Application Report SLUA268 - April 2001 2.5-V to 5.0-V, 600-kHz High-Efficiency Synchronous Boost Converter With TPS43000 PWM Controller Sopie Chen System Power ABSTRACT The application report describes the functionalities of the cTPS43000 controller and explains the design procedures of a step-up application from 2.5 V to 5.0 V. Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 Design Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 PCB Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 List of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 List of Figures 1 Schematic of PMP144 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 Power Stage Gain and Phase vs Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Efficiency vs Load Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Typical Operation Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Output Ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6 Transient Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7 Top Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7 Bottom Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 List of Tables 1 List of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Trademarks are the property of their respective owners. 1 1 Introduction The TPS43000 is a high-frequency, voltage-mode, synchronous PWM controller that can be flexibly used in buck, boost, buck-boost, and SEPIC topologies. This full-featured controller is designed to drive a pair of external MOSFETs (N/P) and can be used with a wide range of output voltages and power level. It can be widely used in networking equipment, servers, PDAs, cellular phones, and telecommunication applications. A schematic of this board is shown in Figure 1. Recommended parts list is provided in Table 1. The layout of the PCB board is shown in Figure 7. The specification for this board is as follows: • VIN = 2.5 V ±10% • VOUT = 5.0 V • IOUT = 0.2 A to 4 A, nominal current is 3 A and enters PFM at 1 A. • Ripple = 1% • Efficiency > 90% + + + Figure 1. Schematic of PMP144 2 2.5-V to 5.0-V, 600-kHz High-Efficiency Synchronous Boost Converter With TPS43000 PWM Controller 2 Design Procedure 2.1 Frequency Setting The TPS43000 operates either in constant frequency, or in an automatic PFM mode. In the automatic PFM mode, the controller goes to sleep when the inductor current goes discontinuous, and wakes up when the output voltage has fallen by 2%. Refer to the TPS43000 datasheet (TI literature number SLUS489) for more detail. The PFM mode is used in this application. The converter operates at fixed 600 kHz above 1 A and enters into PFM at 1 A. A resistor R4, which is connected from the RT pin to ground, programs the oscillator frequency. The approximate operating frequency is calculated in equation (1). f ( MHz ) + 38 R4( kW ) (1) R4 = 63.4 kΩ is chosen for 600 kHz operation. 