Regulation SHDN/UVLO TC RILIM SS RFB RREF SW VC GND TEST BIAS L T3573
3573 TA01
28.7k 10k 20k VIN 12V TO 24V VOUT+ 5V , 0.7A VOUT– VIN 3:1 357k 51.1k 10μF 2.6μH24μH 47μF 10nF 1nF 4.7μF 6.04k 80.6k B340A 1N4148 0.22μF IOUT (mA) OUTPUT VOL TAGE ERROR (%) 400 800200 600 1000 1200 1400
3573 TA01b
VIN = 12V VIN = 24V TYPICAL APPLICATION
Operating Junction Temperature Range (Note 2) ORDER INFORMATION ELECTRICAL CHARACTERISTICS The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN = 12V , unless otherwise noted. LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE L T3573EMSE#PBF L T3573EMSE#TRPBF 3573 16-Lead Plastic MSOP –40°C to 125°C L T3573IMSE#PBF L T3573IMSE#TRPBF 3573 16-Lead Plastic MSOP –40°C to 125°C Consult L TC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container . For more information on lead free part marking, go to: http://www.linear .com/leadfree/ For more information on tape and reel specifi cations, go to: http://www.linear .com/tapeandreel/ PARAMETER CONDITIONS MIN TYP MAX UNITS Input Voltage Range l 34 0 V Quiescent Current SS = 0V VSHDN/UVLO = 0V 3.5 mA μA Soft-Start Current SS = 0.4V 7 μA SHDN/UVLO Pin Threshold UVLO Pin Voltage Rising l 1.15 1.22 1.29 V SHDN/UVLO Pin Hysteresis Current V UVLO = 1V 2 2.5 3 μA Soft-Start Threshold 0.7 V Maximum Switching Frequency 1000 kHz Switch Current Limit R ILIM = 10k 1.25 1.55 1.85 A Minimum Current Limit V C = 0V 140 200 260 mA Switch VCESAT ISW = 0.5A 150 250 mV RREF Voltage V IN = 3V l 1.21 1.20 1.23 1.25 1.25 V RREF Voltage Line Regulation 3V < V IN < 40V 0.01 0.03 %/ V RREF Pin Bias Current (Note 3) l 100 600 nA IREF Reference Current Measured at R FB Pin with RREF = 6.49k 190 μA PIN CONFIGURATION TOP VIEW MSE PACKAGE 16-LEAD PLASTIC MSOP GND TEST GND SW VIN BIAS SHDN/UVLO GND GND TC R REF RFB VC RILIM SS GND TJMAX = 125°C, θJA = 50°C/W , θJC = 10°C/W EXPOSED PAD (PIN 17) IS GND, MUST BE CONNECTED TO GND
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 L T3573E is guaranteed to meet performance specifi cations from 0°C to 125°C junction temperature. Specifi cations over the –40°C to 125°C operating junction temperature range are assured by design characterization and correlation with statistical process controls. The L T3573I is guaranteed over the full –40°C to 125°C operating junction temperature range. Note 3: Current fl ows out of the R REF pin. PARAMETER CONDITIONS MIN TYP MAX UNITS Error Amplifi er Voltage Gain V IN = 3V 150 V/V Error Amplifi er T ransconductance ΔI = 10μA, VIN = 3V 150 μmhos Minimum Switching Frequency V C = 0.35V 40 kHz TC Current into RREF RTC = 20.1k 27.5 μA BIAS Pin Voltage I BIAS = 30mA 2.9 3 3.1 V ELECTRICAL CHARACTERISTICS The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN = 12V , unless otherwise noted. TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage Quiescent Current Bias Pin Voltage TA = 25°C, unless otherwise noted. TEMPERATURE (°C) –50
4.80 VOUT (V)
4.85 4.95 5.00 5.05 5.20 5.15 0 50 75 4.90 5.10 –25 25 100 125
3573 G01
TEMPERATURE (°C) –50 IQ (mA) 0 50 75 –25 25 100 125
3573 G02
VIN = 40V VIN = 5V TEMPERATURE (°C) –50 2.0 BIAS VOLTAGE (V)2.4 2.6 2.8 3.2 0 50 75 2.2 3.0 –25 25 100 125
3573 G03
VIN = 40V VIN = 12V
TYPICAL PERFORMANCE CHARACTERISTICS Switch VCESAT Switch Current Limit Switch Current Limit vs R ILIM SHDN/UVLO Falling Threshold SS Pin Current TA = 25°C, unless otherwise noted. SWITCH CURRENT (A) SWITCH VCESAT VOLTAGE (mV) 100 200 300 400 150 250 350 1.50
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125°C 25°C –50°C TEMPERATURE (°C) –50 CURRENT LIMIT (A) 1.2 1.4 1.6 1.0 0.8 –25 25 0 50 75 100 125 0.2 0.6 1.8 0.4
