LT3999 Low Noise, 1A, 1MHz Push-Pull DC/DC Driver with Duty Cycle Control FEATURES DESCRIPTION Wide Input Operating Range: 2.7V to 36V n Dual 1A Switches with Programmable Current Limit n Programmable Switching Frequency: 50kHz to 1MHz n Frequency Synchronization Up to 1MHz n ∆V Compensation Using Duty Cycle Control IN n Low Noise Topology n Programmable Input Over and Undervoltage Lockout n Cross Conduction Prevention Circuitry n Programmable Soft-Start n Low Shutdown Current: <1µA n10-Lead MSOP and DFN Packages The LT®3999 is a monolithic, high voltage, high frequency DC/DC transformer driver providing isolated power in a small solution footprint. n The LT3999 has two 1A current limited power switches that switch out of phase. The duty cycle is programmable to adjust the output voltage. The switching frequency is programmed up to 1MHz and can be synchronized to an external clock for more accurate placement of switcher harmonics. The input operating range is programmed with the precision undervoltage and overvoltage lockouts. The supply current is reduced to less than 1µA during shutdown. A user-defined RC time constant provides an adjustable soft-start capability by limiting the inrush current at start-up. APPLICATIONS n n n n n n Low Noise Isolated Supplies Medical Instrument and Safety Distributed Power Multiple Output Supplies Positive-to-Negative Supplies Noise Immunity in Data Acquisition, RS232 and RS485 The LT3999 is available in a 10-lead MSOP and 3mm × 3mm DFN package with exposed pad. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION LT3999 Line Regulation with Duty Cycle Control 12V to 12V, 10W Low Noise Isolated DC/DC Converter 16 10µF 16V VIN 15.3µH SYNC 255k SWA UVLO • • OVLO/DC RDC 10k • LT3999 15.8k SWB RT 10µF 16V VOUT 12V 0.8A • 3999 TA01a ILIM/SS 28k 500kHz RBIAS 0.1µF 49.9k 15 OUTPUT VOLTAGE (V) VIN 12V 14 13 IOUT = 200mA IOUT = 400mA 12 IOUT = 800mA 11 10 9 GND 8 10 11 12 13 14 15 16 INPUT VOLTAGE (V) 17 18 3999 TA01b 3999fa For more information www.linear.com/LT3999 1 LT3999 ABSOLUTE MAXIMUM RATINGS (Note 1) SWA, SWB.................................................. –0.3V to 80V VIN, UVLO................................................... –0.3V to 60V OVLO/DC, SYNC .......................................... –0.3V to 8V Operating Junction Temperature Range (Note 2) LT3999E............................................. –40°C to 125°C LT3999I.............................................. –40°C to 125°C LT3999H............................................. –40°C to 150°C LT3999MP.......................................... –55°C to 150°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) MSOP................................................................ 300°C PIN CONFIGURATION TOP VIEW TOP VIEW SWA RBIAS VIN UVLO OVLO/DC 1 2 3 4 5 11 GND 10 9 8 7 6 SWB ILIM/SS SYNC RT RDC MSE PACKAGE 10-LEAD PLASTIC MSOP θJA = 40°CW, θJC = 10°CW EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB SWA 1 RBIAS 2 VIN 3 UVLO 4 OVLO/DC 5 10 SWB 11 GND 9 ILIM/SS 8 SYNC 7 RT 6 RDC DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN θJA = 43°C/W, θJC = 5.5°C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3999EMSE#PBF LT3999EMSE#TRPBF LTGKR 10-Lead Plastic MSOP –40°C to 125°C LT3999IMSE#PBF LT3999IMSE#TRPBF LTGKR 10-Lead Plastic MSOP –40°C to 125°C LT3999HMSE#PBF LT3999HMSE#TRPBF LTGKR 10-Lead Plastic MSOP –40°C to 150°C LT3999MPMSE#PBF LT3999MPMSE#TRPBF LTGKR 10-Lead Plastic MSOP –55°C to 150°C LT3999EDD#PBF LT3999EDD#TRPBF LGKQ 10-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C LT3999IDD#PBF LT3999IDD#TRPBF LGKQ 10-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on nonstandard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 2 3999fa For more information www.linear.com/LT3999 LT3999 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 15V PARAMETER CONDITIONS MIN TYP MAX UNITS Input Supply and Shutdown VIN Minimum Operating Voltage 2.7 l VIN Overvoltage Lockout Internal, Rising VIN Supply Current (Note 