LM2751 www.ti.com SNVS299B – APRIL 2005 – REVISED MAY 2013 LM2751 Regulated 2X, 1.5X Switched Capacitor White LED Driver Check for Samples: LM2751 FEATURES APPLICATIONS • • • • • • • 1 2 • • • • • • Regulated Output Options: 4.5V, 5.0V Output Voltage Regulated Within 3% Peak Efficiency Over 90% 150mA (4.5V) or 80mA (5.0V) Output Current Capability Input Voltage Range: 2.8V to 5.5V Low Input and Output Voltage Ripple <1µA Typical Shutdown Current Small Solution Size - NO INDUCTOR Programmable 725kHz, 300kHz, 37kHz, or 9.5kHz Switching Frequencies 10-pin SON No-Pullback Package: 3mm × 3mm × 0.8mm White LED Display Backlights White LED Keypad Backlights General Purpose 2×, 1.5× Regulated Charge Pump DESCRIPTION The LM2751 is a constant frequency switched capacitor charge pump with regulated output voltage options of 4.5V, and 5.0V. Over the input voltage range of 2.8V to 5.5V the LM2751 provides up to 150mA of output current and requires only four lowcost ceramic capacitors. Typical Application Circuit VOUT = 4.5V, or 5.0V VIN = 2.8V - 5.5V 3 CIN 2 2.2 µF C1 VIN VOUT 1 C1+ 2.2 µF 9 10 C 1C 2+ LM2751 EN CS1 Capacitors: C 2- DX R R 4 1 µF 7 D1 6 CS0 C2 COUT 1 µF 5 GND 8 1 µF - TDK C1608X7R1A105K 2.2 µF - TDK C2012X5R1A225K LM2751 2x/1.5x Efficiency vs. 2x Charge Pump Efficiency 100 EFFICIENCY (%) 90 LM2751 2x, 1.5x Pump VOUT = 4.5V VOUT = 5.0V 80 70 60 VOUT = 5.0V VOUT = 4.5V 50 Typical 2x Only Pump 40 2.7 3.0 3.3 3.6 3.9 4.2 INPUT VOLTAGE (V) 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 © 2005–2013, Texas Instruments Incorporated LM2751 SNVS299B – APRIL 2005 – REVISED MAY 2013 www.ti.com DESCRIPTION (CONTINUED) The LM2751 provides excellent efficiency without the use of an inductor by operating the charge pump in a gain of 3/2 or 2. The proper gain for maintaining regulation is chosen so that efficiency is maximized over the input voltage range. LM2751 uses constant frequency pre-regulation to minimize conducted noise on the input and provide a predictable switching frequency. The switching frequency is programmable to 725kHz, 300kHz, 37kHz, or 9.5kHz. LM2751 is available in a 10-pin SON No-Pullback Package. Connection Diagram VOUT 1 10 C2+ C2+ 10 1 VOUT C1+ 2 9 C1- C1- 9 2 C1+ VIN 3 8 GND GND 8 3 VIN CS0 4 7 C2- C2- 7 4 CS0 CS1 5 6 EN EN 6 5 CS1 Die-Attach Pad: GND Die-Attach Pad: GND Top View Bottom View Figure 1. 10-pin SON No Pullback Package (3mm × 3mm × 0.8mm) See Package Number DSC0010A PIN DESCRIPTIONS Pin # Name Description 1 VOUT 2 C1+ Flying Capacitor C1 Connection. 3 VIN Input Supply Range: 2.8V to 5.5V. 4 CS0 Frequency Select Input 0. 5 CS1 Frequency Select Input 1. 6 EN Enable Pin Logic Input. 7 C2− Flying Capacitor C2 Connection. 8 GND 9 C1− Flying Capacitor C1 Connection. 10 C2+ Flying Capacitor C2 Connection. Pre-Regulated Output. Ground. 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 © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 LM2751 www.ti.com SNVS299B – APRIL 2005 – REVISED MAY 2013 ABSOLUTE MAXIMUM RATINGS (1) (2) (3) −0.3V to 6.0V VIN Pin −0.3V to (VIN+0.3) w/ 6.0V max EN, CS0, CS1 Pins Continuous Power Dissipation (4) Internally Limited Junction Temperature (TJ-MAX-ABS) 150°C −65°C to 150°C Storage Temperature Range Maximum Lead Temperature ESD Rating (5) (Soldering, 10sec.) 265°C Human-body model 2kV Machine model (1) (2) (3) (4) (5) 200V Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of the device is specified. Operating Ratings do not imply ensured performance limits. For specified performance limits and associated test conditions, see the Electrical Characteristics tables. All voltages are with respect to the potential at the GND pin. