TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 TWO-PHASE, SYNCHRONOUS BUCK CONTROLLER WITH INTEGRATED MOSFET DRIVERS FEATURES APPLICATIONS • • • • • • Point-of-Load Converter Graphic Cards Internet Servers Networking Equipment Telecommunications Equipment DC Power Distributed Systems SW2 PGND LDRV2 VIN5 LDRV1 HDRV1 SW1 HDRV2 BOOT2 3 UVLO 4 21 BP5 5 20 AGND 6 19 CS2 CSRT1 7 18 CSRT2 COMP 8 17 9 10 11 12 13 14 15 16 DIFFO CS1 RT PGOOD VOUT GSNS ILIM SS 22 EN/SYNC 2 23 BP8 • • • • • OVSET 32 31 30 29 28 27 26 25 24 1 VDD • • BOOT1 FB • RHB PACKAGE (TOP VIEW) +EA • • Supports 5-V Output Two-Phase Interleaved Operation Operates With Pre-Biased Outputs 1-V to 40-V Power Stage Operation Range Requires VIN5 @ 50 mA (typ) Depending on External MOSFETs and Switching Frequency 10-µA Shutdown Current Programmable Switching Frequency up to 1 MHz/Phase Current Mode Control with Forced Current Sharing Better than 1% Internal 0.7-V Reference Resistive Divider Sets Direct Output Over Voltage Threshold. Programmable Input Undervoltage Lockout True Remote Sensing Differential Amplifier Resistive or Inductor’s DCR Current Sensing 32-Pin QFN Package Can Be Used with TPS40120 to Provide a 6-Bit Digitally Controlled Output VREF • • • • • DESCRIPTION The TPS40131 is a two-phase synchronous buck controller that is optimized for low-output voltage, high-output current applications powered from a supply between 1 V and 40 V. A multi-phase converter offers several advantages over a single power stage including lower current ripple on the input and output capacitors, faster transient response to load steps, improved power handling capabilities, and higher system efficiency. Each phase can be operated at a switching frequency up to 1 MHz, resulting in an effective ripple frequency of up to 2 MHz at the input and the output. The two phases operates 180 degrees out-of-phase. 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. 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 © 2007, Texas Instruments Incorporated TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 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. SIMPLIFIED APPLICATION DIAGRAM CS1 CSRT1 CSRT2 CS2 VOUT VIN1 VIN1 5V 5V 32 31 30 29 28 27 26 25 HDRV1 SW1 VIN5 LDRV1 PGND LDRV2 SW2 HDRV2 5V VOUT 1 BOOT` BOOT2 24 2 OVSET SS 23 3 VOUT 4 GSNS 5 DIFFO CS1 6 CS1 CSRT1 7 CSRT1 CSRT2 18 8 COMP RT 17 VOUT 5 V VIN1 UVLO 22 LOAD BP5 21 TPS40131 AGND 20 VREF +EA FB VDD BP8 EN/SYNC ILIM PGOOD CS2 19 9 10 11 12 13 14 15 16 CS2 CSRT2 VREF UDG-07030 2 Submit Documentation Feedback TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 ORDERING INFORMATION TA PACKAGE -40°C to 85°C Plastic QFN(RHB) PART NUMBER TAPE AND REEL QUANTITY TPS40131RHBT 250 TPS40131RHBR 3000 ABSOLUTE MAXIMUM RATING over operating free-air temperature range unless otherwise noted TPS40131 VDD -1 to 30 DIFFO, VOUT Input voltage range VBP8 SW1, SW2 -1 to 44 BP8 -1 to 10 BOOT1, BOOT2, HDRV1, HDRV2 All other pins Sourcing current UNITS V -0.3 to VSW + 6.0 -0.3 to 6.0 RT 200 TJ Operating junction temperature range -40 to 125 Tstg Storage temperature -55 to 150 Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds µA °C 260 RECOMMENDED OPERATING CONDITIONS over operating free-air temperature range unless otherwise noted (1) TPS40131 Input voltage range VDD 4.5 to 28 DIFFO, VOUT (VBP8-1) SW1, SW2 -1 to 44 BP8 -1 to 8 BOOT1, BOOT2, HDRV1, HDRV2 All other pins Sourcing current V -0.3 to VSW + 5.5 -0.3 to 5.5 RT 200 TJ Operating junction temperature range -40 to 85 Tstg Storage temperature -55 to 150 Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds (1) UNITS µA °C 260 Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. Submit Documentation Feedback 3 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 ELECTRICAL CHARACTERISTICS