3) VIN Shutdown Current VUVLO = 0.3V l 36 UVLO Threshold (Rising) l 1.15 UVLO Hysteresis UVLO Pin Current 42 VUVLO = 1.25V l 1.15 OVLO/DC Hysteresis 0.1 1 μA 1.25 1.35 V mV 10 100 nA 1.25 1.35 V 125 VOVLO/DC = 1.25V V mA 125 OVLO/DC Threshold (Rising) OVLO/DC Pin Current 40 4.3 V 10 mV 100 nA Power Switches (SWA, SWB) Switch Saturation Voltage ISW = 1A Switch Current Limit Internal Default 350 l 1.0 Non Overlap Time Switch Base Drive Current ISW = 1A 1.4 mV 1.7 A 70 ns 35 mA Oscillator/Sync Switching Frequency RT = 316k RT = 49.9k RT = 12.1k l Synchronization Frequency Range 280 50 300 1000 100 320 kHz kHz kHz 1000 kHz SYNC Voltage Threshold 1.5 V SYNC Pin Input Resistance 200 kΩ ILIM/SS SWA and SWB Current Limit RILIM/SS = 43.2k l 0.4 ILIM/SS Pin Current 0.5 0.6 10 A μA Duty Cycle Switch Duty Cycle OVLO/DC = 0.8V, RDC = 24.3k, RT = 49.9k OVLO/DC = 0.612V, RDC = 24.3k, RT = 49.9k OVLO/DC = 0.3V, RDC = 24.3k, RT = 49.9k 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 the device reliability and lifetime. Note 2: The LT3999E is guaranteed to meet performance specifications from 0°C to 125°C junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization, and correlation with statistical process controls. The LT3999I Is guaranteed over the –40°C to 125°C operating junction temperature range. The LT3999H is guaranteed over the full –40°C to 150°C operating junction temperature range. The LT3999MP is 100% tested and guaranteed over the –55°C to 150°C junction temperature range. High junction temperatures degrade operating lifetimes; operating lifetime is derated for junction temperatures greater than 125°C. l 22 20 25 48 30 % % % Note 3: Supply current specification does not include switch drive currents. Actual supply currents will be higher. 3999fa For more information www.linear.com/LT3999 3 LT3999 TYPICAL PERFORMANCE CHARACTERISTICS VIN Shutdown Current Switching Frequency 1.5 1.0 VCESAT vs Switch Current 400 400 375 350 350 300 SWITCH VCESAT (mV) 2.0 FREQUENCY (kHz) SHUTDOWN CURRENT (µA) 2.5 325 300 275 250 0.5 225 0 –50 –25 0 0 Switch Leakage Current 1800 400 300 200 1600 CURRENT LIMIT (mA) SWITCH CURRENT (µA) SWITCH VCESAT (mV) Switch Current Limit 2000 2.5 500 2.0 1.5 1.0 0.5 0 1.35 1.35 OVLO PIN VOLTAGE (V) UVLO PIN VOLTAGE (V) UVLO FALLING 1.10 1.05 25 50 75 100 125 150 TEMPERATURE (°C) 1.20 OVLO FALLING 1.15 1.10 1.05 1.00 0.95 0.95 25 50 75 100 125 150 TEMPERATURE (°C) OVLO RISING 1.25 1.00 0 0 3999 G06 1.30 UVLO RISING 1.20 0.90 –50 –25 RILIM/SS = 43.2k 600 OVLO Threshold Voltage 1.40 1.15 800 3999 G05 UVLO Threshold Voltage 1.25 RILIM/SS = 80.6k 1000 0 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 1.40 1.30 1200 200 0 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) RILIM/SS = OPEN 1400 400 3999 G04 0.90 –50 –25 3999 G07 4 0 100 200 300 400 500 600 700 800 900 1000 SWITCH CURRENT (mA) 3999 G03 3.0 SWITCH CURRENT = 1A 0 100 3999 G02 Switch VCESAT 100 –50 –25 150 0 25 50 75 100 125 150 TEMPERAURE (°C) 3999 G01 600 200 50 200 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 250 0 25 50 75 100 125 150 TEMPERATURE (°C) 3999 G08 3999fa For more information www.linear.com/LT3999 LT3999 TYPICAL PERFORMANCE CHARACTERISTICS Soft-Start (ILIM/SS) Current Switch Duty Cycle 14 40 35 12 11 DUTY CYCLE (%) SOFT-START CURRENT (µA) 13 10 9 8 7 6 25 20 15 5 4 –50 –25 30 0 25 50 75 100 125 150 TEMPERATURE (°C) 10 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3999 G10 3999 G09 PIN FUNCTIONS SWA, SWB (Pin 1, Pin 10): SWA and SWB pins are the open-collector nodes of the power switches. These pins drive the transformer and are connected to the outer terminals of the center tapped transformer. Large currents flow through these pins so keep PCB traces short and wide. RBIAS (Pin 2): The RBIAS pin sets the bias current of the power switches (SWA and SWB). Connect the pin to a 49.9k resistor to GND. VIN (Pin 3): The VIN pin is the main supply pin for the switch driver and internal regulator. Short duration, high current