LM2840XMKX-ADJL

LM2840 TI1 | Alldatasheet

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Technical content

Features

■ LM2840Q, LM2841Q and LM2842Q are Automotive Grade products that are AEC-Q100 grade 1 qualified (-40° C to +125°C operating junction temperature) ■ Input voltage range of 4.5V to 42V ■ Output current options of 100 mA, 300 mA and 600 mA ■ Feedback pin voltage of 0.765V ■ 550 kHz (X) or 1.25 MHz (Y) switching frequency ■ Low shutdown IQ, 16 µA typical ■ Short circuit protected ■ Internally compensated ■ Soft-start circuitry ■ Small overall solution size (TSOT-6L package)

Applications

■ Battery powered equipment ■ Industrial distributed power applications ■ Portable media players ■ Portable hand held instruments Typical Application Circuit 30036702 © 2012 Texas Instruments Incorporated 300367 SNVS540G www.ti.com LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q 100/300/600 mA 42V Input Step-Down DC/DC Regulator in Thin SOT-23

Ordering Information

Order Number Spec. Package Type NSC Package Drawing Top Mark Supplied As Feature LM2840XMK-ADJL NOPB TSOT-6 MK06A SE8B 1000 Units, Tape and Reel LM2840XMKX-ADJL 3000 Units, Tape and Reel LM2840YMK-ADJL SF1B 1000 Units, Tape and Reel LM2840YMKX-ADJL 3000 Units, Tape and Reel LM2841XMK-ADJL STFB 1000 Units, Tape and Reel LM2841XMKX-ADJL 3000 Units, Tape and Reel LM2841YMK-ADJL STTB 1000 Units, Tape and Reel LM2841YMKX-ADJL 3000 Units, Tape and Reel LM2842XMK-ADJL STVB 1000 Units, Tape and Reel LM2842XMKX-ADJL 3000 Units, Tape and Reel LM2842YMK-ADJL STXB 1000 Units, Tape and Reel LM2842YMKX-ADJL 3000 Units, Tape and Reel LM2840XQMK SE9B 1000 Units, Tape and Reel AEC-Q100 Grade 1 qualified. Automotive Grade Production Flow* LM2840XQMKX 3000 Units, Tape and Reel LM2840YQMK SF2B 1000 Units, Tape and Reel LM2840YQMKX 3000 Units, Tape and Reel LM2841XQMK SB1B 1000 Units, Tape and Reel LM2841XQMKX 3000 Units, Tape and Reel LM2841YQMK SB2B 1000 Units, Tape and Reel LM2841YQMKX 3000 Units, Tape and Reel LM2842XQMK SB3B 1000 Units, Tape and Reel LM2842XQMKX 3000 Units, Tape and Reel LM2842YQMK SB4B 1000 Units, Tape and Reel LM2842YQMKX 3000 Units, Tape and Reel *Automotive Grade (Q) product incorporates enhanced manufacturing and support processes for the automotive market, including defect detection methodologies. Reliability qualification is compliant with the requirements and temperature grades defined in the AEC-Q100 standard. Automotive grade products are identified with the letter Q. For more information go to http://www.national.com/automotive. www.ti.com 2 LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q

1 CB SW FET gate bias voltage. Connect CBOOT cap between CB and SW. 2 GND Ground connection. 3 FB Feedback pin: Set feedback voltage divider ratio with VOUT = VFB (1+(R1/R2)). Resistors should be in the 100-10K range to avoid input bias errors. 4 SHDN Logic level shutdown input. Pull to GND to disable the device and pull high to enable the device. If this function is not used tie to VIN or leave open. 5 VIN Power input voltage pin: 4.5V to 42V normal operating range. 6 SW Power FET output: Connect to inductor, diode, and CBOOT cap. 3 www.ti.com LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q

Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. VIN -0.3V to +45V SHDN -0.3V to (VIN+0.3V) <45V SW Voltage -0.3V to +45V CB Voltage above SW Voltage 7V FB Voltage -0.3V to +5V Maximum Junction Temperature 150°C Power Dissipation(Note 2) Internally Limited Lead Temperature 300°C Vapor Phase (60 sec.) 215°C Infrared (15 sec.) 220°C ESD Susceptibility (Note 3) Human Body Model 2 kV Operating Conditions Operating Junction Temperature Range (Note 4) −40°C to +125°C Storage Temperature −65°C to +150°C Input Voltage VIN 4.5V to 42V SW Voltage Up to 42V