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=150°C (typ.) and disengages at TJ=140°C (typ.). The Human body model is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin. The machine model is a 200pF capacitor discharged directly into each pin (MIL-STD-883 3015.7). OPERATING RATINGS (1) (2) Input Voltage Range 2.8V to 5.5V EN, CS0, CS1 Input Voltage Range 0V to VIN Junction Temperature (TJ) Range -40°C to 115°C Ambient Temperature (TA) Range (3) -40°C to 85°C Recommended Maximum Load Current Version B Version A (1) (2) (3) Freq. = 725kHz 150mA Freq. = 300kHz 120mA Freq. = 37kHz 40mA Freq. = 9.5kHz 10mA Freq. = 725kHz 80mA Freq. = 300kHz 60mA Freq. = 37kHz 16mA Freq. = 9.5kHz 4mA Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of the device is specified. Operating Ratings do not imply ensured performance limits. For specified performance limits and associated test conditions, see the Electrical Characteristics tables. All voltages are with respect to the potential at the GND pin. In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operation junction temperature (TJ-MAX-OP = 115ºC), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the part/package in the application (θJA), as given by the following equation: TA-MAX = TJ-MAX-OP - (θJA × PD-MAX). THERMAL PROPERTIES Junction-to-Ambient Thermal Resistance, 10-pin SON (1) Package (θJA) (1) 55°C/W Junction-to-ambient thermal resistance (θJA) is taken from a thermal modeling result, performed under the conditions and guidelines set forth in the JEDEC standard JESD51-7. The test board is a 4 layer FR-4 board measuring 102mm x 76mm x 1.6mm with a 2 x 1 array of thermal vias. The ground plane on the board is 50mm x 50mm. Thickness of copper layers are 36µm/18µm /18µm/36µm(1.5oz/1oz/1oz/1.5oz). Ambient temperature in simulation is 22ºC, still air. Power dissipation is 1W. The value of θJA of the LM2751 in 10-pin SON could fall in a range as wide as 50ºC/W to 150ºC/W (if not wider), depending on PWB material, layout, and environmental conditions. In applications where high maximum power dissipation exists (high VIN, high IOUT), special care must be paid to thermal dissipation issues. For more information on these topics, see the TI AN-1187 Application Report (SNOA401) and the Power Efficiency and Power Dissipation section of this datasheet. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 3 LM2751 SNVS299B – APRIL 2005 – REVISED MAY 2013 www.ti.com ELECTRICAL CHARACTERISTICS (1) (2) Limits in standard typeface are for TA = 25ºC. Limits in boldface type apply over the full operating ambient temperature range (-40°C ≤ TA ≤ +85°C) . Unless otherwise noted, specifications apply to the LM2751 Typical Application Circuit (pg. 1) with: VIN = 3.6V, V(EN) = VIN, CS0 = CS1 = VIN, C1 = C2 = 1.0µF, CIN = COUT = 2.2µF (3). Symbol VOUT Parameter Output Voltage Conditions Version A, 2.8V ≤ VIN ≤ 5.5V, Freq. = 300kHz, 725kHz, TA = 25°C IOUT = 0 to 60mA Min Typ Max Units 4.850 (-3%) 5.0 5.150 (+3%) V Version A, 2.8V ≤ VIN ≤ 5.5V, Freq. = 300kHz, IOUT = 0 to 60mA Freq. = 725kHz, IOUT = 0 to 80mA 4.775 (-4.5%) Version B, 2.8V ≤ VIN ≤ 5.5V, Freq. = 300kHz, 725kHz, TA = 25°C IOUT = 0 to 120mA 4.343 (-3.5%) Version B, 2.8V ≤ VIN ≤ 5.5V, Freq. = 300kHz, IOUT = 0 to 120mA Freq. = 725kHz, IOUT = 0 to 150mA 4.275 (-5%) 5.225 (+4.5%) 4.5 4.658 (+3.5%) 4.725 (+5%) VR Output Ripple 2.8V ≤ VIN ≤ 5.5V IOUT = 60mA IQ Quiescent Current Freq. = 9.5kHz, IOUT = 0mA, VIN = 3.7V 425 600 Freq. = 37kHz, IOUT = 0mA, VIN = 3.7V 450 640 ISD E f SW Shutdown Supply Current Efficiency Switching Frequency 8 mV Freq. = 300kHz, IOUT = 0mA, VIN = 3.7V 700 900 Freq. = 725kHz, IOUT = 0mA, VIN = 3.7V 1000 1500 V(EN) = 0V 0.77 1.3 V(EN) = 0V, TA = 85°C 1.0 IOUT = 80mA (Version A, 5.0V) Freq. = 300kHz, 725kHz 92 IOUT = 150mA (Version B, 4.5V) Freq. = 300kHz, 725kHz 83 µA µA % CS0 = High, CS1 = Low 2.8V ≤ VIN ≤ 5.5V 6.7 (−30%) 9.5 12.3 (+30%) CS0 = Low, CS1 = Low 2.8V ≤ VIN ≤ 5.5V 26 (−30%) 37 48 (+30%) CS0 = Low, CS1 = High 2.8V ≤ VIN ≤ 5.5V 210 (−30%) 300 390 (+30%) CS0 = High, CS1 = High 2.8V ≤ VIN ≤ 5.5V 508 (−30%) 725 942 (+30%) kHz VIH Logic Input High Input Pins: EN, CS0, CS1 2.8V ≤ VIN ≤ 5.5V 1.00 VIN V VIL Logic Input Low Input Pins: EN, CS0, CS1 2.8V ≤ VIN ≤ 5.5V 0 .30 V IIH Logic Input High Current Input Pins: CS0, CS1 V(CSx) = 1.8V 10 nA Input Pin: EN V(EN) = 1.8V (4) 2 µA 10 nA 3.50 3.58 V IIL Logic Input Low Current Input Pins: EN, CS0, CS1 V(EN, CSx) = 0V VG Gain Transition Voltage (Version A, B) 1.5X to 2X 2X to 1.5X ISC Short Circuit Output Current Hysteresis (1) (2) (3) (4) 4 40 VOUT = 0V 80 250 150 mV mA All voltages are with respect to the potential at the GND pin. Min and Max limits are specified by design, test, or statistical analysis. Typical numbers are not ensured, but represent the most likely norm. CIN, COUT, C1, and C2: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics. EN Logic Input High Current (IIH) is due to a 1MΩ(typ.) pull-down resistor connected internally between the EN pin and GND. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 LM2751 www.ti.com SNVS299B – APRIL 2005 – REVISED MAY 2013 ELECTRICAL CHARACTERISTICS(1)(2) (continued) Limits in standard typeface are for TA = 25ºC. Limits in boldface type apply over the full operating ambient temperature range (-40°C ≤ TA ≤ +85°C) . Unless otherwise noted, specifications apply to the LM2751 Typical Application Circuit (pg. 1) with: VIN = 3.6V, V(EN) = VIN, CS0 = CS1 = VIN, C1 = C2 = 1.0µF, CIN = COUT = 2.2µF (3). Symbol tON (5) Parameter VOUT Turn-On Time Conditions (5) Min Typ Max Units 300 µs Turn-on time is measured from when the EN signal is pulled high until the output voltage on VOUT crosses 90% of its final value. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 5 LM2751 SNVS299B – APRIL 2005 – REVISED MAY 2013 www.ti.com BLOCK DIAGRAM LM2751 VIN C1+ GAIN CONTROL 1.2V Ref. SWITCH CONTROL SWITCH ARRAY CS0 G= 2 , C13 2 C2+ FREQ. CTRL CS1 C2- 725 kHz OSC Divider (Div 16, Div 8) 300 kHz VOUT Short-Circuit Protection Thermal Shutdown OSCILLATOR EN EN 6 Enable / Shutdown Control 1.2V Ref. Submit Documentation Feedback Soft-Start Ramp GND Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 LM2751 www.ti.com SNVS299B – APRIL 2005 – REVISED MAY 2013 TYPICAL PERFORMANCE CHARACTERISTICS Unless otherwise specified: TA = 25°C, VIN = 3.6V, CS0 = CS1 = VIN, V(EN) = VIN, CIN = COUT = 2.2µF, C1 = C2 = 1µF. Output Voltage vs. Output Current, Version A (5V), 300kHz Output Voltage vs. Output Current, Version B (4.5V), 300kHz 4.60 VIN = 4.2V 5.08 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 5.10 VIN = 5.5V VIN = 3.3V 5.05 5.03 4.58 VIN = 5.5V VIN = 4.2V 4.56 VIN = 2.8V 4.54 VIN = 3.6V 4.52 VIN = 3.6V VIN = 3.3V VIN = 2.8V 4.50 5.00 0 10 20 30 40 50 60 0 13 26 39 52 65 78 91 104 117 130 70 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) Figure 2. Figure 3. Output Voltage vs. Output Current, Version A (5V), 725kHz Output Voltage vs. Output Current, Version B (4.5V), 725kHz 4.60 VIN = 5.5V 5.06 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 5.08 VIN = 4.2V 5.03 5.01 4.57 VIN = 5.5V VIN = 4.2V 4.54 4.51 VIN = 3.3V VIN = 3.6V 4.48 VIN = 2.8V VIN = 3.6V VIN = 2.8V VIN = 3.3V 4.45 4.98 0 15 30 45 60 75 0 90 20 1.70 40 60 80 100 120 140 160 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) Figure 4. Figure 5. Input Current vs. Input Voltage, Version A (5V) Input Current vs. Input Voltage, Version B (4.5V) 1.5 FSW = 725 kHz IOUT = 0 1.50 FSW = 725 kHz IOUT = 0 1.3 TA = 25°C TA = 25°C IQ (mA) IQ (mA) 1.30 1.10 FSW = 300 kHz 1.1 0.9 0.90 0.7 0.70 FSW = 300 kHz 0.5 0.50 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) Figure 6. Figure 7. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 7 LM2751 SNVS299B – APRIL 2005 – REVISED MAY 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unless otherwise specified: TA = 25°C, VIN = 3.6V, CS0 = CS1 = VIN, V(EN) = VIN, CIN = COUT = 2.2µF, C1 = C2 = 1µF. Output Voltage vs. Input Voltage, Version A (5V), 300kHz Output Voltage vs. Input Voltage, Version B (4.5V), 300kHz 5.09 4.63 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) IOUT = 0 mA 5.07 IOUT = 20 mA 5.04 IOUT = 60 mA 5.02 4.60 IOUT = 0 mA 4.57 IOUT = 40 mA 4.54 IOUT = 120 mA 4.51 IOUT = 70 mA IOUT = 80 mA 4.99 4.48 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 2.7 3.1 INPUT VOLTAGE (V) 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) Figure 8. Figure 9. Output Voltage vs. Input Voltage, Version A (5V), 725kHz Output Voltage vs. Input Voltage, Version B (4.5V), 725kHz 5.09 4.60 5.06 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) IOUT = 0 mA IOUT = 0 mA IOUT = 20 mA 5.03 IOUT = 80 mA 5.00 4.57 4.54 IOUT = 40 mA IOUT = 120 mA 4.51 IOUT = 152 mA 4.48 IOUT = 60 mA 4.97 4.45 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 2.7 3.1 4.3 4.7 5.1 Figure 11. Efficiency vs. Input Voltage, Version A (5V) Efficiency vs. Input Voltage, Version B (4.5V) 100 90 90 80 70 60 50 5.5 80 70 60 50 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) 40 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) Figure 12. 8 3.9 Figure 10. 100 40 2.7 3.5 INPUT VOLTAGE (V) EFFICIENCY (%) EFFICIENCY (%) INPUT VOLTAGE (V) Figure 13. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 LM2751 www.ti.com SNVS299B – APRIL 2005 – REVISED MAY 2013 TYPICAL PERFORMANCE CHARACTERISTICS (continued) Unless otherwise specified: TA = 25°C, VIN = 3.6V, CS0 = CS1 = VIN, V(EN) = VIN, CIN = COUT = 2.2µF, C1 = C2 = 1µF. Output Voltage Ripple vs. Input Voltage Version B (4.5V), Load = 120mA OUTPUT VOLTAGE RIPPLE (mV) 22 Output Voltage Ripple, Version B (4.5V) CIN = 1.0 F COUT: 2.2 F Capacitance, 300 kHz 18 13 COUT: 2.2 F Capacitance, 725 kHz 9 COUT: 10 F Capacitance, 725 kHz COUT: 10 F Capacitance, 300 kHz 4 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) Figure 14. VIN = 3.6V, Load = 150mA CH1: VOUT; Scale: 10mV/Div, AC Coupled Time scale: 400ns/Div Figure 15. Line Step Response, Version B (4.5V) VIN = 3.2V - 4.2V Step, Load = 150mA CH1 (top): VIN; Scale: 1V/Div, DC Coupled CH2: VOUT; Scale: 50mV/Div, AC Coupled Time scale: 200µs/Div Figure 16. VIN = 3.6V, Load = 20mA - 150mA Step CH1 (top): VOUT; Scale: 50mV/Div, AC Coupled CH2: Output Current; Scale: 50mA/Div Time scale: 200µs/Div Figure 17. Start-up Behavior, Version A (5V), Load = 80mA CH1: EN pin; Scale: 2V/Div CH2: VOUT; Scale: 2V/Div Time scale: 100µs/Div Load Step Response, Version B (4.5V) Start-up Behavior, Version B (4.5V), Load = 150mA CH1: EN pin; Scale: 2V/Div CH2: VOUT; Scale: 2V/Div Time scale: 100µs/Div Figure 18. Figure 19. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 9 LM2751 SNVS299B – APRIL 2005 – REVISED MAY 2013 www.ti.com APPLICATION INFORMATION CIRCUIT DESCRIPTION The LM2751 is a Switched Capacitor Convertor with gains of 2x and 1.5x. It is capable of continuously supplying up to 150mA at 4.5V or up to 80mA at 5V depending on the output voltage option. The LM2751's fixed frequency pre-regulation maintains the output voltage to within 3% (typ.), making it well suited for driving White LEDs. There are also four user programmable switching frequencies to reduce the quiescent current consumption at light loads. Aside from powering LEDs, the LM2751 is suitable for driving other devices with power requirements up to 150mA. The LM2751 operates over the extended Li-Ion