LM2704MFX-ADJ

LM2704 www.ti.com SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 LM2704 Micropower Step-up DC/DC Converter with 550mA Peak Current Limit Check for Samples: LM2704 FEATURES DESCRIPTION • • • • • • • The LM2704 is a micropower step-up DC/DC in a small 5-lead SOT-23 package. A current limited, fixed off-time control scheme conserves operating current resulting in high efficiency over a wide range of load conditions. The 21V switch allows for output voltages as high as 20V. The low 400ns off-time permits the use of tiny, low profile inductors and capacitors to minimize footprint and cost in space-conscious portable applications. The LM2704 is ideal for LCD panels requiring low current and high efficiency as well as white LED applications for cellular phone back-lighting. The LM2704 can drive up to 8 white LEDs from a single Li-Ion battery. 1 2 550mA, 0.7Ω, Internal Switch Uses Small Surface Mount Components Adjustable Output Voltage up to 20V 2.2V to 7V Input Range Input Undervoltage Lockout 0.01µA Shutdown Current Small 5-Lead SOT-23 Package APPLICATIONS • • • • • LCD Bias Supplies White LED Back-Lighting Handheld Devices Digital Cameras Portable Applications Typical Application Circuit 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2002–2013, Texas Instruments Incorporated LM2704 SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 www.ti.com Connection Diagram The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junctionto-ambient thermal resistance, θJA, and the ambient temperature, TA. See the Electrical Characteristics table for the thermal resistance. 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. Figure 1. SOT23-5 - Top View TJmax = 125°C, θJA = 220°C/W PIN DESCRIPTIONS Pin Name Function 1 SW Power Switch input. 2 GND Ground. 3 FB 4 SHDN 5 VIN Output voltage feedback input. Shutdown control input, active low. Analog and Power input. SW(Pin 1): Switch Pin. This is the drain of the internal NMOS power switch. Minimize the metal trace area connected to this pin to minimize EMI. GND(Pin 2): Ground Pin. Tie directly to ground plane. FB(Pin 3): Feedback Pin. Set the output voltage by selecting values for R1 and R2 using: (1) Connect the ground of the feedback network to an AGND plane which should be tied directly to the GND pin. SHDN(Pin 4): Shutdown Pin. The shutdown pin is an active low control. Tie this pin above 1.1V to enable the device. Tie this pin below 0.3V to turn off the device. VIN(Pin 5): Input Supply Pin. Bypass this pin with a capacitor as close to the device as possible. These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 2 Submit Documentation Feedback Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 LM2704 www.ti.com SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 Absolute Maximum Ratings (1) (2) VIN 7.5V SW Voltage 21V FB Voltage 2V SHDN Voltage 7.5V Maximum Junction Temp. TJ (3) 150°C Lead Temperature (Soldering 10 sec.) 300°C Vapor Phase (60 sec.) 215°C Infrared (15 sec.) 220°C (4) ESD Ratings Human Body Model Machine Model (5) (1) 2kV 200V 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 ensured. For ensured specifications and test conditions, see the Electrical Characteristics. If Military/Aerospace specified devices are required, please contact the TI Sales Office/Distributors for availability and specifications. 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. See the Electrical Characteristics table for the thermal resistance. 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. The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged directly into each pin. ESD susceptibility using the machine model is 150V for SW pin. (2) (3) (4) (5) Operating Conditions Junction Temperature (1) −40°C to +125°C Supply Voltage 2.2V to 7V SW Voltage Max. (1) 20.5V All limits ensured at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are 100% production tested or ensured through statistical analysis. All limits at temperature extremes are ensured via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Electrical Characteristics (1) Specifications in standard type face are for TJ = 25°C and those in boldface type apply over the full Operating Temperature Range (TJ = −40°C to +125°C). Unless otherwise specified. VIN =2.2V. Symbol IQ Parameter Min Conditions (1) Typ Max 40 70 (2) (1) Device Disabled FB = 1.3V Device Enabled FB = 1.2V 235 300 Shutdown SHDN = 0V 0.01 2.5 Units µA VFB Feedback Trip Point 1.189 1.237 1.269 V ICL Switch Current Limit 490 420 550 610 620 mA 30 120 nA 7.0 V IB FB Pin Bias Current VIN Input Voltage Range RDSON Switch RDSON 0.7 TOFF Switch Off Time 400 (1) (2) (3) FB = 1.23V (3) 2.2 1.6 Ω ns All limits ensured at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are 