pulses are produced during the turn on and turn off of the power switches. Connect a low ESR capacitor of 4.7µF or greater. UVLO (Pin 4): The UVLO pin has a precision threshold with hysteresis to implement an accurate VIN undervoltage lockout. The UVLO function disables switching and sets the part into a low current shutdown mode. Connect the UVLO pin directly to VIN or to a resistor divider string. OVLO/DC (Pin 5): The OVLO/DC pin has a precision threshold with hysteresis to implement an accurate VIN overvoltage lockout. The OVLO function disables the switching. Connect OVLO/DC pin to ground to disable the function or to a resistor divider string to program the duty cycle. RDC (Pin 6): The RDC pin is the duty cycle control pin. A resistor to ground sets the duty cycle. If unused leave the pin floating or connect to the OVLO/DC pin. RT (Pin 7): The RT pin sets the switching frequency of the power switches. SYNC (Pin 8): The SYNC pin synchronizes the part to an external clock. Set the internal oscillator frequency below the external clock frequency. Synchronizing the clock to an external reference is useful for creating more stable positioning of the switcher voltage or current harmonics. Connect the SYNC pin to ground if not used. ILIM/SS (Pin 9): The ILIM/SS pin sets a threshold level for the cycle by cycle maximum switch current. Implement soft-start with a capacitor, CSS, placed on this pin to ground. An internal current source charges the capacitor. The RILIM, CSS time constant sets the soft-start time and ramps the maximum switch current threshold at start-up. If the ILIM/SS function is not used, float this pin and the current limit will default to the internal limit. GND (Pin 11): The ground pin is the exposed pad of the package. Solder the exposed pad directly to the ground plane. 3999fa For more information www.linear.com/LT3999 5 LT3999 BLOCK DIAGRAM • VIN CIN T1 • D1 VOUT • • D2 3 1 VIN RA2 4 UVLO BANDGAP + + SWB LINEAR REGULATOR INTERNAL BIAS – RA1 10 SWA + + 5 OVLO/DC SWITCH CONTROL – SWITCH A RB + 2 RBIAS SWITCH B + OSCILLATOR – + – DUTY CYCLE CONTROL + RSENSE RDC 6 RT SYNC 8 RDC 6 RBIAS 7 RT + – + – – GND ILIM/SS 11 9 RILIM 3999 BD CSS 3999fa For more information www.linear.com/LT3999 LT3999 OPERATION Overview Current Limit and Soft-Start The LT3999 is a monolithic isolated push-pull DC transformer driver. It includes functions such as duty cycle control, soft-start and protection features. The LT3999 ILIM/SS pin programs the cycle-by-cycle switch current limit and the soft-start time. A resistor on the ILIM/SS pin sets the current limit. A capacitor on the pin in conjunction with the resistor sets the soft-start time. Push-Pull Topology In a push-pull topology, a pair of switches operating out of phase generate a square wave voltage pulse on the primary side of a center tapped transformer. The diodes on the secondary side rectify the voltage and generate the output voltage. This voltage is simply VIN times the transformer turns ratio. Duty Cycle Control The LT3999 duty cycle control provides, to a degree, line regulation. The duty cycle is programmed by a resistor on the RDC pin and the OVLO/DC voltage. By making the OVLO/DC voltage a function of VIN the duty cycle will adjust with varying VIN thereby keeping VOUT constant. This feature is useful in cases where an LDO is used to post regulate the output of the LT3999. By pseudo regulating the output with the duty cycle control the power dissipation in the LDO is minimized. Leaving the RDC pin floating or connecting it to the OVLO/ DC pin disables the duty cycle function and the LT3999 operates at close to 50% duty cycle. When the programmed current limit is reached the switch is immediately turned off and remains off for the remainder of the cycle. Leaving the ILIM/SS pin unconnected will disable the programmable current limit and the LT3999 will default to its internal current limit. The soft-start function ramps the maximum switch current over the programmed soft-start