battery range from 2.8V to 5.5V. The LM2751 limits output current to 250mA (typ.) during an output short circuit condition. LED brightness is controlled by applying a PWM (Pulse Width Modulation) signal to the Enable pin (EN). See PWM BRIGHTNESS CONTROL. SOFT START Soft Start is engaged when the device is taken out of Shutdown mode (EN = logic HIGH) or when voltage is supplied simultaneously to the VIN and EN pins. During Soft Start, the voltage on VOUT will ramp up in proportion to the rate that the reference voltage is being ramped up. The output voltage is programmed to rise from 0V to the regulated output voltage level (4.5V or 5V) in 300µs (typ.). ENABLE MODE The Enable logic pin (EN) disables the part and reduces the quiescent current to 0.77µA (typ.). The LM2751 has an active-high enable pin (LOW = shut down, HIGH = operating) which can be driven with a low-voltage CMOS logic signal (1.5V logic, 1.8V logic, etc). There is an internal 1MΩ pull-down resistor between the EN and GND pins of the LM2751. FREQUENCY MODE SELECT The LM2751 switching frequency is user programmable via two logic input pins, CS0 and CS1. Both logic input pins have active-high logic (LOW = un-selected, HIGH = selected) and can be driven with a low-voltage CMOS logic signal (1.5V logic, 1.8V logic, etc). There are no internal pull-down or pull-up resistors between the CSx and GND pins of the LM2751. The CSO and CS1 can be controlled independently or with the same logic signal. The selectable switching frequencies are 9.5kHz, 37kHz, 300kHz, 725kHz. The switching frequency is programmed according to Table 1. Table 1. Frequency Modes CS0 CS1 Frequency 0 0 37kHz 0 1 300kHz 1 0 9.5kHz 1 1 725kHz VOUT REGULATION The LM2751 uses pre-regulation to regulate the output voltage to 4.5V or 5.0V depending on the voltage option. Pre-regulation uses the voltage present at VOUT to limit the gate drive of the switched capacitor charge pump. This regulation is done before the voltage is gained up by the charge pump, giving rise to the term "preregulation". Pre-regulation helps to reduce input current noise and large input current spikes normally associated with switched capacitor charge pumps. The LM2751 switched capacitor charge pump has gains of 2x and 1.5x. When the input voltage to the device is greater than 3.58V (typ.), the LM2751 operates in a gain of 1.5x. When the input voltage falls below 3.5V (typ.), the device switches to a gain of 2x. 10 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 LM2751 www.ti.com SNVS299B – APRIL 2005 – REVISED MAY 2013 OUTPUT VOLTAGE RIPPLE The primary contributor in keeping the output voltage ripple of the LM2751 low is its switching topology. The output capacitance, input voltage, switching frequency and output current also play a significant part in determining the output voltage ripple. Due to the complexity of the LM2751 operation, providing equations or models to approximate the magnitude of the ripple cannot be easily accomplished. However, the following general statements can be made. The LM2751 has very low output ripple when compared to typical boost regulators due to its double-pump topology, where charge is continually supplied to the output during both 2x and 1.5x modes. Combined with fixed frequency operation modes, double-pumping allows for the use of a very small, low value ceramic capacitor on the output node while still achieving minimal output ripple. Increasing the capacitance by adding a higher value capacitor or placing multiple capacitors in parallel can further reduce the ripple magnitude. CAPACITOR SELECTION The LM2751 requires 4 external capacitors for proper operation. Surface-mount multi-layer ceramic capacitors are recommended. These capacitors are