LX13088 ® TM Dual 1A Step-Down Converters P RODUCTION D ATASHEET DESCRIPTION synchronized to an external clock. With the E/S input held low, the LX13088 draws less than 10uA. Both converters have controlled soft start, in addition to power up sequencing. In the start-up sequence, the output of converter 1 is designed to precede the output of converter 2. Power On Reset function is provided by means of an open-drain output at the POR pin. The Power On Reset function monitors the voltages at the VMON, FB1 and FB2 pins, and pulls low if any of these voltages drop below the stated POR threshold. The POR is internally deglitched and provides a delayed recovery and reset time. The LX13088 provides peak over current protection, short circuit protection and thermal shutdown. Discharge-BeforeTurn-On discharges the outputs completely before soft starting to always bring them up in the proper sequence at start up or after a POR event. • Outputs can be set from 1V to 3.6V @ 1A • No Rectifier Diode required • 1.3MHz Switching • 180° Phase Shifted Switching • Optional External Clocking (2x clock required) • Light load Pulse Skipping • Enable/Sleep state • Internal Soft Start • Open-drain Power On Reset Monitors Input and Outputs • Discharge Before-Turn-On • Peak Over-Current Protection • Short Circuit Protection • Over Temperature Shutdown WWW . Microsemi .C OM The LX13088 is a highly integrated dual output voltage regulator ideal for low power applications that require minimal board space. The two current mode buck converters include integrated high side control switches, synchronous rectifiers, and internal compensation. The outputs of each converter are both rated for up to 1A, and the output voltages are adjustable using external resistive dividers. The LX13088 step down converters operate at 1.3MHz fixed switching frequency under normal load, reducing external output filter component values and size. Under light load conditions, the converters operate in a pulse-skipping mode for improved efficiency. The LX13088 incorporates out of phase switching, where converter 2 switches 180° out of phase from converter 1 in order to minimize the input ripple effects. The controller also features an E/S pin that provides an enable input function, or allows the converter to be KEY FEATURES APPLICATIONS • Hard Disk Drives • Set- Top Boxes IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com Product Highlight TA (°C) 0 to +70 LD THERMAL DATA Plastic 3x3 mm DFN 10-pin θJA = 33 °C/W RoHS Compliant / Pb-free THERMAL RESISTANCE-JUNCTION TO AMBIENT LX13088CLD Junction Temperature Calculation: TJ = TA + (PD x θJA). The θJA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow. Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX13088CLD-TR) Copyright © 2010 Rev. 1.1, 2010-06-08 LX13088 PACKAGE ORDER INFO Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 1 LX13088 ® TM Dual 1A Step-Down Converters P RODUCTION D ATASHEET ABSOLUTE MAXIMUM RATINGS PACKAGE PIN OUT WWW . Microsemi .C OM PVIN, AVIN to AGND, PGND...................................................................... -0.3 to +7.0 V SW1 and SW2 to AGND, PGND .................................................. PGND -2V to xVIN+2V All other pins to AGND.................................................................... -0.3V to xVIN + 0.3V Operating Junction Temperature Range .......................................................... 00C to 1500C Storage Temperature Range..........................................................................–650C to 1500C 0 Package Peak Temp. for Solder Reflow (40 seconds maximum exposure) .. 