TA = -40°C to 85°C, VIN = 5.0 V, VDD = 12.0 V, RRT = 64.9 kΩ, TJ = TA (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 4.5 5.0 5.8 5 µA 1.0 2.0 mA 5.0 5.5 3 5 4.25 4.45 VIN5 INPUT SUPPLY VIN Operating voltage range, VIN5 IIN Shutdown current, VIN5 EN/SYNC = GND Operating current Outputs switching, No load V BP5 INPUT SUPPLY Operating voltage range IBP5 Operating current 4.3 Outputs switching, no external FETs Turn-on BP5 rising Turn-off 3.90 hysteresis (1) VDD INPUT SUPPLY BP8VBP8 Output Voltage 150 4.5 Internal load < 1 mA, No external load V mA V mV 28 7.5 V V OSCILLATOR/SYNCHRONIZATION Phase frequency accuracy RT = 64.9 kΩ 355 400 RT = 64.9 kΩ, 0°C ≤ TJ≤ 85°C 360 400 455 440 Phase frequency set range (1) 100 1200 Synchronization frequency range (1) 800 9600 Synchronization input threshold (1) VBP5/2 kHz V EN/SYNC Enable threshold Pulse width > 50 ns 0.8 Voltage capability (1) 1.0 1.5 VBP5 V PWM Maximum duty cycle per channel (1) 87.5% Minimum duty cycle per channel (1) 0 VREF Voltage reference ILOAD = 100 uA 0.687 0.700 0.709 V ERROR AMPLIFIER VFB Voltage feedback, trimmed (including differential amplifier) 0.691 0.700 0.705 VFB Voltage feedback, without differential amplifier 0.687 0.700 0.710 CMRR Input common mode range (1) 0.0 0.7 2.0 55 200 Input bias current VFB = 0.7 V Input offset voltage nA V ISRC Output source current VCOMP = 1.1 V, VFB = 0.6 V 1 2 ISINK Output sink current VCOMP = 1.1 V, VFB =VBP5 1 2 VOH High-level output voltage ICOMP = -1 mA 2.5 2.9 VOL low-level output voltage ICOMP = 1 mA GBW Gain bandwidth (1) 3 5 MHz AVOL Open loop gain (1) 60 90 dB (1) 4 0 V Ensured by design. Not production tested. Submit Documentation Feedback 0.5 mA 0.8 V TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 ELECTRICAL CHARACTERISTICS (continued) TA = -40°C to 85°C, VIN = 5.0 V, VDD = 12.0 V, RRT = 64.9 kΩ, TJ = TA (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 3.0 5.0 7.0 µA 500 Ω 0.95 1.00 1.05 V -15 -3 10 SOFT START ISS Soft-start source current RSS Soft-start pull down resistance VSS Fault enable threshold voltage 32 clocks after EN/SYNC before SS current begins CURRENT SENSE AMPLIFIER Input offset voltage CS1, CS2 Gain transfer to PWM comparator -100 mV ≤ VCS≤ 100 mV, VCSRT = 1.5 V Gain variance between phases VCS - VCSRTn = 100 mV Input offset variance between phases VCS = 0 V Input common mode (2) Bandwidth (2) 5 mV V/V -6% 0 6% -6 0 6 0 1 VBP8-0.7 18 mV V MHz DIFFERENTIAL AMPLIFIER Gain CMRR 1 Gain tolerance VOUT = 5.5 V vs VOUT = 0.7 V, VGSNS = 0 V Common mode rejection ratio 0.7 V≤ VOUT ≤ 5.5 V Output source current VOUT - VGSNS = 2.0 V, VDIFFO≥ 1.95 V 2 4 Output sink current VOUT - VGSNS = 2.0 V, VDIFFO≥ 2.05 V 2 4 Bandwidth (2) -0.5% V/V 0.5% 50 dB mA 5 MHz Input impedance, non-inverting (2) VOUT to GND 40 Input impedance, inverting (2) 40 VGSNS to VDIFFO kΩ GATE DRIVERS Source on-resistance, HDRV1, HDRV2 VBOOT1 = 5 V, VBOOT2 = 5 V, VSW1 = 0 V, VSW2 = 0 V, Sourcing 100 mA 1.0 2.0 3.5 Sink on-resistance, HDRV1, HDRV2 VBOOT1 = 5 V, VBOOT2 = 5 V, VVIN5 = 5 V, VSW1 = 0 V, VSW2 = 0 V, Sinking 100 mA 0.5 1.0 2.0 Source on-resistance, LDRV1, LDRV2 VVIN5 = 5 V, VSW1 = 0 V, VSW2 = 0 V, Sourcing 100 mA 1 2 3.5 Sink on-resistance, LDRV1, LDRV2 VVIN5 = 5 V, VSW1 = 0 V, VSW2 = 0 V, Sinking 100 mA 0.30 0.75 1.50 tRISE Rise time, HDRV (2) CLOAD = 3.3 nF 25 75 tFALL Fall time, HDRV (2) CLOAD = 3.3 nF 25 75 tRISE Rise time, LDRV (2) CLOAD = 3.3 nF 25 75 tFALL Fall time, LDRV (2) CLOAD = 3.3 nF 25 60 ns SW falling to LDRV rising 50 mV tDEAD Dead time (2) tON Minimum controllable on-time (2) Ω Ω LDRV falling to SW rising 30 CLOAD = 3.3 nF 150 OUTPUT UNDERVOLTAGE FAULT Undervoltage fault threshold VFB relative to GND 560 588 610 -20% -16% -13% VOVSET relative to GND 800 820 840 VOVSET relative to VVREF 15% 16% 20% VFB relative