small, inexpensive and have very low equivalent series resistance (ESR, ≤15mΩ typ.). Tantalum capacitors, OS-CON capacitors, and aluminum electrolytic capacitors are generally not recommended for use with the LM2751 due to their high ESR, as compared to ceramic capacitors. For most applications, ceramic capacitors with X7R or X5R temperature characteristic are preferred for use with the LM2751. These capacitors have tight capacitance tolerance (as good as ±10%), hold their value over temperature (X7R: ±15% over −55°C to 125°C; X5R: ±15% over −55°C to 85°C), and typically have little voltage coefficient when compared to other types of capacitors. However selecting a capacitor with a voltage rating much higher than the voltage it will be subjected to, will ensure that the capacitance will stay closer to the capacitor's nominal value. Capacitors with Y5V or Z5U temperature characteristic are generally not recommended for use with the LM2751. Capacitors with these temperature characteristics typically have wide capacitance tolerance (+80%, −20%), vary significantly over temperature (Y5V: +22%, −82% over −30°C to +85°C range; Z5U: +22%, −56% over +10°C to +85°C range), and have poor voltage coefficients. Under some conditions, a nominal 1µF Y5V or Z5U capacitor could have a capacitance of only 0.1µF. Such detrimental deviation is likely to cause Y5V and Z5U capacitors to fail to meet the minimum capacitance requirements of the LM2751. The voltage rating of the output capacitor should be 10V or more. All other capacitors should have a voltage rating at or above the maximum input voltage of the application. DRIVING WHITE LEDS The desired LED current is set by placing a resistor (R) in series with each LED, and is determined by the equation: ILED = (VOUT - VLED) ÷R (1) In the equation above, ILED is the current that flows through a particular LED, and VLED is the forward voltage of the LED at the given current. The output voltage (VOUT) of the LM2751 is tightly regulated to 4.5V or 5V depending on the output voltage option. However, LED forward voltage varies from LED to LED, and LED current will vary accordingly. Mismatch of LED currents will result in brightness mismatch from one LED to the next. Therefore it is suggested that LED groups with tightly controlled I-V characteristics ("Binned" LEDs) be used. LEDs with looser tolerance can be used in applications where brightness matching is not critical, such as in keypad or general backlighting. The typical and maximum diode forward voltage depends highly on the manufacturer and their technology. PWM BRIGHTNESS CONTROL Perceived LED brightness can be adjusted using a PWM control signal on the Enable pin of the LM2751, to turn the voltage output ON and OFF at a rate faster than perceptible by the eye. When this is done, the total brightness perceived is proportional to the duty cycle (D) of the PWM signal (D = the percentage of time that the LED is on in every PWM cycle). A simple example: if the LEDs are driven at 15mA each with a PWM signal that has a 50% duty cycle, perceived LED brightness will be about half as bright as compared to when the LEDs are driven continuously with 15mA. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 11 LM2751 SNVS299B – APRIL 2005 – REVISED MAY 2013 www.ti.com For linear brightness control over the full duty cycle adjustment range, the PWM frequency (f) should be limited to accommodate the turn-on time (typ. TON = 300µs) of the device. D × (1/f) > TON fMAX = DMIN ÷ TON (2) (3) The minimum recommended PWM frequency is 100Hz. Frequencies below this may be visibly noticeable as flicker or blinking. The maximum recommended PWM frequency is 1kHz. Frequencies above this may cause noise in the audible range. THERMAL