260°C (+0 -5) C Notes: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of specified terminal. PGND must be wired to AGND externally. LD PACKAGE (Top View) Marking 3088 Date/Lot Code MSC RoHS / Pb-free 100% Matte Tin Finish FUNCTIONAL PIN DESCRIPTION Name Pin # Description 1 Feedback from VO2. Connect voltage divider to the load side of VO2 output inductor-capacitor filter. AVIN 2 Analog Input. Input to power the internal circuitry of the device, connect to PVIN through a 10Ω resistor and bypass through a 1μF ceramic capacitor between this pin and PGND, as close to the LX13088 as possible. PVIN 3 Control MOSFET switch power inputs. Connect a 10µF ceramic capacitor between this pin and PGND, as close to the LX13088 as possible. SW2 4 Converter 2 synchronous buck switching output. Connect to VO2 inductor. PGND 5 Power Ground Connection. Synchronous rectifier MOSFET source. Provide a star connection between this pin, VO1, VO2 filter capacitor returns, VIN input capacitor return, and AGND. Keep the star connection as close to the LX13088 IC as possible. SW1 6 Converter 1 synchronous buck switching output. Connect to VO1 inductor. E/S 7 Enable/Synchronization. Pulling this pin high statically enables the LX13088 and pulling the pin low statically will shut down the LX13088. Applying a pulse to this pin will synchronize SW1 and SW2 switching frequency to ½ the external clock frequency. POR 8 Power On Reset output pin. Monitors FB1, FB2 output voltage levels and VIN. POR is pulled low if an output voltage droop is detected on FB1 or FB2 or VIN, and is Hi-Z during normal operation. VMON 9 Voltage Monitor – Supervisor for one external voltage (could be input voltage). The POR output is triggered if this output falls below the VMON threshold. FB1 10 Feedback from VO1. Connect voltage divider to the load side of VO1 output inductor-capacitor filter. AGND PAD Copyright © 2010 Rev. 1.1, 2010-06-08 Analog Ground. Connect the exposed pad on the bottom of the package to the GND plane for a thermal heat sink. Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 2 LX13088 FB2 LX13088 ® TM Dual 1A Step-Down Converters P RODUCTION D ATASHEET ELECTRICAL CHARACTERISTICS Parameter Symbol Test Conditions / Comment Min Typ Max Units 4.5 5.0 5.5 V 3.0 3.5 4.0 V 200 300 400 mV 0.01 0.6 1 mA 0.1 10 µA Input Circuitry Operating Input Voltage VVIN Under Voltage Lockout VVIN-UVLO VVIN Rising UVLO Hysteresis TA = 25°C; not switching; 1.2V = VFB1 = VFB2 Input Supply Current WWW . Microsemi .C OM Unless otherwise specified, the following specifications apply over the operating ambient temperature of 00C < Temp <700C, and the following test conditions: 4.5 ≤ VVIN ≤ 5 .5V, VPGND = VAGND ; E/S = High (Static) IVIN E/S = low VMON Input VVMON- POR Threshold VMON VVMON Falling (hysteresis = 20mV) 0.97 1.00 1.03 V VVMON = 1.25V -100 0 100 nA VFB1 0.975 1.000 1.025 V ISW1-CT 1.2 1.6 A E/S = static logic high 1.3 MHz TJ = 80°C 275 TJ = 25°C 250 TJ = 80°C 230 TJ = 25°C 200 POR VMON input current IVMON VO1 Output Feedback Voltage Peak Current Limit Threshold PWM Switching Frequency FSW1 Upper FET On Resistance RDSSW1-U mΩ Lower FET On Resistance Soft Start Time RDSSW1-L tSS_FB1 0.5 1 2 ms VFB1-POR FB1 Falling (hysteresis = 2% VFB1) 87 89.5 92 %VFB1 Discharge Complete Threshold VFB1-DCT FB1 level where discharge cycle is terminated 50 75 100 mV VFB2 0.975 1.000 1.025 V ISW2-CT 1.2 1.6 A 1.3 MHz VO2 Output Feedback Voltage Current Limit PWM Switching Frequency Copyright © 2010 Rev. 1.1, 2010-06-08 FSW2 E/S = static logic high Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 3 LX13088 POR Threshold FB1 LX13088 ® TM Dual 1A Step-Down Converters P RODUCTION D ATASHEET ELECTRICAL CHARACTERISTICS Unless otherwise specified, the following specifications apply over the operating ambient temperature of 00C < Temp <700C, and the following test conditions: 4.5 ≤ VVIN ≤ 5 .5V, VPGND = VAGND ; E/S = High (Static) Upper FET On Resistance Symbol Test Conditions / Comment Min Typ TJ = 80°C 240 TJ = 25°C 250 TJ = 80°C 155 TJ = 25°C 150 Max Units RDSSW2-U mΩ Lower FET On Resistance Soft Start Time RDSSW2-L tSS_FB2 0.5 1 2 ms POR Threshold FB2 VFB2-POR FB2 Falling (hysteresis = 2% VFB2) 87 90 92 %VFB2 Discharge Complete Threshold VFB2-DCT FB2 level where discharge cycle is terminated 50 75 100 mV WWW . Microsemi .C OM Parameter E/S E/S Threshold 1.5 VE/S - H V VE/S - L E/S Leakage Current I E/S FE/S - MIN Frequency lock in range FE/S -MAX Shutdown delay tE/S-SHDN 0 < V E/S < VVIN Switching frequency is ½ E/S frequency when externally clocked. Shutdown initiated if logic low is of longer duration than delay. -100 0.6 V 100 nA 1.5 MHz 3.0 2 4 10 µs POR POR Assert Delay Time tPOR_DELAY Fault Flag set to POR pull low POR Release Delay Time tPOR_HOLD Fault Flag reset to POR Hi-Z state