3573 G05
RILIM = 10k TEMPERATURE (°C) –60 SHDN/UVLO VOL TAGE (V) 1.24 1.26 1.22 –20 20–40 120 04 0 10060 140 1.20 1.18 1.28
3573 G07
RILIM RESISTANCE (k) CURRENT LIMIT (A) 1.2 1.4 1.6 1.0 0.8 10 30 20 40 50 0.2 0.6 1.8 0.4
3573 G06
TEMPERATURE (°C) –60 SS PIN CURRENT (μA) –20 20–40 120 04 0 10060 140
3573 G08
GND: Ground. TEST : This pin is used for testing purposes only and must be connected to ground for the part to operate properly. SW: Collector Node of the Output Switch. This pin has large currents fl owing through it. Keep the traces to the switching components as short as possible to minimize electromagnetic radiation and voltage spikes. V IN: Input Voltage. This pin supplies current to the internal start-up circuitry and as a reference voltage for the DCM comparator and feedback circuitry. This pin must be locally bypassed with a capacitor . BIAS: Bias Voltage. This pin supplies current to the switch driver and internal circuitry of the L T3573. This pin must be locally bypassed with a capacitor . This pin may also be connected to V IN if a third winding is not used and if VIN ≤ 15V . If a third winding is used, the BIAS voltage should be lower than the input voltage for proper operation. SHDN/UVLO: Shutdown/Undervoltage Lockout. A resistor divider connected to V IN is tied to this pin to program the minimum input voltage at which the L T3573 will operate. At a voltage below ~0.7V , the part draws no quiescent current. When below 1.25V and above ~0.7V , the part will draw 10μA of current, but internal circuitry will remain off. Above 1.25V , the internal circuitry will start and a 10μA current will be fed into the SS pin. When this pin falls below 1.25V , 2.5μA will be pulled from the pin to provide programmable hysteresis for UVLO. R ILIM: Maximum Current Limit Adjust Pin. A resistor should be tied to this pin to ground to set the current limit. Use a 10k resistor for the full current capabilities of the switch. SS: Soft-Start Pin. Place a soft-start capacitor here to limit start-up inrush current and output voltage ramp rate. Switching starts when the voltage at this pin reaches ~0.7V . V C: Compensation Pin for Internal Error Amplifi er . Connect a series RC from this pin to ground to compensate the switching regulator . A 100pF capacitor in parallel helps eliminate noise. R FB: Input Pin for External Feedback Resistor . This pin is connected to the transformer primary (V SW). The ratio of this resistor to the R REF resistor , times the internal bandgap reference, determines the output voltage (plus the effect of any non-unity transformer turns ratio). The average current through this resistor during the fl yback period should be approximately 200μA. For nonisolated applications, this pin should be connected to V IN. RREF: Input Pin for External Ground-Referred Reference Resistor . This resistor should be in the range of 6k, but for convenience, need not be precisely this value. For nonisolated applications, a traditional resistor voltage divider may be connected to this pin. T C: Output Voltage Temperature Compensation. Connect a resistor to ground to produce a current proportional to absolute temperature to be sourced into the R REF node. ITC = 0.55V/RTC. Exposed Pad: Ground. The Exposed Pad of the package provides both electrical contact to ground and good thermal contact to the printed circuit board. The Exposed Pad must be soldered to the circuit board for proper operation and should be well connected with many vias to an internal ground plane.
