LM2750LD-ADJEV

User's Guide SNVA076B – December 2003 – Revised April 2013 AN–1302 LM2750-ADJ Evaluation Board 1 Part Description The LM2750-ADJ is a switched-capacitor doubler that produces a low-noise, well regulated output voltage. With a pair of external resistors, the output voltage can easily be set to a level between 3.8V and 5.2V. The LM2750 is provided in Texas Instruments 10-pin QFN, a package with excellent thermal properties that keeps the part from overheating under almost all rated operating conditions. A perfect fit for space-constrained, battery-powered applications, the LM2750 requires only 3 external components: one input capacitor, one output capacitor, and one flying capacitor. Small, inexpensive ceramic capacitors are recommended for use. These capacitors, in conjunction with the 1.7MHz fixed switching frequency of the LM2750, yield low output voltage ripple, beneficial for systems requiring a lownoise supply. Pre-regulation minimizes input current ripple, reducing input noise to negligible levels. A tightly controlled soft-start feature limits inrush currents during part activation. Shutdown completely disconnects the load from the input. Output current limiting and thermal shutdown circuitry protect both the LM2750 and connected devices in the event of output shorts or excessive current loads. 2 Board Usage 2.1 Input Connect the input and ground pins of the evaluation board to a power supply or battery with short, lowimpedance, low-inductance wires or cables. The nominal input voltage range of the LM2750-ADJ is 2.7V to 5.6V, but at lower output voltages (Vout < 4.9V) the input voltage should never be more than 0.7V below the output voltage. 2.2 Output Voltage and Current The output voltage of the LM2750-ADJ can be programmed with a simple resistor divider (see resistors Rfb1 and Rfb2 on Figure 1). The values of the feedback resistors set the output voltage, as determined by the following equation: Vout = 1.23V × (1 + Rfb1/Rfb2) (1) In Equation 1, the "1.23V" term is the nominal voltage of the feedback pin when the feedback loop is correctly established and the part is operating normally. The sum of the resistance of the two feedback resistors should be between 15kΩ and 20kΩ: 15kΩ < (Rfb1 + Rfb2) < 20kΩ If larger feedback resistors are desired, a 10pF capacitor should be placed in parallel with resistor R1. The output voltage of the LM2750 is ensured to accurate to ±4% when it is set to 5.0V and the part is operated withing nominal operating ratings. Regulation is specified for load currents as high as 120mA. The LM2750 is capable or driving load currents up to and above 120mA. The LM2750 datasheet provides information on high load current usage, and datasheet curves illustrate the typical performance of the part with output currents as high as 175mA. All trademarks are the property of their respective owners. SNVA076B – December 2003 – Revised April 2013 Submit Documentation Feedback AN–1302 LM2750-ADJ Evaluation Board Copyright © 2003–2013, Texas Instruments Incorporated 1 Evaluation Board Schematic 2.3 www.ti.com Shutdown A jumper is present on the evaluation board to bring the LM2750 in and out of shutdown. When the jumper is in place, the SD pin is connected to VIN, and the part is operational. Removing the jumper floats the SD pin. A 200kΩ resistor connected internally between the SD pin and GND pulls the voltage on the SD pin low. This places the LM2750 in shutdown. 3 Evaluation Board Schematic Vin 2.7V to 5.6V Vout 3.8V - 5.2V 1, 2 8, 9 VIN VOUT IOUT up to 120 mA, Cout Cin VIN t 2.9V LM2750-ADJ 4 Jumper SD Rfb1 3 10 FB CAP+ Cfly Rfb2 7 CAPGND 5, 6, DAP Vout = 1.25V × (1 + Rfb1/Rfb2) Figure 1. Evaluation Board Schematic 4 Components 4.1 Integrated Circuit 4.2 Part # Package Mark I.D. Package Dimensions LM2750-ADJ S003B WSON10 (NGY0010A) 3.0mm × 3.0mm × 0.8mm Capacitors Capacitor Symbol (1) 2 Value Case Size U.S. (Metric) Height Temperature Characteristic Mfr. Part # C2012X7R1C225K Cin 2.2µF, 16V (1) 0805 (2012) 1.25mm X5R TDK Cfly 1.0µF, 10V (1) 0603 (1608) 0.8mm X5R TDK C1608X5R1A105K Cout 2.2µF, 16V (1) 0805 (2012) 1.25mm X5R TDK C2012X7R1C225K To meet LM2750 minimum capacitance requirements, 10V is the minimum recommended voltage rating for all capacitors. This elevated rating recommendation accounts for capacitance degradation due to DC bias, a common property of ceramic capacitors. For more information on capacitors, refer to LM2750 Low Noise Switched Capacitor Boost Regulator (SNVS180). AN–1302 LM2750-ADJ Evaluation Board SNVA076B – December 2003 – Revised April 2013 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated References www.ti.com 4.3 Resistors Evaluation Board nominally set to VOUT = 4.5V with the following resistors: 5 Resistor Symbol Value Case Size U.S. (Metric) Manufacturer Part # Rfb1 11.5kΩ, 1% 0603 (1608) Vishay-Dale CRCW06031152F Rfb2 4.42kΩ, 1% 0603 (1608) Vishay-Dale CRCW06034421F References LM2750 Low Noise Switched Capacitor Boost Regulator (SNVS180) AN-1187 Leadless Leadframe Package (LLP) Application Report (SNOA401) SNVA076B – December 2003 – Revised April 2013 Submit Documentation Feedback AN–1302 LM2750-ADJ Evaluation Board Copyright © 2003–2013, Texas Instruments Incorporated 3 Board Layers 6 www.ti.com Board Layers Figure 2. Top Layer, Top View Figure 3. Bottom Layer, Top View (unmirrored) 4 AN–1302 LM2750-ADJ Evaluation Board SNVA076B – December 2003 – Revised April 2013 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated 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. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. 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