to VVREF OUTPUT OVERVOLTAGE SET Overvoltage threshold (2) mV Ensured by design. Not production tested. Submit Documentation Feedback 5 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 ELECTRICAL CHARACTERISTICS (continued) TA = -40°C to 85°C, VIN = 5.0 V, VDD = 12.0 V, RRT = 64.9 kΩ, TJ = TA (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX 0.4 0.5 0.6 UNIT RAMP Ramp amplitude (3) Ramp valley (3) 1.4 V POWER GOOD PGOOD high threshold VFB relative to VREF 10% 14% PGOOD low threshold VFB relative to VREF -14% -10% VOL Low-level output voltage IPGOOD = 4 mA ILEAK PGOOD bias current VPGOOD = 5.0 V 0.35 0.60 V 50 80 µA 1.0 1.1 INPUT UVLO PROGRAMMABLE Input threshold voltage, turn-on 0.9 Input threshold voltage, turn-off (3) 6 0.810 Ensured by design. Not production tested. Submit Documentation Feedback V TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 SW2 HDRV2 PGND LDRV2 32 31 30 29 28 27 26 25 24 1 BOOT2 BP5 5 20 AGND 6 19 CS2 CSRT1 7 18 CSRT2 COMP 8 17 9 10 11 12 13 14 15 16 VREF CS1 RT PGOOD DIFFO ILIM 4 EN/SYNC UVLO 21 BP8 3 VOUT GSNS VDD SS 22 FB 2 23 +EA OVSET VIN5 LDRV1 HDRV1 BOOT1 SW1 RHB PACKAGE (TOP VIEW) Terminal Functions TERMINAL NAME NO. I/O DESCRIPTION AGND 20 - Low noise ground connection to the device. BOOT1 1 I Provides a bootstrapped supply for the high-side FET driver for PWM1, enabling the gate of the high-side FET to be driven above the input supply rail. Connect a capacitor from this pin to SW1 pin and a Schottky diode from this pin to VIN5. BOOT2 24 I Provides a bootstrapped supply for the high-side FET driver for PWM2, enabling the gate of the high-side FET to be driven above the input supply rail. Connect a capacitor from this pin to SW2 pin and a Schottky diode from this pin to VIN5. BP5 21 O Filtered input from the VIN5 pin. A 10-Ω resistor should be connected between VIN5 and BP5 and a 1.0-µF ceramic capacitor should be connected from this pin to ground. BP8 13 O Output of the LDO that powers the differential amplifer and the current sense amplifiers. The voltage is approximately (VVDD -0.2 V) until the output regulates at approximately 7.5 V. Decouple this pin with a minimum capacitance of 1.0-µF to GND. COMP 8 O Output of the error amplifier. The voltage at this pin determines the duty cycle for the PWM. CS1 6 I CS2 19 I These pins are used to sense the inductor phase current. Inductor current can be sensed with an external current sense resistor or by using an external R-C circuit and the inductor's DC resistance. The traces for these signals must be connected directly at the current sense element. See Layout Guidelines for more information. CSRT1 7 O CSRT2 18 O DIFFO 5 O Output of the differential amplifier. The voltage at this pin represents the true output voltage without IR drops that result from high-current in the PCB traces. The VOUT and GSNS pins must be connected directly at the point of load where regulation is required. See Layout Guidelines for more information. +EA 10 I This is the input to the non-inverting input of the Error Amplifier. This pin is normally connected to the VREF pin and is the voltage that the feedback loop regulates to. EN/SYNC 14 I A logic high signal on this input enables the controller operation. A pulsing signal to this pin synchronizes the rising edge of SW to the falling edge of an external clock source. FB 11 I Inverting input of the error amplifier. In closed loop operation, the voltage at this pin is the internal reference level of 700 mV. This pin is also used for the PGOOD and undervoltage comparators. GSNS 4 I Inverting input of the differential amplifier. This pin should be connected to ground at the point of load. HDRV1 32 O Gate drive output for the high-side N-channel MOSFET switch for PWM1. Output is referenced to SW1 and is bootstrapped for enhancement