VOUT– VIN TC BIAS SS SWVIN VIN GND 120mV1.22V VC N:1 7μA 20μA RSENSE 0.02Ω L1A L1B INTERNAL REFERENCE AND REGULATORS OSCILLATOR TC CURRENT ONE SHOT R Q S S gm 2.5μA 3573 BD 1.22V DRIVER SHDN/UVLO RILIM RFB RREF
The L T3573 is a current mode switching regulator IC designed specifi cally for the isolated fl yback topology. The special problem normally encountered in such cir- cuits is that information relating to the output voltage on the isolated secondary side of the transformer must be communicated to the primary side in order to maintain regulation. Historically, this has been done with optoisola- tors or extra transformer windings. Optoisolator circuits waste output power and the extra components increase the cost and physical size of the power supply. Optoiso- lators can also exhibit trouble due to limited dynamic response, nonlinearity, unit-to-unit variation and aging over life. Circuits employing extra transformer windings also exhibit defi ciencies. Using an extra winding adds to the transformer’s physical size and cost, and dynamic response is often mediocre. The L T3573 derives its information about the isolated output voltage by examining the primary side fl yback pulse waveform. In this manner , no optoisolator nor extra transformer winding is required for regulation. The output voltage is easily programmed with two resistors. Since this IC operates in boundary control mode, the output voltage is calculated from the switch pin when the secondary cur- rent is almost zero. This method improves load regulation without external resistors and capacitors. The Block Diagram shows an overall view of the system. Many of the blocks are similar to those found in traditional switching regulators including: internal bias regulator , oscillator , logic, current amplifi er and comparator , driver , and output switch. The novel sections include a special fl yback error amplifi er and a temperature compensation circuit. In addition, the logic system contains additional logic for boundary mode operation, and the sampling error amplifi er . The L T3573 features a boundary mode control method, where the part operates at the boundary between continu- ous conduction mode and discontinuous conduction mode. The V C pin controls the current level just as it does in normal current mode operation, but instead of turning the switch on at the start of the oscillator period, the part detects when the secondary side winding current is zero. Boundary Mode Operation Boundary mode is a variable frequency, current-mode switching scheme. The switch turns on and the inductor current increases until a V C pin controlled current limit. The voltage on the SW pin rises to the output voltage divided by the secondary-to-primary transformer turns ratio plus the input voltage. When the secondary current through the diode falls to zero, the SW pin voltage falls below V IN. A discontinuous conduction mode (DCM) comparator detects this event and turns the switch back on. Boundary mode returns the secondary current to zero every cycle, so the parasitic resistive voltage drops do not cause load regulation errors. Boundary mode also allows the use of a smaller transformer compared to continuous conduction mode and no subharmonic oscillation. At low output currents the L T3573 delays turning on the switch, and thus operates in discontinuous mode. Unlike a traditional fl yback converter , the switch has to turn on to update the output voltage information. Below 0.6V on the V C pin, the current comparator level decreases to its minimum value, and the internal oscillator frequency decreases in frequency. With the decrease of the internal oscillator , the part starts to operate in DCM. The output current is able to decrease while still allowing a minimum switch off-time for the error amp sampling circuitry. The typical minimum internal oscillator frequency with V C equal to 0V is 40kHz.