time. The purpose of the soft-start is to reduce inrush current from the input supply. Other Features The LT3999 protection features include overvoltage lockout (OVLO), undervoltage lockout (UVLO) and thermal shutdown. The OVLO function is programmed with the OVLO/DC pin. Switching is disabled during an OVLO event. An internal overvoltage lockout on the VIN pin is also provided to protect the LT3999. The UVLO function is programmed with the UVLO pin. Switching is disabled during a UVLO event. The UVLO pin is also used to put the LT3999 into a low quiescent shutdown state. At a junction temperature above the operating temperature range the thermal shutdown function turns off both switches. 3999fa For more information www.linear.com/LT3999 7 LT3999 APPLICATIONS INFORMATION Switching Frequency Oscillator Sync The LT3999 drives two output power switches out of phase, thus the oscillator frequency is two times the actual switching frequency of each power switch. The choice of switching frequency is a trade-off between power efficiency and the size of capacitive and inductive storage components. In applications where a more precise frequency is desired to accurately place high frequency harmonics, the LT3999 oscillator can be synchronized to an external clock. Set the internal oscillator frequency 10% to 50% lower than the external sync frequency. The switching frequency is one-half the sync frequency. Operating at low switching frequency reduces the switching losses (transient losses) and consequently improves the power converter efficiency. However, the lower switching frequency requires greater inductance for a given amount of ripple current, resulting in a larger design footprint and higher cost. Drive the SYNC pin with a 2V or greater square wave. The rising edge of the sync square wave will initiate clock discharge. If unused, connect the SYNC pin to ground. The LT3999 switching frequency is set in the range of 50kHz to 1MHz. The value of RT for a given operating frequency is chosen from Table 1 or from the following equation: Table 1. Recommended 1% Standard Values RT 316kΩ 158kΩ 76.8kΩ 49.9kΩ 36.5kΩ 28kΩ 22.6kΩ 19.1kΩ 16.2kΩ 14kΩ 12.1kΩ fSW 50kHz 100kHz 200kHz 300kHz 400kHz 500kHz 600kHz 700kHz 800kHz 900kHz 1000kHz 1 R T (kΩ) = – 70ns • 3.25 •1010 2 • fSW Duty Cycle To run the LT3999 at full duty cycle leave the RDC pin unconnected. Variations in VIN are, to a first order, compensated with the LT3999 duty cycle control function. The duty cycle function is implemented with a resistor divider on VIN connected to the OVLO/DC pin and a resistor to ground on the RDC pin. Use the following formula to calculate the RDC resistor or duty cycle: Duty Cycle (DC) = RDC = VIN • 1.25 •RDC RB VIN • •R T • 4 R A +RB RB •R T •DC • 4 R A +RB 1.25 where RA and RB are the resistors from the VIN to OVLO/ DC resistor divider and RT is the frequency setting resistor. See Figure 1. Setting the OVLO/DC pin to be 0.612V at the nominal VIN voltage yields good line regulation over a wide input range. The duty cycle refers to the duty cycle of the individual switch. Normally each switch operates at close to 50% duty cycle. 8 3999fa For more information www.linear.com/LT3999 LT3999 APPLICATIONS INFORMATION Soft-Start and Current Limit VIN The LT3999 soft-start ramps the peak switch current over a time programmed by either a capacitor or a resistor and capacitor on the ILIM/SS pin. VIN RA RB RA2 UVLO OR OVLO/DC UVLO RA1 OVLO/DC When programming the soft-start time with a capacitor only the soft-start time is calculated with the following formula: RB 3999 F01 Figure 1. Precision UVLO and OVLO Resistor Divider tSS (ms) = CSS • 80 where CSS is in µF. The current limit defaults to the internally set value because there is no resistor on the pin. When programming the soft-start time with a resistor and capacitor on the ILIM/SS pin the soft-start time is calculated with the following formula: τ = RC Resistors are chosen by first selecting RB. Then calculate RA with