POR Low Voltage VPOR_LOW POR sinking 4mA POR High Leakage 25 10 µs 20 30 ms 200 300 mV 0.003 1 µA POR High Level VFB1-ST FB1 rising voltage for FB2 to initiate soft start 87 90 92 %VFB1 Discharge Resistance for SW1 and VO2 15 30 45 Ω 0.90 1 1.1 Power Up Sequencing VO2 Start Threshold Brown Out Discharge SW1, SW2 Discharge Resistance SW1, SW2 Discharge Resistance matching Copyright © 2010 Rev. 1.1, 2010-06-08 RSTOPSW1,2 RSTOP-SW1 / RSTOPSW2 Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 4 LX13088 IPOR_HI LX13088 Dual 1A Step-Down Converters ® TM P RODUCTION D ATASHEET SYSTEM CHARACTERISTICS Parameter Symbol Test Conditions / Comment Min Typ Max Units VO1 Output Line Regulation VO1 ISW1(avg) = 300mA; 4.50V < VVIN < 5.50V Load Regulation VO1 5mA < ISW1(avg) < 1000mA Dynamic Load Response VO1 Transient Response = 500mA step anywhere within 10mA to 1000mA range, ∆I / ∆t = 1A/µs ηVO1 % 0.5 % -5 ISW1(avg) = 1000mA; VO1= 2.5V Efficiency (L1 DCR = 44mΩ) 0.1 ISW1(avg) = 200mA ; VO1= 2.5V ISW1(avg) = 10mA; VO1= 2.5V +5 WWW . Microsemi .C OM Unless otherwise specified, the following specifications apply over the operating ambient temperature of 00C < Temp <700C, and the following test conditions:, 4.5 ≤ VVIN ≤ 5.5V, E/S = High. Configured per application circuit. System Characteristics are closed loop tests that are verified as part of characterization but are not tested in production. %VO 1 87 94 % 82 VO2 Output Line Regulation VO2 ISW2(avg) = 300mA; Load Regulation VO2 Efficiency (L2 DCR = 44mΩ ) ηVO2 4.50V < VVIN < 5.50V 0.1 % 5mA < ISW2(avg) ≤ 1000mA 0.5 % ISW2(avg) = 1000mA; VO2= 1.2V 80 % ISW2(avg) = 200mA; VO2= 1.2V 90 ISW2(avg) = 10mA; VO2= 1.2V 75 % Thermal Shutdown Thermal Shutdown Threshold 160 °C Thermal Shutdown Hysteresis 20 °C LX13088 Copyright © 2010 Rev. 1.1, 2010-06-08 Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 5 LX13088 ® TM Dual 1A Step-Down Converters P RODUCTION D ATASHEET STARTUP SEQUENCING SOFTSTART WWW . Microsemi .C OM Soft start showing converter 1, VOUT1=1.2V at 1A VOUT1=1.2V, VOUT2=2.5V, both outputs loaded at 1A DYNAMIC LOAD EFFICIENCY Copyright © 2010 Rev. 1.1, 2010-06-08 Efficiency for 2.5V and 1.2V output voltages, VIN=5V Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 6 LX13088 VOUT1=1.2V, output 1 load transition from 0.5A to 1A LX13088 TM Dual 1A Step-Down Converters ® P RODUCTION D ATASHEET STARTUP AFTER OUTPUT DISCHARGE SYNCHRONIZATION WWW . Microsemi .C OM Outputs must discharge to <10% before repeat startup Synchronization & out of phase, 3MHz CLK IN at E/S Input CURRENT LIMIT & SHORT CIRCUIT Copyright © 2010 Rev. 1.1, 2010-06-08 Both outputs loaded at 1A, peak to peak output ripple is ~10mV Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 7 LX13088 VOUT1 shorted to ground continuously after normal regulation OUTPUT RIPPLE LX13088 TM ® Dual 1A Step-Down Converters P RODUCTION D ATASHEET FUNCTION BLOCK DIAGRAM WWW . Microsemi .C OM LX13088 Figure 1. Functional Block Diagram Copyright © 2010 Rev. 1.1, 2010-06-08 Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 8 LX13088 TM ® Dual 1A Step-Down Converters P RODUCTION D ATASHEET WWW . Microsemi .C OM TYPICAL APPLICATION Figure 2. Typical Application Circuit LX13088 Copyright © 2010 Rev. 1.1, 2010-06-08 Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 9 LX13088 TM Dual 1A Step-Down Converters ® P RODUCTION D ATASHEET THEORY OF OPERATION POR Under-voltage comparators are provided to monitor the output voltages and the voltage at VMON which could be the input supply voltage. If any of these voltages falls below its POR threshold, the POR open drain output will turn on which pulls the POR pin low. Note that the fault to POR assert delay time is approximately 20µS. If the POR fault condition is cleared, there is a delay of 20ms before the POR output transistor is turned off; when off the POR pin is high Z and may be pulled up high via a resistor. The POR function has built in deglitching. Once the POR is detected, the power supply outputs will be discharged prior to a restart condition, where soft start and power up sequencing will occur. OUTPUT DISCHARGE After the occurrence of a POR situation, and the POR fault condition is immediately cleared, startup and soft start is delayed until the outputs are discharge to <10%. During the discharge phase, the soft start internal reference voltages (REFx) are shorted to ground to quickly discharge it. The output capacitors are discharged via an internal 30Ω pull down switch on each of the SW1 and SW2 pins. When the FBx voltage and the REFx voltage are fully discharged and if there is not an OT condition, the outputs are then allowed to begin the normal soft start power up sequence. During the discharge phase, the control high side and synchronous rectifier MOSFETs are in the high-Z off state. Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 10 LX13088 SOFTSTART The DC-DC converters contain a soft start function that brings the output voltages up via a slowly increasing ramp with any resistive load from open circuit to 1A. The output voltage waveform shall not vary by more than 50mV from a straight line drawn from the initial voltage to the final steady state voltage. During soft start, the peak inductor current shall not exceed 750mA until the output voltage reaches 25% of its final value. Current limit shall be active but not trip during soft start into a rated resistive load. Overshoot voltage during soft start OVER CURRENT AND SHORT CIRCUIT PROTECTION is limited to 1%. The DC-DC converters have over current and short circuit protection. During any mode of operation, any value of load ENABLE AND POWER UP SEQUENCING resistance (including 0 ohms) can be applied to the DC-DC When power is applied at VIN and if the E/S input is asserted outputs instantaneously and held in place indefinitely without (High) or is toggling, the DC-DC converters will enter RUN the switch current exceeding the peak current limit and without mode after a short settling period. If the E/S pin is a static low, the IC suffering any permanent damage or loss of performance. the IC will enter a SLEEP state where it draws very little input The output voltage is allowed to drop under over current or current, less than 10uA. short circuit conditions. Both converters will stop switching if When in RUN mode, if there is no fault condition, the VO1 either one experiences an over current condition for various output of converter 1 will be the first output to begin soft start. cycles. When the reference voltage for FB1 reaches approximately 90% Recovery to output voltage regulation occurs within 10ms of of the final value, the VO2 output of converter 2 will begin soft the instant the loading is reduced to maximum allowable rated start. load; the output voltage shall not exceed the dynamic load excursion limits (+/-5% excursion) upon recovery. Copyright © 2010 Rev. 1.1, 2010-06-08 WWW . Microsemi .C OM DC-DC SWITCHING STEP DOWN CONVERTERS The LX13088 dual DC-DC converters are current mode buck converters with integrated high side switch, synchronous rectifier and internal compensation. They are designed to be stable with a3.3µH inductor value and 10µF to 22µF output capacitor. Both output voltages are resistor divider programmable. The switching frequency of the converter is fixed and the switches turn on at alternating 180° phase intervals. The converters operate in 3 possible modes: continuous mode (CM), discontinuous mode (DM), and pulse skipping mode (PSM). CM is the default mode under normal loading. DM occurs under light loads, where switching still occurs at the programmed frequency. In DM, a zero crossing detector shuts off the synchronous rectifier to prevent reverse rectifier current; this results in a portion of the switch period where neither switch is on. Under very light loads, PSM mode occurs, where switching cycles are skipped if the current demand is low in order to provide better efficiency. LX13088 Dual 1A Step-Down Converters ® TM P RODUCTION D ATASHEET OPERATION The total power dissipated by the LX13088 device, PTOTAL, will be comprised of the power dissipated by the RMS current flowing through the internal high-side FET during the duty cycle D time, by the RMS current flowing through the synchronous rectifier during 1-D time, by the switching or transitioning of the FET, and of the power dissipated by the device supply current. INDUCTOR SELECTION