ERROR AMPLIFIER—PSEUDO DC THEORY In the Block Diagram, the RREF (R4) and RFB (R3) resistors can be found. They are external resistors used to program the output voltage. The L T3573 operates much the same way as traditional current mode switchers, the major difference being a different type of error amplifi er which derives its feedback information from the fl yback pulse. Operation is as follows: when the output switch, Q1, turns off, its collector voltage rises above the V IN rail. The am- plitude of this fl yback pulse, i.e., the difference between it and VIN, is given as: V FLBK = (VOUT + VF + ISEC • ESR) • NPS VF = D1 forward voltage ISEC = T ransformer secondary current ESR = Total impedance of secondary circuit N PS = T ransformer effective primary-to-secondary turns ratio The fl yback voltage is then converted to a current by the action of RFB and Q2. Nearly all of this current fl ows through resistor R REF to form a ground-referred volt- age. This voltage is fed into the fl yback error amplifi er . The fl yback error amplifi er samples this output voltage information when the secondary side winding current is zero. The error amplifi er uses a bandgap voltage, 1.23V , as the reference voltage. The relatively high gain in the overall loop will then cause the voltage at the R REF resistor to be nearly equal to the bandgap reference voltage VBG. The relationship between VFLBK and VBG may then be expressed as: α V R V R or VV R R FLBK FB BG REF FLBK BG FB REF ⎠⎟ = = ⎛ ⎝⎝⎜ α α = Ratio of Q1 IC to IE, typically ≈ 0.986 VBG = Internal bandgap reference In combination with the previous VFLBK expression yields an expression for VOUT, in terms of the internal reference, programming resistors, transformer turns ratio and diode forward voltage drop: VV R RN VI E SOUT BG FB REF PS FS E C= ⎛ ⎠⎟ −−1 α (R R) Additionally, it includes the effect of nonzero secondary output impedance (ESR). This term can be assumed to be zero in boundary control mode. More details will be discussed in the next section. Temperature Compensation The fi rst term in the V OUT equation does not have a tem- perature dependence, but the diode forward drop has a signifi cant negative temperature coeffi cient. To compen- sate for this, a positive temperature coeffi cient current source is connected to the R REF pin. The current is set by a resistor to ground connected to the TC pin. To cancel the temperature coeffi cient, the following equation is used: δ δ δ δ δ V T R RN V T or R R NV FF B TC PS TC TC FB PS = − , FF TC FB PST V T R N/ δ δ δ ≈ (δVF/δT) = Diode’s forward voltage temperature coef- fi cient (δVTC/δT) = 2mV VTC = 0.55V The resistor value given by this equation should also be verifi ed experimentally, and adjusted if necessary to achieve optimal regulation over temperature. The revised output voltage is as follows: VV R RN V V R OUT BG FB REF PS F TC TC = ⎛ ⎠⎟ − − ⎛ α ⎝⎝⎜ ⎠⎟ – ( )R N IE S RFB PS SECα APPLICATIONS INFORMATION
required for proper L T3573 operation. SW pin when the secondary winding conducts current. the power switch current is highest. not signifi cantly affect output regulation. Table 1. Common Resistor Values for 1:1 T ransformers
Table 2. Common Resistor Values for 2:1 T ransformers Table 3. Common Resistor Values for 3:1 T ransformers Table 4. Common Resistor Values for 4:1 T ransformers power possible for the output voltages 3.3V , 5V , and 12V . of output power at given input voltages. but lowers to fi ve watts at 20V . Figure 1. Output Power for 3.3V Output Figure 2. Output Power for 5V Output Figure 3. Output Power for 12V Output
3573 F01
3573 F02
3573 F03
TRANSFORMER DESIGN CONSIDERATIONS T ransformer specifi cation and design is perhaps the most critical part of successfully applying the L T3573. In addition to the usual list of caveats dealing with high frequency isolated power supply transformer design, the following information should be carefully considered. Linear Technology has worked with several leading mag- netic component manufacturers to produce pre-designed fl yback transformers for use with the L T3573. Table 5 shows the details of several of these transformers. Table 5. Predesigned T ransformers—Typical Specifi cations, Unless Otherwise Noted PA2363NL 15.24 × 13.1 × 11.45 25 850 5:1:1 117 7.5 Pulse Engineering 12V- >5V , 1A PA2454NL 15.24 × 13.1 × 11.45 24 430 3:1:1 82 11 Pulse Engineering 24V- >5V , 1A PA2455NL 15.24 × 13.1 × 11.45 25 450 2:1:1 82 22 Pulse Engineering 24V- >12V , 0.5A PA2456NL 15.24 × 13.1 × 11.45 25 390 1:1:1 82 84 Pulse Engineering 12V- >12V , 0.3A 24V- >12V , 0.4A 36V- >5V , 0.6A PA2626NL 12.70 × 10.67 × 9.14 30 403 3:1:1 240 66 Pulse Engineering 24V- >5V , 1A PA2627NL 15.24 × 13.1 × 11.45 50 766 3:1:1 420 44 Pulse