the following formula: V R A =RB TH – 1 1.25V where VTH is the VIN referred voltage at which the supply is enabled (UVLO) or disabled (OVLO/DC). where 3τ will be 95% of the maximum current. Transformer Design The cycle-by-cycle current limit of the LT3999 is set with a resistor on the ILIM/SS pin. Use the following formula to calculate the value of the resistor: Table 3 lists recommended center tapped transformers for a variety of input voltage, output voltage and power combinations. These transformers will yield slightly high output voltages so that they can accommodate an LDO regulator on the output. RILIM (kΩ) = ILIM • 86.4 OVLO/DC and UVLO The UVLO pin has a precision voltage threshold with hysteresis to enable the LT3999. The pin is typically connected to VIN through a resistor divider; however, it can be directly connected to VIN. The OVLO/DC pin has a precision voltage threshold with hysteresis to disable the LT3999 switching operation. The pin is typically connected to VIN through a resistor divider. The OVLO/DC pin can be directly connected to GND to disable the function. It is possible to use two separate resistor divider strings for OVLO/DC and UVLO pins or combine them together and use one resistor divider string to drive both pins. See Figure 1. If your application is not listed, the LTC Applications group is available to assist in the choice and/or the design of the transformer. In the design/selection of the transformer the following characteristics are critical and should be considered: Table 3. Recommended Center Tapped Transformers NOMINAL INPUT VOLTAGE (V) NOMINAL OUTPUT VOLTAGE (V) OUTPUT POWER (W) PART NUMBER 5 5 5 Coilcraft PA6383 5 12 1 Coilcraft PA6381 5 12 3 Cooper Bussmann CTX02-19064 12 12 10 Coilcraft PA6384 24 24 20 Cooper Bussmann CTX02-19061 3999fa For more information www.linear.com/LT3999 9 LT3999 APPLICATIONS INFORMATION Turns Ratio Winding Resistance The turns ratio of the transformer determines the output voltage. The following equation is used as a first pass to calculate the turns ratio: Resistance in either the primary or secondary winding reduces overall efficiency and degrades load regulation. If efficiency or load regulation is unsatisfactory, verify that the voltage drops in the transformer windings are not excessive. NS VOUT + VF = NP 2 ( VIN – VSW ) DC Capacitors where VF is the forward voltage of the output diode, VSW is the voltage drop across the internal switches (see the Typical Performance curves) and DC is the duty cycle. Sufficient margin should be added to the turns ratio to account for voltage drops due to transformer winding resistance. Magnetizing Current The magnetizing inductance of the transformer causes a ripple current that is independent of load current. This ripple current is calculated by: ∆I= VIN •DC fSW •LM where ∆I and LM are primary ripple current and magnetizing inductance referred to the primary side of the transformer, respectively. Increasing the transformer magnetizing inductance, LM, reduces the ripple current. The ripple current formula shows the effect of the switching frequency on the magnetizing inductance. Setting the LT3999 at high switching frequency reduces the ripple current for the same magnetizing inductance. Therefore, it is possible to reduce the transformer turns and still achieve low ripple current. This helps to reduce the power converter footprint as well. The transformer magnetizing inductance should be designed for the worst-case duty cycle and input line voltage combination. A good rule of thumb is to set the primary current ripple amplitude 10% to 30% of the average primary current, IP: IP = POUT VIN • eff In applications with full duty cycle operation, the input supply current is approximately constant. Therefore, large input “hold-up type” capacitors are not necessary. A low value (>4.7µF), low ESR ceramic will be adequate to filter high frequency noise at the input. The output capacitors supply energy to the output load only during