LM3676SD-ADJEV

User's Guide SNVA191D – December 2006 – Revised April 2013 AN-1536 LM3676 Evaluation Board 1 Introduction The LM3676 evaluation board is a working demonstration of a step down DC-DC converter. This application note contains information about the evaluation board. For further information on buck converter topology, device electrical characteristics, and component selection please refer to the LM3676 2-MHz 600-mA Step-Down DC-DC Converter With Mode Control (SNVS426). 2 General Description The LM3676 converts high input voltages to lower output voltages with high efficiency through an inductor based switching topology. The LM3676 has a mode-control pin that allows the user to select continuous Forced PWM mode over the complete load range or an intelligent Auto, PFM-PWM, mode that changes modes depending on the load. Setting the Mode pin low (1.0V) the part offers superior efficiency under high load conditions (>100mA) and the lowest output noise performance during Forced PWM. The LM3676 is available in both fixed and adjustable output voltage options ranging from 1.0V to 3.3V in a 8lead non-pullback WSON package (3mm × 3mm). 3 Operating Conditions • • • • 4 VIN range: 2.9V ≤ VIN ≤ 5.5V Recommended load current: 0 mA ≤ IOUT ≤ 600 mA Ambient temperature (TA) range: -30C to +85C Junction temperature (TJ) range: -30C to +125C Typical Application VIN 2.9V to 5.5V L1: 2.2 PH VIN 8 CIN 4.7 PF 2 SW LM3676 PGND 1 NC 4 6 7 EN 5 3 FB VOUT COUT 10 PF SGND MODE Figure 1. Typical Application Circuit: Fixed Voltage All trademarks are the property of their respective owners. SNVA191D – December 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1536 LM3676 Evaluation Board 1 Output Voltage Selection for LM3676SD-ADJ www.ti.com VIN VIN 2.9V to 5.5V L1: 2.2 PH LM3676ADJ 4 CIN 4.7 PF 2 8 PGND 1 7 NC EN VOUT SW COUT FB R1 C1 10 PF SGND C2 R2 6 3 5 MODE Figure 2. Typical Application Circuit: Adjustable Voltage 5 Output Voltage Selection for LM3676SD-ADJ The output voltage of the adjustable parts can be programmed through the resistor network connected from VOUT to FB to GND. The resistor from FB to GND (R2) should be 200kΩ to keep the current drawn through this network small, but large enough that it is not susceptible to noise. If R2 is 200kΩ, and given the VFB is 0.5V, then the current through the resistor feedback network will be 2.5µA. The output voltage formula is: VOUT = VFB R1 (R ) +1 2 (1) where: VOUT = output voltage (V) VFB = feedback voltage (0.5V typical) R1 = feedback resistor from VOUT to FB(Ω ) R2 = feedback resistor from FB to GND (Ω) For the fixed output voltage parts, the feedback resistors are internal. The bypass capacitors C1 and C2 in parallel with the feedback resistors are chosen for stable operation. Following are the formulas for C1 and C2: C1 = 1 2 x S x R1 x 45 kHz (2) C2 = 1 2 x S x R2 x 45 kHz (3) Table 1. LM3676-ADJ Configurations for Various Vout (Circuit of Figure 2) 2 VOUT (V) R1(kΩ ) R2(kΩ ) C1(pF) C2(pF) L (µH) CIN (µF) COUT (µF) 1.0 200 200 18 None 2.2 4.7 10 1.1 191 158 18 None 2.2 4.7 10 1.2 280 200 12 None 2.2 4.7 10 1.5 357 178 10 None 2.2 4.7 10 1.6 442 200 8.2 None 2.2 4.7 10 1.7 432 178 8.2 None 2.2 4.7 10 1.8 464 178 8.2 None 2.2 4.7 10 1.875 523 191 6.8 None 2.2 4.7 10 2.5 402 100 8.2 None 2.2 4.7 10 2.8 464 100 8.2 33 2.2 4.7 10 3.3 562 100 6.8 33 2.2 4.7 10 AN-1536 LM3676 Evaluation Board SNVA191D – December 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Powering the LM3676 for Bench Measurement www.ti.com 6 Powering the LM3676 for Bench Measurement When powering the LM3676 with a bench power supply, it is recommended to place a 100µF tantalum capacitor across the VIN and GND supply terminals of the bench power supply. This capacitor will reduce the input spike caused by the power supply and long power cables. The combination of the power supply and inductance within the power cables produce a large voltage spike that may damage the device. In addition, consideration must given to the enable pin of the device. The enable should never be taken high, until minimum specified operating voltage of 2.7V is reached. The enable pin should also never exceed the input voltage. 7 Connection Diagram and Package Mark Information PGND 1 8 VIN SW 2 7 SGND MODE 3 6 NC FB 4 5 EN Figure 3. WSON, Top View 8 Pin Descriptions (8-lead Non-Pullback WSON Package) Pin # Name Description 1 PGND Power supply input. 2 SW 3 MODE 4 FB Feedback analog input. Connect directly to the output filter capacitor for fixed voltage versions. For adjustable version external resistor dividers are required (Figure 2). The internal resistor dividers are disabled for the adjustable version. 5 EN Enable pin. The device is in shutdown mode when voltage to this pin is 1.0V. Do not leave this pin floating. 6 NC Not Connected. Keep Pin floating 7 SGND 8 VIN Switching node connection to the internal PFET switch and NFET synchronous rectifier. Mode Control Pin: > 1.0V selects continous PWM mode ; < 0.4V selects Auto (PFM-PWM) mode. Do not leave this pin floating. Signal Ground Pin. Power Supply input. Connect to the input filter capacitor (Figure 1). SNVA191D – December 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1536 LM3676 Evaluation Board 3 Evaluation Board Layout 9 www.ti.com Evaluation Board Layout Figure 4. Top Layer (WSON-8 pin) Figure 5. Bottom Layer (WSON-8 pin) 4 AN-1536 LM3676 Evaluation Board SNVA191D – December 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Bill of Materials for Common Configurations www.ti.com 10 Bill of Materials for Common Configurations Part Manufacture Manufacture # Description LM3676 - 3.3V Adjustable Texas Instruments C1 (input C) TDK C2012XR0J475K 4.7µF, 6.3V, 0805, 10% C2 (output C) TDK C2012X5R0J106K 10µF, 6.3V, 0805, 10% L1 (inductor) Coilcraft DO3314-222MX 2.2µH inductor, 1.6A sat R1 (VOUT to VFB ) Vishay CRCW06035623F 562kΩ, 0603, 1% R2 (VFB to GND) Vishay CRCW06031003F 100kΩ, 0603, 1% C3 (VOUT to VFB ) Vishay VJ0603A6R8KXAA 6.8pF, 0603, 10% C4 (VFB to GND) Vishay VJ0603A330KXAA 33pF , 0603, 10% VIN banana jack - red Johnson Components 108-0902-001 connector, insulated banana jack (red) VOUT banana jack - yellow Johnson Components 108-0907-001 connector, insulated banana jack (yellow) GND banana jack - black Johnson Components 108-0903-001 connector, insulated banana jack (black) Post for EN Turrent 1573-2 Upright post from eval board Post for VIN Turrent 1502-2 Upright post from eval board Post for VOUT Turrent 1502-2 Upright post from eval board Post for GND Turrent 1502-2 Upright post from eval board SNVA191D – December 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1536 LM3676 Evaluation Board 5 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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