100% production tested or ensured through statistical analysis. All limits at temperature extremes are ensured via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25°C and represent the most likely norm. Feedback current flows into the pin. Submit Documentation Feedback Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 3 LM2704 SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 www.ti.com Electrical Characteristics(1) (continued) Specifications in standard type face are for TJ = 25°C and those in boldface type apply over the full Operating Temperature Range (TJ = −40°C to +125°C). Unless otherwise specified. VIN =2.2V. Symbol ISD Parameter SHDN Pin Current Typ Max SHDN = VIN, TJ = 25°C 0 80 SHDN = VIN, TJ = 125°C 15 SHDN = GND 0 Conditions Min (1) (2) IL Switch Leakage Current VSW = 20V 0.05 UVP Input Undervoltage Lockout ON/OFF Threshold 1.8 VFB Hysteresis Feedback Hysteresis SHDN Threshold SHDN low θJA Thermal Resistance 4 (1) nA 5 0.7 1.1 0.7 220 Submit Documentation Feedback µA V 8 SHDN High Units mV 0.3 V °C/W Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 LM2704 www.ti.com SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 Typical Performance Characteristics Enable Current vs VIN (Part Switching) Disable Current vs VIN (Part Not Switching) Efficiency vs Load Current Efficiency vs Load Current Efficiency vs Load Current SHDN Threshold vs VIN Submit Documentation Feedback Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 5 LM2704 SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) 6 Switch Current Limit vs VIN Switch RDSON vs VIN FB Trip Point and FB Pin Current vs Temperature Output Voltage vs Load Current Submit Documentation Feedback Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 LM2704 www.ti.com SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 Typical Performance Characteristics (continued) Step Response VOUT = 20V, VIN = 3.0V 1) Load, 1mA to 17mA to 1mA, DC 2) VOUT, 200mV/div, AC 3) IL, 500mA/div, DC T = 40µs/div Start-Up/Shutdown VOUT = 20V, VIN = 2.5V 1) SHDN, 1V/div, DC 2) IL, 250mA/div, DC 3) VOUT, 20V/div, DC T = 400µs/div RL = 1.3kΩ Submit Documentation Feedback Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 7 LM2704 SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 www.ti.com OPERATION Figure 2. LM2704 Block Diagram VOUT = 20V, VIN = 2.5V 1) VSW, 20V/div, DC 2) Inductor Current, 500mA/div, DC 3) VOUT, 100mV/div, AC T = 10µs/div Figure 3. Typical Switching Waveform The LM2704 features a constant off-time control scheme. Operation can be best understood by referring to Figure 2 and Figure 3. Transistors Q1 and Q2 and resistors R3 and R4 of Figure 2 form a bandgap reference used to control the output voltage. When the voltage at the FB pin is less than 1.237V, the Enable Comp in Figure 2 enables the device and the NMOS switch is turned on pulling the SW pin to ground. When the NMOS switch is on, current begins to flow through inductor L while the load current is supplied by the output capacitor COUT. Once the current in the inductor reaches the peak current limit, the CL Comp trips and the 400ns One Shot 8 Submit Documentation Feedback Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 LM2704 www.ti.com SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 turns off the NMOS switch. The SW voltage will then rise to the output voltage plus a diode drop and the inductor current will begin to decrease as shown in Figure 3. During this time the energy stored in the inductor is transferred to COUT and the load. After the 400ns off-time the NMOS switch is turned on and energy is stored in the inductor again. This energy transfer from the inductor to the output causes a stepping effect in the output ripple as shown in Figure 3. This cycle is continued until the voltage at FB reaches 1.237V. When FB reaches this voltage, the enable comparator then disables the device turning off the NMOS switch and reducing the Iq of the device to 40uA. The load current is then supplied solely by COUT indicated by the gradually decreasing slope at the output as shown in Figure 3. When the FB pin drops slightly below 1.237V, the enable comparator enables the device and begins the cycle described previously. The SHDN pin can be used to turn off the LM2704 and reduce the Iq to 0.01µA. In shutdown mode the output voltage will be a diode drop lower than the input voltage. APPLICATION INFORMATION INDUCTOR SELECTION The appropriate inductor for a given application is calculated using the following equation: (2) where VD is the schottky diode voltage, ICL is the switch current limit found in the Typical Performance Characteristics section, and TOFF is the switch off time. When using this equation be sure to use the minimum