LM5007SD-EVAL

User's Guide SNVA073A – May 2004 – Revised April 2013 AN-1298 LM5007 Evaluation Board 1 Introduction The LM5007 evaluation board is designed to provide the design engineer with a fully functional step down switching regulator to evaluate LM5007 regulator IC, in a typical environment. The performance of evaluation board is as follows: • Input range: 12V to 75V • Output voltage: 10V • Output current: 400mA • Measured efficiency: 90% at 300mA and VIN = 30V • Board size: 31.9mm × 44.4mm 2 Theory of Operation The LM5007 Step down switching regulator features all of the functions needed to implement low cost, efficient, Buck bias regulators. This high voltage regulator contains an 80V, 0.7A N-channel Buck switch. The regulator is based on hysteretic control scheme using an on-time inversely proportional to input voltage (VIN). This feature allows the operating frequency to remain relatively constant with load and input voltage variations. The hysteretic control requires no control loop compensation, while providing fast load transient response. Additional protection features include : Thermal Shutdown, VCC undervoltage lockout and maximum duty–cycle limiter. LM5007 can be used in numerous applications to efficiently regulate step down higher voltage inputs. This regulator is well suited for 48V telecom and the new 42V automotive power bus ranges. The LM5007 operates in discontinuous conduction mode at light load currents or continuous conduction mode at heavier load currents. In discontinuous conduction mode, current through the output inductor starts at zero and ramps up to the peak value during the buck switch on time, and then back to zero during buck switch off time. In discontinuous conduction mode, the operating frequency can be relatively low and will vary with load. Therefore at light loads the conversion efficiency is maintained , since switching losses decrease with reduction in switching frequency. The evaluation board just needs one high voltage power-supply (up to 75V and current rating of 1A). The maximum output power is 4 watts. Either an electronic load or resistor bank can be used for testing evaluation board. 3 Start-up Feature There is no soft-start feature in LM5007, and it normally comes up with full load current to supply the power demanded by the load within a short time. The LM5007 contains an intelligent current limit OFF timer intended to reduce the foldback characteristic inherent with fixed off-time over-current protection. If the current in the Buck FET exceeds 725mA the present cycle is immediately terminated (cycle by cycle current limit). Following the termination of the cycle a non-resetable current limit off timer is initiated. The duration of off time is a function of the external setting resistor (Rcl) and the FB pin voltage. When FB pin voltage = 0V the current limit off time is internally preset to 15µs. This condition occurs in short circuit operation when a maximum amount of off time is required. In cases of overload (not complete short circuit) the current limit off time can be reduced as a function of the output voltage (measured at the FB pin). Reducing the off time during smaller overloads reduces the amount of foldback and also reduces the initial start-up time. All trademarks are the property of their respective owners. SNVA073A – May 2004 – Revised April 2013 Submit Documentation Feedback AN-1298 LM5007 Evaluation Board Copyright © 2004–2013, Texas Instruments Incorporated 1 Low Ripple Configuration 4 www.ti.com Low Ripple Configuration For applications where lower output voltage ripple is required the output load can be connected directly to the low ESR output capacitor, as shown