A 3.3µH ±20% inductor is suggested as the internal compensation has been optimized around this inductor value. A 3.3µH is a good compromise, since for an output voltage ranging from VOUT = 1V to VOUT = 4V, loaded at 1A, the LIR or the ratio of inductor ripple current to output load will range from about 20% to 30%, assuming VIN = 5V and the converter switching at 1.3MHz. WWW . Microsemi .C OM E/S DECODER LOGIC The E/S pin serves a dual purpose. It will enable the IC if it detects either a valid clock signal or a static high logic level. A static low logic level for longer than 4µs is determined to be a shutdown signal. The decode logic is shown below. The Oneshot function will produce a logic high output (Clock Detect) as long as the E/S pin is toggling. Clock Detect is used to keep ENABLE high and to select the E/S clock as the system clock. If E/S is a static high (non-toggling) input, the retriggerable one-shot will go low after 4µs; this will set Clk Det low and select the internal oscillator as the system clock. OUTPUT CAPACITOR To ensure stability and good load transient response, use at least a 10µF output capacitor for converter 1, and a 20µF or greater for converter 2. Output ceramics capacitors with low ESR are suitable. SETTING THE OUTPUT VOLTAGE The LX13088 converter’s maximum duty cycle is SYNCHRONIZATION approximately 90%. For a 5V input, 90% duty cycle will be The converters can be synchronized to an external system achieved for an output voltage of about 4V loaded at 1A. clock present at the E/S input pin. During synchronization, the converter’s switching frequency will be ½ the frequency of the To set the output voltage, connect a resistive divider from the external clock, and the two converters will still be 180 degrees out of phase. The lock in frequency for synchronization is output to the FBx pin to signal ground. Note that the feedback specified to be between 1.5MHz to 3MHz, minimum sync pulse voltage is 1.0V. For the desired output voltage VOUT, the upper resistor from VOUT to FB (RUPPER) is calculated by the width is 100ns. following equation: ( T =T + P ×θ TOTAL JA J A Copyright © 2010 Rev. 1.1, 2010-06-08 ) Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 11 LX13088 OVER TEMPERATURE PROTECTION ⎛ VOUT ⎞ If an over temperature fault occurs, the DC-DC converter will R =R ×⎜ − 1⎟ UPPER LOWER ⎝ VFB ⎠ stop switching and the SW# outputs will become high impedance. Note that the temperature fault occurs at a die RLOWER, or the resistor from FBx pin to ground, is selected to be temperature of approximately 160˚C. When the IC cools down, 20kΩ. VFB = 1V, and VOUT is chosen by the designer for the it will attempt to resume switching. If a POR is activated as a given application. result of the OT situation, restart will be subject to the soft start/sequencing routine and will not occur until the OT condition has been corrected. The device junction temperature is a function of the device’s total power dissipation, the junction to ambient thermal resistance, and the ambient temperature: LX13088 Dual 1A Step-Down Converters ® TM P RODUCTION D ATASHEET PACKAGE DIMENSIONS WWW . Microsemi .C OM LD 10-Pin Plastic MLP Dual Exposed Pad D e Dim A A1 A3 b D D2 e E E2 L L E E2 Top View Bottom View b D2 MILLIMETERS MIN MAX 0.80 1.00 0 0.05 0.20 REF 0.18 0.30 3.00 BSC 2.23 2.48 0.50 BSC 3.00 BSC 1.49 1.74 0.30 0.50 INCHES MIN MAX 0.0315 0.0394 0 0.0019 0.0079 REF 0.0071 0.0118 0.1181 BSC 0.0878 0.0976 0.0197 BSC 0.1181 BSC 0.0587 0.0685 0.0071 0.0197 Note: A A3 A1 1. Dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(.006”) on any side. Lead dimension shall not include solder coverage. LX13088 PRODUCTION DATA – Information contained in this document is proprietary to Microsemi and is current as of publication date. This document may not be modified in any way without the express written consent of Microsemi. Product processing does not necessarily include testing of all parameters. Microsemi reserves the right to change the configuration and performance of the product and to discontinue product at any time. Copyright © 2010 Rev. 1.1, 2010-06-08 Microsemi Analog Mixed Signal Group 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 12