2.2 Inductance Value The inductance value is calculated in equation (2). L MIN + V OUT f (1 * D) D 2 2 (2) I OUTǒminǓ IRIPPLE is the ripple current flowing through the inductor, which affects the output voltage ripple and core losses. Based on the requirement to enter PFM at 1 A and 600 kHz, the inductance value is calculated as 0.52 µH and a 0.6-µH inductor is used. 2.3 Input and Output Capacitors The output capacitance and its ESR needed is calculated in equations (3) and (4). C OUTPUTǒminǓ + ESR OUT + I OUT(max) f D MAX (3) V RIPPLE V RIPPLE I INǒ ripple Ǔ OUTǒmaxǓ ) 2 1*D MAX I (4) With 1% output voltage ripple, the required capacitance is at least 73 µF and its ESR should be less than 5 mΩ. In order to meet the 1% output ripple requirement, at least four Panasonic 6.3-V/150-µF capacitors, whose ESR is 18 mΩ, are needed. Instead of using four expensive low-ESR capacitors, two capacitors (C8 and C9) are used and a second L-C filter (L2 and C10) is used to filter output voltage. The secondary L-C filter parameters are L2: FB784729 from GCI and C10 = 10 µF 2.5-V to 5.0-V, 600-kHz High-Efficiency Synchronous Boost Converter With TPS43000 PWM Controller 3 The input capacitance is calculated in equation (5). The calculated value is about 65 µF and a 150-µF low-ESR specialty polymer, (SP), capacitor is used. C INǒminǓ + I INǒ ripple Ǔ 2.4 D MAX TS (5) V INǒ ripple Ǔ Compensation Design For the boost converter, there is a right-half-plane (RHP) zero, which moves with operating conditions. The system phase starts to drop off a decade before this zero, limiting the system’s bandwidth. In this circuit, the RHP zero is around 88 kHz. The L-C frequency of the power stage, ƒC, is around 6.0 kHz and the ESR zero is around 70.7 kHz, as shown in Figure 2. The overall crossover frequency, ƒ0db, is chosen at 10 kHz for reasonable transient response and stability. R1 to R3 and C1 to C3 combine to form a Type III compensator network. Both zeros, ƒZ1 and ƒZ2, from the compensator are set at 0.5 ƒC to compensate the phase delay caused by RHP zero. The two poles ƒP1 and ƒP2 and are set at ESR zero and half of switching frequency separately. The frequency of poles and zeros are defined by the following equations: f Z1 + 2 p 1 R2 C1 f P1 + 2 p 1 R3 C3 ; f Z2 [ 2 p 1 R1 C3 ; f P2 [ 2 p 1 R2 C2 , assuming R1 ơ R3 (6) , assuming C1 ơ C2 (7) The compensator values are shown below: C1 = 4700 F, C2 = 68 pF, C3 = 270 pF, R1 = 100 kΩ, R2 = 9.09 kΩ; R3 = 9.09 kΩ. POWER STAGE GAIN AND PHASE vs FREQUENCY 100 100 70 70 40 40 10 10 −20 −20 −50 −50 −80 −80 Phase −110 −110 −140 −140 −170 −170 −200 −200 10 Phase − Degree Gain − db Gain 100 1k 10 k 100 k 1M f − Frequency − Hz Figure 2. 4 2.5-V to 5.0-V, 600-kHz High-Efficiency Synchronous Boost Converter With TPS43000 PWM Controller 2.5 MOSFETS and Diode For a 5-V output voltage, the lower the RDS(on) of the MOSFET, the higher the efficiency. Si4486 (RDS(on) = 10 mΩ) and Si4403DV (RDS(on) = 20 mΩ) are chosen. MBRS340T3 is used for a parallel diode with Q2. 2.6 Voltage Sense Resistor R1 and R6 operate as the output voltage divider. The internal reference voltage is 0.8 V. The relationship between the output voltage and divider is described in equation (8). V REF R6 + V OUT (8) R1 ) R6 Setting resistor R1 to 100 kΩ using a value of 5.0-V output regulation, R6 is calculated as 19.1 kΩ. 3 Test Results 3.1 Efficiency Curves Efficiency tested at different loads and input voltages are shown in Figure 3. The maximum efficiency is as high as 91.8% at light load. This comes from the PFM function and the losses from driving the gate are reduced significantly. EFFICIENCY vs LOAD CURRENT 92 VIN = 2.75 V Efficiency − % 90 88 VIN = 2.5 V 86 VIN = 2.25 V 84 0.0 0.5 1.0 1.5 2 2.5 3.0 3.5 4.0 ILOAD −Load Current − A Figure 3. 