in Figure 1. The evaluation board is laid out in such a way that, user can use either (high ripple or low ripple) options by simply shifting the output connector. The series resistor (R) will degrade the load regulation however. Another technique for enhancing the ripple voltage at the FB pin is to place a capacitor in parallel with the feedback divider resistor R1. The addition of the capacitor reduces the attenuation of the ripple voltage from the feedback divider. VIN L SW R1 R FB + + R2 REF 2.5V VOUT COUT LM5007 Figure 1. Low Ripple Configuration 5 Schematic 7V SERIES REGULATOR 12 -75V C1 1P LM5007 VCC 7 8 VIN C5 0.1 P, 100V SD C3 0.1 P THERMAL SHUTDOWN UVLO ON TIMER START R1 200k COMPLETE 6 SD / RON BST Ron START OVER-VOLTAGE COMPARATOR SHUTDOWN + - 2.875V UVLO 300nS MIN OFF TIMER 2 VIN SD C4 0.01P DRIVER COMPLETE LEVEL SHIFT 2.5V SW 100 P L1 1 10V SET + - 5 S FB R REGULATION COMPARATOR FB 3 RCL R2 100k CLR Q R3 3.01k COMPLETE RCL START CURRENT LIMIT OFF TIMER 4 Q + 0.725A BUCK SWITCH CURRENT SENSE R6 1 D1 RTN R4 1k C2 15 P Figure 2. Evaluation Board Schematic Diagram 2 AN-1298 LM5007 Evaluation Board SNVA073A – May 2004 – Revised April 2013 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated Bill of Materials www.ti.com 6 Bill of Materials Table 1. Bill of Materials 7 Item Qty Part Number Description Value C C 1 C4532X7R2A105M CAPACITOR, CER, TDK 1µ, 100V 2 C4532X7R1E156M CAPACITOR, CER, TDK 15µ, 25V C 3 C1206C104K5RAC CAPACITOR, CER, KEMET 0.1µ, 50V C 4 C1206C103K5RAC CAPACITOR, CER, KEMET 0.01µ, 50V C 5 C3216X7R2A104KT CAPACITOR, CER, TDK 0.1µ, 100V D 1 MURA110T3 DIODE, 100V, ON SEMI L 1 SLF7045T-101MR60-1 BUCK INDUCTOR, TDK 100µH R 1 CRCW12062003F RESISTOR 200K R 2 CRCW12061003F RESISTOR 100K R 3 CRCW12063011F RESISTOR 3.01K R 4 CRCW12061001F RESISTOR 1K R 5 CRCW12061R00F RESISTOR 1 U 1 LM5007 REGULATOR, TEXAS INSTRUMENTS Efficiency Measurements Normal Operation VIN = 40V, VOUT = 10V, Load Resistance = 20Ω LM5007 10V Output Efficiency 100 1 95 2 Ps 5.0V VIN = 15V CH1 - Output Voltage CH2 - Switch Node Voltage CH3 - Inductor Current EFFICIENCY (%) 90 2 2 Ps 20.0V 85 80 VIN = 30V 3 VIN = 50V 75 3 2 2 Ps 200 mA VIN = 70V 70 65 1 60 0 0.1 0.2 0.3 0.4 0.5 LOAD (A) SNVA073A – May 2004 – Revised April 2013 Submit Documentation Feedback AN-1298 LM5007 Evaluation Board Copyright © 2004–2013, Texas Instruments Incorporated 3 Efficiency Measurements www.ti.com Start-up Behavior VIN = 40V, Load Resistance = 20Ω Load Transient VIN = 15V, VOUT = 10V, Load change from 20Ω to 120Ω CH1 - Output Voltage CH2 - Switch Node Voltage CH3 - Inductor Current 1 1 2 Ps 5.0V 20 Ps 5.0V CH1 - Output Voltage CH2 - Switch Node Voltage CH3 - Inductor Current 2 20 Ps 10.0V 2 2 Ps 20.0V 3 2 3 3 20 Ps 200 mA 2 3 2 Ps 200 mA 1 1 Input Voltage vs Switching Frequency 430 400 410 SWITCHING FREQUENCY (kHz) SWITCHING FREQUENCY (kHz) Load Current vs Switching Frequency 450 350 300 250 200 150 100 50 390 370 350 330 310 290 270 250 0 0 200 400 600 0 LOAD CURRENT (mA) 4 AN-1298 LM5007 Evaluation Board 20 40 60 80 INPUT VOLTAGE (V) SNVA073A – May 2004 – Revised April 2013 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated PCB Layouts www.ti.com 8 PCB Layouts Figure 3. Top Layer Figure 4. Silk Screen SNVA073A – May 2004 – Revised April 2013 Submit Documentation Feedback AN-1298 LM5007 Evaluation Board Copyright © 2004–2013, Texas Instruments Incorporated 5 PCB Layouts www.ti.com Figure 5. Bottom Layer Figure 6. Top Soldermask 6 AN-1298 LM5007 Evaluation Board SNVA073A – May 2004 – Revised April 2013 Submit Documentation Feedback Copyright © 2004–2013, 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. 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