input voltage for the application, such as for battery powered applications. For the LM2704 constant-off time control scheme, the NMOS power switch is turned off when the current limit is reached. There is approximately a 200ns delay from the time the current limit is reached in the NMOS power switch and when the internal logic actually turns off the switch. During this 200ns delay, the peak inductor current will increase. This increase in inductor current demands a larger saturation current rating for the inductor. This saturation current can be approximated by the following equation: (3) Choosing inductors with low ESR decrease power losses and increase efficiency. Care should be taken when choosing an inductor. For applications that require an input voltage that approaches the output voltage, such as when converting a Li-Ion battery voltage to 5V, the 400ns off time may not be enough time to discharge the energy in the inductor and transfer the energy to the output capacitor and load. This can cause a ramping effect in the inductor current waveform and an increased ripple on the output voltage. Using a smaller inductor will cause the IPK to increase and will increase the output voltage ripple further. This can be solved by adding a 4.7pF capacitor across the RF1 feedback resistor (Figure 2) and slightly increasing the output capacitor. A smaller inductor can then be used to ensure proper discharge in the 400ns off time. DIODE SELECTION To maintain high efficiency, the average current rating of the schottky diode should be larger than the peak inductor current, IPK. Schottky diodes with a low forward drop and fast switching speeds are ideal for increasing efficiency in portable applications. Choose a reverse breakdown of the schottky diode larger than the output voltage. CAPACITOR SELECTION Choose low ESR capacitors for the output to minimize output voltage ripple. Multilayer ceramic capacitors are the best choice. For most applications, a 1µF ceramic capacitor is sufficient. For some applications a reduction in output voltage ripple can be achieved by increasing the output capacitor. Local bypassing for the input is needed on the LM2704. Multilayer ceramic capacitors are a good choice for this as well. A 4.7µF capacitor is sufficient for most applications. For additional bypassing, a 100nF ceramic capacitor can be used to shunt high frequency ripple on the input. Submit Documentation Feedback Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 9 LM2704 SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 www.ti.com LAYOUT CONSIDERATIONS The input bypass capacitor CIN, as shown in Typical Application Circuit, must be placed close to the IC. This will reduce copper trace resistance which effects input voltage ripple of the IC. For additional input voltage filtering, a 100nF bypass capacitor can be placed in parallel with CIN to shunt any high frequency noise to ground. The output capacitor, COUT, should also be placed close to the IC. Any copper trace connections for the Cout capacitor can increase the series resistance, which directly effects output voltage ripple. The feedback network, resistors R1 and R2, should be kept close to the FB pin to minimize copper trace connections that can inject noise into the system. The ground connection for the feedback resistor network should connect directly to an analog ground plane. The analog ground plane should tie directly to the GND pin. If no analog ground plane is available, the ground connection for the feedback network should tie directly to the GND pin. Trace connections made to the inductor and schottky diode should be minimized to reduce power dissipation and increase overall efficiency. Figure 4. White LED Application Figure 5. Li-Ion 5V Application Figure 6. Li-Ion 12V Application 10 Submit Documentation Feedback Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 LM2704 www.ti.com SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 Figure 7. 5V to 12V Application Submit Documentation Feedback Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 11 LM2704 SNVS175D – FEBRUARY 2002 – REVISED MAY 2013 www.ti.com REVISION HISTORY Changes from Revision C (May 2013) to Revision D • 12 Page Changed layout of National Data Sheet to TI format .......................................................................................................... 11 Submit Documentation Feedback Copyright © 2002–2013, Texas Instruments Incorporated Product Folder Links: LM2704 PACKAGE OPTION ADDENDUM www.ti.com 10-Dec-2020 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) LM2704MF-ADJ/NOPB ACTIVE SOT-23 DBV 5 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 85 S28B (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of