Engineering 24V- >5V , 1A GA3430-BL 15.24 × 12.7 × 11.43 25 685 5:1:1 90 5.5 Coilcraft 12V- >5V , 1A 750310471 15.24 × 13.3 × 11.43 25 350 3:1:1 57 11 Würth Elektronik 24V- >5V , 1A 750310562 15.24 × 13.3 × 11.43 25 330 2:1:1 60 20 Würth Elektronik 24V- >12V , 0.5A 24V- >12V , 0.4A 36V- >5V , 0.6A 750310564 15.24 × 13.3 × 11.43 63 450 3:1:1 115 50 Würth Elektronik 24V- >±5V , 0.5A 750370040 9.14 × 9.78 × 10.54 30 150 3:1:1 60 12.5 Würth Elektronik 24V- >5V , 1A 750370041 9.14 × 9.78 × 10.54 50 450 3:1:1 190 26 Würth Elektronik 24V- >5V , 1A 750370047 13.35 × 10.8 × 9.14 30 150 3:1:1 60 12.5 Würth Elektronik 24V- >5V , 1A L11-0059 9.52 × 9.52 × 4.95 24 3:1 266 266 BH Electronics 24V- >5V , 1A L10-1019 9.52 × 9.52 × 4.95 18 1:1 90 90 BH Electronics 5V- >5V , 0.2A
setting total turns and mutual inductance. an upper limit on the turns ratio, N, for a given application. long enough to accurately measure the output voltage. can be chosen for the absolute smallest transformer size. breakdown voltage of the internal power switch. details of several of these transformers. Figure 5. In most applications, there will be a very fast also determines the maximum turns ratio. spike. The leakage spike must always be kept below 60V .
Figure 5. Maximum Voltages for SW Pin Flyback WaveformFigure 4. RCD Clamp Figure 6. Good Snubber Diode Limits SW Pin Voltage Figure 7. Bad Snubber Diode Does Not Limit SW Pin Voltage
3573 F06
3573 F07
3573 F04
due to the boundary mode operation of the L T3573. threshold on the SHDN/UVLO pin for VIN rising is 1.22V . Figure 8. Undervoltage Lockout (UVLO)
3573 F08
The L T3573 is compensated using an external resistor- capacitor network on the VC pin. Typical values are in the range of RC = 50k and CC = 1nF (see the numerous sche- matics in the Typical Applications section for other possible values). If too large of an R C value is used, the part will be more susceptible to high frequency noise and jitter . If too small of an R C value is used, the transient performance will suffer. The value choice for C C is somewhat the inverse of the RC choice: if too small a CC value is used, the loop may be unstable, and if too large a C C value is used, the transient performance will also suffer. T ransient response plays an important role for any DC/DC converter . Design Example The following example illustrates the converter design process using L T3573. Given the input voltage of 20V to 28V , the required output is 5V , 1A. V IN(MIN) = 20V , VIN(MAX) = 28V, VOUT = 5V , VF = 0.5V and IOUT = 1A 1. Select the transformer turns ratio to accommodate the output. The output voltage is refl ected to the primary side by a factor of turns ratio N. The switch voltage stress V SW is expressed as: N N N VV N V V V P S SW MAX IN OUT F =+ +<() () 5 0 Or rearranged to: N V VV IN MAX OUT F 50 () On the other hand, the primary side current is multiplied by the same factor of N. The converter output capability is: ID N I D NV V VN OUT MAX PK OUT F IN () . ( ) = + 0 8 1 1 (()VVOUT F+ Minimum Load Requirement The L T3573 obtains output voltage information through the transformer while the secondary winding is conducting current. During this time, the output voltage (multiplied times the turns ratio) is presented to the primary side of the transformer . The L T3573 uses this refl ected signal to regulate the output voltage. This means that the L T3573 must turn on every so often to sample the output voltage, which delivers a small amount of energy to the output. This sampling places a minimum load requirement on the output of 1% to 2% of the maximum load. BIAS Pin Considerations For applications with an input voltage less than 15V , the BIAS pin is typically connected directly to the V IN pin. For input voltages greater than 15V , it is preferred to leave the BIAS pin separate form the V IN pin. In this condition, the BIAS pin is regulated with an internal LDO to a voltage of 3V . By keeping the BIAS pin separate from the input voltage at high input voltages, the physical size of the capacitors can be minimized (the BIAS pin can then use a 6.3V or 10V rated capacitor). Overdriving the BIAS Pin with a Third Winding The L T3573 provides excellent output voltage regulation without the need for an optocoupler , or third winding, but for some applications with higher input voltages (>20V), it may be desirable to add an additional winding (often called a third winding) to improve the system effi ciency. For proper operation of the L T3573, if a winding is used as a supply for the BIAS pin, ensure that the BIAS pin voltage is at least 3.15V and always less than the input voltage. For a typical 24V IN application, overdriving the BIAS pin will improve the effi ciency gain 4-5%.