Electrical Characteristics

Specifications in standard type face are for TJ = 25°C and those with boldface type apply over the full Operating Temperature Range ( TJ = −40°C to +125°C). Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = +25°C, and are provided for reference purposes only. Unless otherwise stated the following conditions apply: VIN = 12V. Symbol Parameter Conditions Min (Note 4) Typ (Note 5) Max (Note 4) Units IQ Quiescent current SHDN = 0V 16 40 µA Device On, Not Switching 1.30 1.75 mADevice On, No Load 1.35 1.85 RDSON Switch ON resistance (Note 6) 0.9 1.6 Ω ILSW Switch leakage current VIN = 42V 0.0 0.5 µA ICL Switch current limit LM2840 (Note 7) 525 900 mA LM2841 (Note 7) 525 900 mA LM2842 (Note 7) 1.15 1.7 A IFB Feedback pin bias current LM2840/41/42 (Note 8) 0.1 1.0 µA VFB FB Pin reference voltage 0.747 0.765 0.782 V tON(min) Minimum ON time (Note 10) 100 150 ns tOFF(min) Minimum OFF time X option 110 370 ns Y option 104 200 ns fSW Switching frequency LM2840/41/42X, VFB = 0.5V 325 550 750 kHzLM2840/41/42X, VFB = 0V 140 LM2840/41/42Y, VFB = 0.5V 0.95 1.25 1.50 MHzLM2840/41/42Y, VFB = 0V 0.35 DMAX Maximum duty cycle LM2840/41/42X 88 94 LM2840/41/42Y 81 87 VUVP Undervoltage lockout thresholds On threshold 4.4 3.7 VOff threshold 3.5 3.25 VSHDN Shutdown threshold Device on 2.3 1.0 VDevice off 0.9 0.3 ISHDN Shutdown pin input bias current VSHDN = 2.3V (Note 8) 0.05 1.5 µAVSHDN = 0V 0.02 1.5 THERMAL SPECIFICATIONS RθJA Junction-to-Ambient Thermal Resistance, TSOT-6L Package (Note 9) 121 °C/W RθJC Junction-to-Case Thermal Resistance, TSOT-6L Package 94 °C/W www.ti.com 4 LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q

Note 1: Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended to be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PD (MAX) = (TJ(MAX) − TA)/ θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=175°C (typ.) and disengages at TJ= 155°C (typ). Note 3: Human Body Model, applicable std. JESD22-A114-C. Note 4: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are 100% production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Note 5: Typical numbers are at 25°C and represent the most likely norm. Note 6: Includes the bond wires, RDSON from VIN pin to SW pin. Note 7: Current limit at 0% duty cycle. May be lower at higher duty cycle or input voltages below 6V. Note 8: Bias currents flow into pin. Note 9: All numbers apply for packages soldered directly onto a 3" x 3" PC board with 2 oz. copper on 4 layers in still air in accordance to JEDEC standards. Thermal resistance varies greatly with layout, copper thickness, number of layers in PCB, power distribution, number of thermal vias, board size, ambient temperature, and air flow. Note 10: Minimum On Time guaranteed by design and simulation. 5 www.ti.com LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q

Typical Performance Characteristics Efficiency vs. Load Current (LM2842X, VOUT = 3.3V) 30036718 Efficiency vs. Load Current (LM2841X, VOUT = 3.3V) 30036719 Efficiency vs. Load Current (LM2840X, VOUT = 8V) 30036720 Switching Frequency vs. Temperature (X version) 30036766 Input UVLO Voltage vs. Temperature 30036767 Switch Current Limit vs. SHDN Pin Voltage (Soft-start Implementation, LM2840/41) 30036768 www.ti.com 6 LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q