switch transitions. Therefore, large capacitance values are not necessary on the output. Transformer winding capacitance between the isolated primary and secondary has parasitic currents that can cause noise on the grounds. Providing a high frequency, low impedance path between the primary and secondary gives the parasitic currents a local return path. A 2.2nF, 1kV ceramic capacitor is recommended. Optional LC Filter An optional LC filter, as shown on the Typical Application on the first page of this data sheet, should be included if ultralow noise and ripple are required. It is recommended that the corner frequency of the filter should be set a decade below the switching frequency so that the switch noise is attenuated by a factor of 100. For example, if the fOSC = 100kHz, then fCORNER = 10kHz where: fCORNER = 1 2 • π LC Switching Diode Selection A fast recovery, surface mount diode such as a Schottky is recommended. The proximity of the diodes to the transformer outputs is important and should be as close as possible with short, wide traces connecting them. where POUT is the output power of the converter and eff is the converter efficiency, typically around 85%. 10 3999fa For more information www.linear.com/LT3999 LT3999 APPLICATIONS INFORMATION Output Voltage Regulation The junction temperature is computed as: The output voltage of the DC transformer topology is unregulated. Variations in the input voltage will cause the output voltage to vary because the output voltage is a function of the input voltage and the transformer turn ratio. Also, variations in the output load will cause the output voltage to change because of circuit parasitics, such as the transformer DC resistance and power switch on resistance. If regulation is necessary, a post regulator such as a linear regulator can be added to the output of the supply. See the Typical Applications for examples of adding a linear regulator. TJ = TAMB + PD • θJA Power Consideration The current derived from the VIN pin and the SWA and SWB switching currents are the sources of the LT3999 power dissipation. The power dissipation is the sum of: where: PD = PVIN + PVCESAT + PSW and θJA is the package thermal resistance. Layout Consideration Check List The following is a list of recommended layout considerations: • Locate the bypass capacitor on the VIN pin of the transformer close to the transformer. • Create a solid GND plane, preferably on layer two of the PCB. • Use short wide traces to connect to the transformer. 1)The quiescent current and switch drive power dissipation: • The transformer and PCB routing should be carefully designed to maximize the symmetry between two switching half cycles. I •DC PVIN = VIN SW + 4mA 30 • Solder the LT3999 exposed pad to the PCB. Add multiple vias to connect the exposed pad to the GND plane. where ISW is the average switch current. More Help 2)The conducting power dissipation of the switches during on state: AN70: “A Monolithic Switching Regulator with 100mV Output Noise” contains much information concerning applications and noise measurement techniques. PVCESAT = VCESAT • ISW • 2DC where DC is the duty cycle and VCESAT is the collector to emitter voltage drop during the switch saturation. 3)The dynamic power dissipation due to the switching transitions: PSW = VIN • ISW • fOSC • (tr + tf) where tr and tf are the rise and fall times. 3999fa For more information www.linear.com/LT3999 11 LT3999 TYPICAL APPLICATIONS 30V to 12V, 10W Push-Pull DC Transformer VIN 30V CIN 10µF 50V VIN R1 499k SYNC SWA UVLO R2 19.1k LT3999 • • • SWB ILIM/SS RBIAS RBIAS 49.9k VOUT 12V COUT 0.8A 10µF 16V D2 RT C1 0.1µF • OVLO/DC RDC RT 28k 500kHz L1 OPTIONAL D1 T1 3999 TA02 D1, D2: DIODES INC. B260 L1: COILCRAFT M56132-153 T1: COOPER BUSSMANN CTX02-19062 GND 5V to 5V, 4W Low Part Count Push-Pull DC Transformer VIN 5V CIN 47µF 10V VIN UVLO D1 T1 SWA SYNC • • • • VOUT 5V COUT 0.8A 10µF 10V OVLO/DC LT3999 RDC D2 RT ILIM/SS RT 12.1k 1MHz RBIAS 49.9k RBIAS SWB 3999 TA03 D1, D2: CENTRAL SEMI. CMSH1-20M T1: COILCRAFT PA6383 GND 10V-15V to ±12V, 200mA Isolated Switching Regulator VIN 10V TO 15V CIN 10µF 100V R1 715k VIN SYNC R2 36.5k SWA UVLO ILIM/SS 12 CSS 0.01µF RBIAS 49.9k RBIAS • • D2 • • D3 SWB RT RDC 13.3k R4 39k LT3999 RDC RT 12.1k 1MHz C3 180pF OVLO/DC R3 66.5k D1 T1 GND D4 D1-D4: CENTRAL SEMI. CMSH1-200HE L1, L2: COILCRAFT XFL3012-393MEG T1: WÜRTH 750314781 L1 39µH C1 10µF R7 50V 10k 0.01µF L2 39µH C2 10µF 50V SHDN OUT IN LT3065 ADJ REF/BYP SHDN OUT IN ILIM LT3090 SET GND 1M COUT1 10µF 25V VOUT 12V 200mA R8 52.3k COUT2 10µF 25V –VOUT –12V R6 200mA 10k R10 243k 3999 TA04 3999fa For more information www.linear.com/LT3999 LT3999 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MSE Package 10-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1664 Rev I) BOTTOM VIEW OF EXPOSED PAD OPTION 1.88 ±0.102 (.074 ±.004) 5.10 (.201) MIN 1 0.889 ±0.127 (.035 ±.005) 1.68 ±0.102 (.066 ±.004) 0.05 REF 10 0.305 ± 0.038 (.0120 ±.0015) TYP RECOMMENDED SOLDER PAD LAYOUT 3.00 ±0.102 (.118 ±.004) (NOTE 3) DETAIL “B” CORNER TAIL IS PART OF DETAIL “B” THE LEADFRAME FEATURE. FOR REFERENCE ONLY NO MEASUREMENT PURPOSE 10 9 8 7 6 DETAIL “A” 0° – 6° TYP 1 2 3 4 5 GAUGE PLANE 0.53 ±0.152 (.021 ±.006) DETAIL “A” 0.18 (.007) 0.497 ±0.076 (.0196 ±.003) REF 3.00 ±0.102 (.118 ±.004) (NOTE 4) 4.90 ±0.152 (.193 ±.006) 0.254 (.010) 0.29 REF 1.68 (.066) 3.20 – 3.45 (.126 – .136) 0.50 (.0197) BSC 1.88 (.074) SEATING PLANE 0.86 (.034) REF 1.10 (.043) MAX 0.17 – 0.27 (.007 – .011) TYP 0.50 (.0197) BSC 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 6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL NOT EXCEED 0.254mm (.010") PER SIDE. 0.1016 ±0.0508 (.004 ±.002) MSOP (MSE) 0213 REV I 3999fa For more information www.linear.com/LT3999 13 LT3999 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699 Rev C) 0.70 ±0.05 3.55 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.38 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 ±0.10 (4 SIDES) R = 0.125 TYP 6 0.40 ± 0.10 10 1.65 ± 0.10 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.35 × 45° CHAMFER PIN 1 TOP MARK (SEE NOTE 6) 0.200 REF 0.75 ±0.05 0.00 – 0.05 5 1 (DD) DFN REV C 0310 0.25 ± 0.05 0.50 BSC 2.38 ±0.10 (2 SIDES) BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 14 3999fa For more information www.linear.com/LT3999 LT3999 REVISION HISTORY REV DATE DESCRIPTION A 04/15 Corrected pin assignments PAGE NUMBER Revised schematics 5 13, 16 3999fa 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. For more information www.linear.com/LT3999 15 LT3999 TYPICAL APPLICATION 5V to 12V, 1W Low Power Push-Pull DC Transformer VIN 5V CIN 10µF 10V VIN R1 261k SYNC SWA UVLO R2 100k LT3999 ILIM/SS RILIM 40.3k • • COUT 2.2µF 16V RBIAS 49.9k RBIAS VOUT 12V 0.08A D1B RT CSS 0.1µF • OVLO/DC RDC RT 12.1k 1MHz D1A T1 • GND SWB 3999 TA05 D1, D2: VISHAY BAT54C T1: COOPER BUSSMANN CTX02-19065R RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT3439 Slew Rate Controlled Ultralow Noise 1A Isolated DC/DC Transformer Driver VIN: 2.7V to 17.5V, IQ (Supply) = 12mA, ISD < 12mA, SO-16, Low Noise: <100mVP-P, Independent Control of Switch Voltage and Current Slew Rates LT1533 Slew Rate Controlled Ultralow Noise 1A Switching Regulator VIN: 2.7V to 23V, IQ (Supply) = 12mA, ISD < 12mA, SO-16, Low Noise: <100mVP-P, Independent Control of Switch Voltage and Current Slew Rates LT1683 Slew Rate Controlled Ultralow Noise Push-Pull Controller VIN: 2.7V to 20V, IQ (Supply) = 25mA, ISD < 24mA, SSOP-20, Low Noise: <200mVP-P, Independent Control of Switch Voltage and Current Slew Rates LT1738 Slew Rate Controlled Ultralow Noise DC/DC Controller VIN: 2.7V to 20V, IQ (Supply) = 12mA, ISD < 24mA, SSOP-20, Greatly Reduced Conducted and Radiated EMI, Independent Control of Switch Voltage and Current Slew Rates 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LT3999 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LT3999 3999fa LT 0415 REV A • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2014