2.5-V to 5.0-V, 600-kHz High-Efficiency Synchronous Boost Converter With TPS43000 PWM Controller 5 3.2 Typical Operation Waveform Typical operation waveform is shown in Figure 4 with VIN = 2.5 and IOUT = 3.0 A. TYPICAL OPERATION VDS(Q1) (5.0 V/div) VGS(Q2) (5.0 V/div) VGS(Q1) (5.0 V/div) t − Time − 500 ns/div Figure 4. 3.3 Transient Response and Output Ripple Voltage The output ripple is approximately 18.6 mV peak-to-peak with a 3.0-A output. When the load changes from 2.4 A to 3.0 A, the overshooting voltage is approximately 76 mV. OUTPUT RIPPLE TRANSIENT RESPONSE VOUT (100 mV/div) VOUT(ac) (10 mV/div) IOUT (1 A/div) t − Time − 500 ns/div Figure 5. 6 t − Time − 1 ms/div Figure 6. 2.5-V to 5.0-V, 600-kHz High-Efficiency Synchronous Boost Converter With TPS43000 PWM Controller 4 PCB layout Figures 7 and 8 show the PCB layout and the photo of a built-up board. All components are on the top side of the board. The bottom side of the board is the ground plane. The PWB is made large to dissipate the losses. Figure 7. Top Side Figure 8. Bottom Side 2.5-V to 5.0-V, 600-kHz High-Efficiency Synchronous Boost Converter With TPS43000 PWM Controller 7 5 List of Materials Table 1 lists board components and their values, which can be modified to meet the application requirements. Table 1. List of Materials Reference Capacitor Qty Description Manufacturer Part Number C1 1 Ceramic, 4.7 nF, 16 V, X7R, 10%, 603 Murata GRM219R71C472K C2 1 Ceramic, 68 pF, 50 V, COG, 5%, 603 Murata GRM1885C1H680J C3 1 Ceramic, 270 pF, 50 V, COG, 5%, 603 Murata GRM1885C1H271J C4, C5, C6 3 Ceramic, 0.47 µF, 16 V, X7R, 10%, 805 Murata GRM219R71C474K C9 2 Ceramic, 10 µF, 6.3 V, 20%, 1210 Taiyo−yuden JMK325BJ106MM C7, C8, C10 3 150 µF, 6.3 V, 18 mΩ, 20%, 7343 (D) Panasonic EEFUE0J151R Diode, Schottky D1 1 3 A, 40 V, SMC On Semiconductor MBRS340 Terminal Block J1, J2 2 2-pin, 6 A, 3.5 mm, 0.27 x 0.25”” OST ED1514 Inductor L1 1 SMT, 0.6 µH, 24 A, 6 mΩ, 13.5 mm x 6 mm Sumida CEP12D38−0R6 Ferrite L2 1 Bead, 0.9 mΩ DCR, 48 Ω at 25 Mhz, 12.25 mm x 5 mm GCI Technologies FB784729 Resistor R1 1 Chip, 100 kΩ, 1/16 W, 1%, 603 Std Std R2, R3 2 Chip, 9.09 kΩ, 1/16 W, 1%, 603 Std Std R4 1 Chip, 63.4 kΩ, 1/16 W, 1%, 603 Std Std R5 1 Chip, 1.00 kΩ, 1/16 W, 1%, 603 Std Std R6 1 Chip, 19.1 kΩ, 1/16 W, 1%, 603 Std Std R7 1 Chip, 49.9 Ω, 1/16 W, 1%, 603 Std Std Q2 1 P-channel, 1.8 Vgs, 9 A, 17 mΩ, SO−8 Siliconix Si4403DY Q1 1 N-channel, 2.5 Vgs, 17 A, 10 mΩ, SO−8 Siliconix Si4866DY IC U1 1 Multi-topology high-frequency, PWM controller, TSSOP−16 Texas Instruments TPS43000PW Test Point TP1, TP2, TP3, TP4, TP5, TP6 6 Black, 1mm, 0.038” Farnell 240−333 N/A 1 FR4, 0.032, SMOBC any PMP144 MOSFET PCB 8 2.5-V to 5.0-V, 600-kHz High-Efficiency Synchronous Boost Converter With TPS43000 PWM Controller IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Applications Amplifiers amplifier.ti.com Audio www.ti.com/audio Data Converters dataconverter.ti.com Automotive www.ti.com/automotive DSP dsp.ti.com Broadband www.ti.com/broadband Interface interface.ti.com Digital Control www.ti.com/digitalcontrol Logic logic.ti.com Military www.ti.com/military Power Mgmt power.ti.com Optical Networking www.ti.com/opticalnetwork Microcontrollers microcontroller.ti.com Security www.ti.com/security Telephony www.ti.com/telephony Video & Imaging www.ti.com/video Wireless www.ti.com/wireless Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright 2004, Texas Instruments Incorporated