Switch Current Limit vs. SHDN Pin Voltage (Soft-start Implementation, LM2842) 30036721 SHDN Pin Current vs. SHDN Pin Voltage 30036769 Switching Node and Output Voltage Waveforms 30036770 VIN = 12V, VOUT = 3.3V, IOUT = 200 mA Top trace: VOUT, 10 mV/div, AC Coupled Bottom trace: SW, 5V/div, DC Coupled T = 1 µs/div Load Transient Waveforms 30036771 VIN = 12V, VOUT = 3.3V, IOUT = 300 mA to 200 mA to 300 mA Top trace: VOUT, 20 mV/div, AC Coupled Bottom trace: IOUT, 100 mA/div, DC Coupled T = 200 µs/div Start-up Waveform 30036772 VIN = 12V, VOUT = 3.3V, IOUT = 50 mA Top trace: VOUT, 1V/div, DC Coupled Bottom trace: SHDN, 2V/div, DC Coupled T = 40 µs/div 7 www.ti.com LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q

The LM2840/1/2 has dedicated protection circuitry running during normal operation to protect the IC. The thermal shut- down circuitry turns off the power device when the die tem- perature reaches excessive levels. The UVLO comparator protects the power device during supply power startup and shutdown to prevent operation at voltages less than the min- imum input voltage. A gate drive (CB) under-voltage lockout is included to guarantee that there is enough gate drive volt- age to drive the MOSFET before the device tries to start switching. The LM2840/1/2 also features a shutdown mode decreasing the supply current to approximately 16 µA. CONTINUOUS CONDUCTION MODE The LM2840/1/2 contains a current-mode, PWM buck regu- lator. A buck regulator steps the input voltage down to a lower output voltage. In continuous conduction mode (when the in- ductor current never reaches zero at steady state), the buck regulator operates in two cycles. The power switch is con- nected between VIN and SW. In the first cycle of operation the transistor is closed and the diode is reverse biased. Energy is collected in the inductor and the load current is supplied by COUT and the rising current through the inductor. During the second cycle the transistor is open and the diode is forward biased due to the fact that the inductor current cannot instan- taneously change direction. The energy stored in the inductor is transferred to the load and output capacitor. The ratio of these two cycles determines the output voltage. The output voltage is defined approximately as: D=VOUT/VIN and D’ = (1- D) where D is the duty cycle of the switch. D and D' will be required for design calculations. DESIGN PROCEDURE This section presents guidelines for selecting external com- ponents. SETTING THE OUTPUT VOLTAGE The output voltage is set using the feedback pin and a resistor divider connected to the output as shown on the front page schematic. The feedback pin voltage 0.765V, so the ratio of the feedback resistors sets the output voltage according to the following equation: V OUT=0.765V(1+(R1/R2)) Typically R2 will be given as 100Ω-10 kΩ for a starting value. To solve for R1 given R2 and VOUT use R1=R2((VOUT/0.765V)-1). INPUT CAPACITOR A low ESR ceramic capacitor (C IN) is needed between the VIN pin and GND pin. This capacitor prevents large voltage transients from appearing at the input. Use a 2.2 µF-10 µF value with X5R or X7R dielectric. Depending on construction, a ceramic capacitor’s value can decrease up to 50% of its nominal value when rated voltage is applied. Consult with the capacitor manufacturer's data sheet for information on ca- pacitor derating over voltage and temperature. www.ti.com 8 LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q