Table 6. Switch Voltage Stress and Output Current Capability vs
- Select the transformer primary inductance for target
range in order to minimize the output ripple. Note: The switching frequency is calculated at maximum output. chosen as the fl yback transformer . Coiltronics Versa-Pac may be used.
- Select the output diodes and output capacitor .
calculates the output voltage ripple.
- Select the snubber circuit to clamp the switch
turn-off due to the leakage inductance of the transformer .
9 shows the RCD snubber in a fl yback converter . A typical switch node waveform is shown in Figure 10. eventually dissipated in the snubber resistor . to the output voltage sensing.
- Select the feedback resistor for proper output
voltage. RREF is selected as 6.04k.
- Optimize the compensation network to improve the
compensation resistor not greater than 50k.
- Current limit resistor , soft-start capacitor and UVLO
capacitor helps during the start-up of the fl yback converter . tion range. These equations are aforementioned. Figure 9. RCD Snubber in a Flyback Converter Figure 10. Typical Switch Node Waveform
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3573 F10
±12V Isolated Flyback Converter TYPICAL APPLICATIONS SHDN/UVLO TC SS SW VC GND BIAS L T3573
3573 TA02
28.7k 10k VIN VOUT+ 5V , 350mA VOUT– VIN 3:1 D1 VIN 200k 90.9k 10μF C5 47μF 24μH 2.6μH T1: PULSE PA2454NL OR WÜRTH ELEKTRONIK 750310471 D1: B340A D2: 1N4148 C5: MURATA, GRM32ER71A476K 6.04k 80.6k 10nF SW 1000pF 57.6k 0.22 μF TEST RILIM RFB RREF SHDN/UVLO TC SS SW VC GND BIAS L T3573
3573 TA03
2:1:1 VIN 200k 90.9k 10μF T1 43.6μH T1: COIL TRONICS VPH1-0076-R D1, D2: B240A D3: 1N4148 C5, C6: MURATA, GRM32ER71A476K 6.04k 118k VOUT1+ 12V , 100mA VOUT1– 47μF10.9μH VOUT2+ VOUT2– –12V , 100mA 47μF10.9μH 10nF SW 3300pF 56.2k 0.22 μF TEST RILIM RFB RREF Low Input Voltage 5V Isolated Flyback Converter
5V , 700mA VOUT– 47μF2.6μH T1: PULSE PA2454NL OR WÜRTH ELEKTRONIK 750370047 D1: B340A D3: 1N4148 C5: MURATA, GRM32ER71A476K SHDN/UVLO TC SS SW VC GND BIAS L T3573
3573 TA04
28.7k 10k VIN 12V TO 24V (*40V) VIN 3:1:1 499k 71.5k 10μF T1 24μH 6.04k 80.6k 1000pF 4.7μF 10nF 45.3k *OPTIONAL THIRD WINDING FOR 40V OPERATION L1C 2.6μH 0.22μF TEST RILIM RFB RREF 5V Isolated Flyback Converter Effi ciency IOUT (mA) EFFICIENCY (%) 400 800200 600 1000 1200 1400
3573 TA04b
VIN = 12V VIN = 24V
3573 TA05
19.1k 10k VIN 12V TO 24V (*40V) VIN 4:1:1 499k 71.5k 10μF T1 24μH T1: PULSE PA2362NL OR COILCRAFT GA3429-BL D1: B340A D3: 1N4148 6.04k 76.8k VOUT+ 3.3V , 1A VOUT– 47μF1.5μH 1500pF 4.7μF 10nF 25.5k *OPTIONAL THIRD WINDING FOR 40V OPERATION L1C 1.5μH 0.22 μF TEST RILIM RFB RREF 3.3V Isolated Flyback Converter TYPICAL APPLICATIONS 12V Isolated Flyback Converter SHDN/UVLO TC SS SW VC GND BIAS L T3573