PROTECTION When the junction temperature exceeds 150°C (typ.), internal thermal protection circuitry disables the device. This feature protects the LM2751 from damage due to excessive power dissipation. The device will recover and operate normally when the junction temperature falls below 140°C (typ.). It is important to have good thermal conduction with a proper layout to reduce thermal resistance. POWER EFFICIENCY Charge-Pump efficiency is derived in the following two ideal equations (supply current and other losses are neglected for simplicity): IIN = G x IOUT E = (VOUT x IOUT) ÷ (VIN x IIN) = VOUT ÷ (G x VIN) (4) (5) In the equations, G represents the charge pump gain. Efficiency is at its highest as G x VIN approaches VOUT. Refer to the efficiency graph in the Typical Performance Characteristics for the detailed efficiency data. POWER DISSIPATION The power dissipation (PDISSIPATION) and junction temperature (TJ) can be approximated with the equations below. PIN is the product of the input current and input voltage, POUT is the power consumed by the load connected to the output, TAis the ambient temperature, and θJA is the junction-to-ambient thermal resistance for the 10-pin SON package. VIN is the input voltage to the LM2751, VVOUT is the voltage at the output of the device, and IOUT is the total current supplied to the load connected to VOUT. PDISSIPATION = PIN - POUT = (VIN × IIN) − (VVOUT × IOUT) TJ = TA + (PDISSIPATION × θJA) (6) (7) (8) The junction temperature rating takes precedence over the ambient temperature rating. The LM2751 may be operated outside the ambient temperature rating, so long as the junction temperature of the device does not exceed the maximum operating rating of 115°C. The maximum ambient temperature rating must be derated in applications where high power dissipation and/or poor thermal resistance causes the junction temperature to exceed 115°C. 12 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 LM2751 www.ti.com SNVS299B – APRIL 2005 – REVISED MAY 2013 REVISION HISTORY Changes from Revision A (May 2013) to Revision B • Page Changed layout of National Data Sheet to TI format .......................................................................................................... 12 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2751 13 PACKAGE OPTION ADDENDUM www.ti.com 7-Oct-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) LM2751SD-A/NOPB ACTIVE WSON DSC 10 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 L145B LM2751SD-B/NOPB ACTIVE WSON DSC 10 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 L146B LM2751SDX-A/NOPB ACTIVE WSON DSC 10 4500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 L145B LM2751SDX-B/NOPB ACTIVE WSON DSC 10 4500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 L146B (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) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. 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Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM2751SD-A/NOPB WSON DSC 10 1000 178.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1 LM2751SD-B/NOPB WSON DSC 10 1000 178.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1 LM2751SDX-A/NOPB WSON DSC 10 4500 330.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1 LM2751SDX-B/NOPB WSON DSC 10 4500 330.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2751SD-A/NOPB WSON DSC 10 1000 210.0 185.0 35.0 LM2751SD-B/NOPB WSON DSC 10 1000 210.0 185.0 35.0 LM2751SDX-A/NOPB WSON DSC 10 4500 367.0 367.0 35.0 LM2751SDX-B/NOPB WSON DSC 10 4500 367.0 367.0 35.0 Pack Materials-Page 2 MECHANICAL DATA DSC0010A SDA10A (Rev A) www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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