The most critical parameters for the inductor are the induc- tance, peak current, and the DC resistance. The inductance is related to the peak-to-peak inductor ripple current, the input and the output voltages. A higher value of ripple current reduces inductance, but in- creases the conductance loss, core loss, and current stress for the inductor and switch devices. It also requires a bigger output capacitor for the same output voltage ripple require- ment. A reasonable value is setting the ripple current to be 30% of the DC output current. Since the ripple current in- creases with the input voltage, the maximum input voltage is always used to determine the inductance. The DC resistance of the inductor is a key parameter for the efficiency. Lower DC resistance is available with a bigger winding area. A good tradeoff between the efficiency and the core size is letting the inductor copper loss equal 2% of the output power. See AN-1197 for more information on selecting inductors. A good starting point for most applications is a 10 µH to 22 µH with 1.1A or greater current rating for the LM2842 or a 0.7A or greater current rating for the LM2840/41. Using such a rating will enable the LM2840/1/2 to current limit without saturating the inductor. This is preferable to the LM2840/1/2 going into thermal shutdown mode and the possibility of damaging the inductor if the output is shorted to ground or other longterm overload. OUTPUT CAPACITOR The selection of C OUT is driven by the maximum allowable output voltage ripple. The output ripple in the constant fre- quency, PWM mode is approximated by: V RIPPLE = I RIPPLE (ESR+(1/(8fSWCOUT))) The ESR term usually plays the dom- inant role in determining the voltage ripple. Low ESR ceramic capacitors are recommended. Capacitors in the range of 22 µF-100 µF are a good starting point with an ESR of 0.1 Ω or less. BOOTSTRAP CAPACITOR A 0.15 µF ceramic capacitor or larger is recommended for the bootstrap capacitor (CBOOT). For applications where the input voltage is less than twice the output voltage a larger capacitor is recommended, generally 0.15 µF to 1 µF to ensure plenty of gate drive for the internal switches and a consistently low RDSON. SOFT-START COMPONENTS The LM2840/1/2 has circuitry that is used in conjunction with the SHDN pin to limit the inrush current on start-up of the DC/ DC switching regulator. The SHDN pin in conjunction with a RC filter is used to tailor the soft-start for a specific application. When a voltage applied to the SHDN pin is between 0V and up to 2.3V it will cause the cycle by cycle current limit in the power stage to be modulated for minimum current limit at 0V up to the rated current limit at 2.3V. Thus controlling the output rise time and inrush current at startup. The resistor value should be selected so the current sourced into the SHDN pin will be greater then the leakage current of the SHDN pin (1.5 µA ) when the voltage at SHDN is equal or greater then 2.3V. SHUTDOWN OPERATION The SHDN pin of the LM2840/1/2 is designed so that it may be controlled using 2.3V or higher logic signals. If the shut- down function is not to be used the SHDN pin may be tied to VIN. The maximum voltage to the SHDN pin should not ex- ceed 42V. If the use of a higher voltage is desired due to system or other constraints it may be used, however a 100 kΩ or larger resistor is recommended between the applied voltage and the SHDN pin to protect the device. SCHOTTKY DIODE The breakdown voltage rating of the diode (D1) is preferred to be 25% higher than the maximum input voltage. The cur- rent rating for the diode should be equal to the maximum output current for best reliability in most applications. In cases where the duty cycle is greater than 50%, the average diode current is lower. In this case it is possible to use a diode with a lower average current rating, approximately (1-D)IOUT, how- ever the peak current rating should be higher than the maxi- mum load current. A 0.5A to 1A rated diode is a good starting point. LAYOUT CONSIDERATIONS To reduce problems with conducted noise pick up, the ground side of the feedback network should be connected directly to the GND pin with its own connection. The feedback network, resistors R1 and R2, should be kept close to the FB pin, and away from the inductor to minimize coupling noise into the feedback pin. The input bypass capacitor CIN must be placed close to the VIN pin. This will reduce copper trace resistance which effects input voltage ripple of the IC. The inductor L1 should be placed close to the SW pin to reduce EMI and ca- pacitive coupling. The output capacitor, C OUT should be placed close to the junction of L1 and the diode D1. The L1, D1, and COUT trace should be as short as possible to reduce conducted and radiated noise and increase overall efficiency. The ground connection for the diode, C IN, and COUT should be as small as possible and tied to the system ground plane in only one spot (preferably at the COUT ground point) to min- imize conducted noise in the system ground plane. For more detail on switching power supply layout considerations see Application Note AN-1149: Layout Guidelines for Switching Power Supplies. 9 www.ti.com LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q

Physical Dimensions inches (millimeters) unless otherwise noted TSOT 6 Pin Package (MK) For Ordering, Refer to Ordering Information Table www.ti.com 12 LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q

13 www.ti.com LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q

LM2840/LM2841/LM2842/LM2840Q/LM2841Q/LM2842Q 100/300/600 mA 42V Input Step-Down DC/DC Regulator in Thin SOT-23 www.ti.com

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