3573 TA06
12V , 400mA VOUT– VIN 3:1 D1 VIN 499k 71.5k 10μF C5 47μF 58.5μH 6.5μH T1: COIL TRONICS VP1-0102-R D1: B340A D2: 1N4148 6.04k 178k 10nF 4700pF 40.2k 0.22 μF TEST RILIM RFB RREF
Four Output 12V Isolated Flyback Converter SHDN/UVLO TC SS SW VC GND BIAS L T3573
3573 TA07
2:1:1:1:1 VIN 499k 71.5k 10μF 43.6μH T1: COIL TRONICS VPH1-0076-R D1-D4: B240A D5: 1N4148 6.04k 118k VOUT1+ 12V , 60mA VOUT1– D1 C5 47μF10.9μH VOUT2+ 12V , 60mA VOUT2– D2 C6 47μF10.9μH VOUT3+ 12V , 60mA VOUT3– D3 C7 47μF10.9μH VOUT4+ 12V , 60mA VOUT4– D4 C8 47μF10.9μHC2 10nF 0.01μF 20k 0.22 μF TEST RILIM RFB RREF 5V Isolated Flyback Converter Using a Tiny Transformer SHDN/UVLO TC SS SW VC GND BIAS L T3573
3573 TA08
28.7k 30k VIN 12V VOUT 5V , 600mA VOUT– VIN 3:1 D1 VIN 200k 90.9k 10μF C5 47μF 20μH 2.2μH T1: BH ELECTRONICS L11-0059 D1: B340A D2: 1N4148 6.04k 80.6k 10nF 1000pF 47.5k 0.22 μF TEST RILIM RFB RREF
5V Isolated Flyback Converter Using Coupling Inductor SHDN/UVLO TC SS SW VC GND BIAS L T3573
3573 TA09
26.1k 10k VIN VOUT+ 5V , 0.2A VOUT– VIN 1:1 D1 VIN 200k 90.9k 10μF 47μF 23.6μH 23.6μH T1: BH ELECTRONICS, L10-1022 D1: B220A D2: CMD5H-3 6.04k 26.1k 10nF 1500pF 56.2k 0.22 μF TEST RILIM RFB RREF SHDN/UVLO TC SS SW VC GND BIAS L T3573
3573 TA10
20.5k 10k VIN 5V TO 15V VOUT+ 300V , 5mA VOUT– VIN 1:17 D1 VIN 100k 36k 10μF C5, 0.47μF , 400V POL Y FILM 26μH 7.583mH D1: TOSHIBA CRF02 D2: ZETEX ZHCS 506TA 6.04k 90.9k 10nF 1000pF 10k 4.7k 0.22 μF TEST RILIM RFB RREF 300V Isolated Flyback Converter TYPICAL APPLICATIONS
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However , no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. PACKAGE DESCRIPTION MSOP (MSE16) 0608 REV A 0.53 p 0.152 (.021 p .006) SEATING PLANE 0.18 (.007) 1.10 (.043) MAX 0.17 – 0.27 (.007 – .011) TYP 0.86 (.034) REF 0.50 (.0197) BSC 16151413121110 12345678 1 8 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) 0o – 6o TYP DETAIL “A” DETAIL “A” GAUGE PLANE 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 0.889 p 0.127 (.035 p .005) RECOMMENDED SOLDER PAD LAYOUT 0.305 p 0.038 (.0120 p .0015) TYP 0.50 (.0197) BSC BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 p 0.102 (.112 p .004) 2.845 p 0.102 (.112 p .004) 4.039 p 0.102 (.159 p .004) (NOTE 3) 1.651 p 0.102 (.065 p .004) 1.651 p 0.102 (.065 p .004) 0.1016 p 0.0508 (.004 p .002) 3.00 p 0.102 (.118 p .004) (NOTE 4) 0.280 p 0.076 (.011 p .003) REF 4.90 p 0.152 (.193 p .006) 16-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1667 Rev A) DETAIL “B” DETAIL “B” CORNER TAIL IS PART OF THE LEADFRAME FEATURE. FOR REFERENCE ONL Y NO MEASUREMENT PURPOSE
0.12 REF
0.35 REF
Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2008 LT 1008 • PRINTED IN USA RELATED PARTS TYPICAL APPLICATION PART NUMBER DESCRIPTION COMMENTS L T1424-5 Isolated Flyback Switching Regulator 5V Output Voltage, No Optoisolator Required L T1424-9 Isolated Flyback Switching Regulator 9V Output, Regulation Maintained Under Light Loads L T1425 Isolated Flyback Switching Regulator with No External Power Devices No Optoisolator or “Third Winding” Required, Up to 6W Output LT C ®1624 Current Mode DC/DC Controller 300kHz Operating Frequency; Buck, Boost, SEPIC Topologies; VIN Up to 36V , SO-8 Package L T1725 General Purpose Isolated Flyback Controller No Optoisolator Required, V IN and VOUT Limited Only by External Power Components L T1737 High Power Isolated Flyback Controller No Optoisolator or “Third Winding” Required, Up to 50W Output L TC1871/L TC1871-1, L TC1871-7 Wide Input Range, No RSENSE TM Current Mode Flyback, Boost and SEPIC Controller Adjustable Switching Frequency, 2.5V ≤ VIN ≤ 36V , Optional Burst Mode® Operation at Light Load L TC1872, L TC1872B SOT-23 Constant-Frequency Current Mode Boost DC/DC Controller 550kHz Switching Frequency, 2.5V to 9.8V VIN Range L T1950 Current Mode PWM Controller C ontroller for Forward, Boost, Flyback and SEPIC Converters from 30W to 300W L TC3803/L TC3803-5 200kHz Flyback DC/DC Controller V IN and VOUT Limited Only by External Components L TC3805/L TC3805-5 Adjustable Frequency Flyback Controller V IN and VOUT Limited Only by External Components L TC3806 Synchronous Flyback Controller High Effi ciency (89%); Multiple Output with Excellent Cross Regulation L T3825 Isolated No-Opto Synchronous Flyback Controller V IN 16V to 75V Limited by External Components, Up to 80W , Current Mode Control L T3837 Isolated No-Opto Synchronous Flyback Controller V IN 4.5V to 36V Limited by External Components, Up to 60W , Current Mode Control L TC3872 No R SENSE Boost Controller 550kHz Fixed Frequency, 2.75V ≤ V IN ≤ 9.8V , ThinSOTTM or DFN Package L TC3873/L TC3873-5 No RSENSE Constant-Frequency Boost/Flyback/ SEPIC Controller VIN and VOUT Limited by External Components, 200kHz Frequency, ThinSOT or Burst Mode is a registered trademark of Linear Technology Corporation. No RSENSE and ThinSOT are trademarks of Linear Technology Corporation. 9V to 30VIN, +5V/–5V OUT Isolated Flyback Converter SHDN/UVLO TC SS SW VC GND BIAS L T3573
3573 TA11
28.7k 10k VIN 9V TO 30V VIN 3:1:1:1 357k 51.1k 10μF L1A 63μH 6.04k 80.6k VOUT+ +5V , 350mA COM VOUT– –5V , 350mA 47μF 47μF L1B 7μH L1C 7μH 2700pF 23.7k 4.7μF 10nF *OPTIONAL THIRD WINDING FOR >24V OPERATION T1: W ÜRTH ELEKTRONIK 750310564 L1D 7μH 0.22 μF TEST RILIM RFB RREF