of the high-side switch. Return point of current sense voltage. The traces for these signals must be connected directly at the current sense element. See Layout Guidelines for more information. Submit Documentation Feedback 7 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 Terminal Functions (continued) TERMINAL NAME 8 NO. I/O DESCRIPTION HDRV2 25 O Gate drive output for the high-side N-channel MOSFET switch for PWM2. Output is referenced to SW2 and is bootstrapped for enhancement of the high-side switch ILIM 15 I Used to set the cycle-by-cycle current limit threshold. If ILIM threshold is reached, the PWM cycle is terminated and the converter delivers limited current to the output. The relationship between ILIM and the maximum phase current is described in Equation 2 and Equation 3. See the Overcurrent Protection section for more details. LDRV1 29 O Gate drive output for the low-side synchronous rectifier (SR) N-channel MOSFET for PWM1. See Layout Considerations section. LDRV2 27 O Gate drive output for the low-side synchronous rectifier (SR) N-channel MOSFET for PWM2. See Layout Considerations section. OVSET 2 I A resistor divider, on this pin connected to the output voltage sets the overvoltage sense point. PGOOD 16 O Power good indicator of the output voltage. This open-drain output connects to a voltage via an external resistor. When the FB pin voltage is between 0.616 V to 0.784 V (88% to 112% of VREF), the PGOOD output is in a high impedance state. PGND 28 - Power ground reference for the controller lower gate drivers. There should be a high-current return path from the sources of the lower MOSFETs to this pin. RT 17 I Connecting a resistor from this pin to ground sets the oscillator frequency. SS 23 I Provides user programmable soft-start by means of a capacitor connected to the pin. If an undervoltage or over current fault is detected the soft-start capacitor cycles 7 times with no switching before a normal soft-start sequence allowed. SW1 31 I Connect to the switched node on converter 1. Power return for the channel 1 upper gate driver. There should be a high-current return path from the source of the upper MOSFET to this pin. It is also used by the adaptive gate drive circuits to minimize the dead time between upper and lower MOSFET conduction. SW2 26 I Connect to the switched node on converter 2. Power return for the channel 2 upper gate driver. There should be a high-current return path from the source of the upper MOSFET to this pin. It is also used by the adaptive gate drive circuits to minimize the dead time between upper and lower MOSFET conduction. UVLO 22 O A voltage divider from VIN to this pin, set to 1V, determines the input voltage that starts the controller. VDD 12 I Power input for the LDO linear regulator that powers the differential amplifer and the current sense amplifiers. VOUT 3 I Non-inverting input of the differential amplifier. This pin should be connected to VOUT at the point of load. VREF 9 O Output of an internal reference voltage. The load may be up to 100-µA DC. VIN5 30 I Power input for the device. A 1.0-µF ceramic capacitor should be connected from this pin to ground. Submit Documentation Feedback TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 FUNCTIONAL BLOCK DIAGRAM VDD 12 BP5 21 AGND 20 CS1 6 CSRT1 7 VOUT 3 LDO 13 BP8 1 BOOT1 32 HDRV1 31 SW1 30 VIN5 29 LDRV1 28 PGND 24 BOOT2 25 HDRV2 26 SW2 27 LDRV2 16 PGOOD TPS40131RHB U1 + 20 kW U7 + 20 kW 20 kW GSNS 4 U6 20 kW DIFFO 9 + VREF 5 Ramp1 U2 0.7 V U3 PWM1 +EA + U9 ICTLR 10 U12 U5 Anti Cross Conduction U10 + FB 11 SS 23 U4 PWM LOGIC 5 mA COMP 8 BP8 U15 + U18 CS2 19 CSRT2 18 ILIM 15 UVLO 22 EN/SYNC 14 U17 + Ramp2 U14 UV FB VIN5 BP5 RT OVSET 17 2 SS PWM2 U20 U19 OC/UV Detect U22 Power-On Reset U23 Clock U24 Ramp Gen U16 Anti Cross Conduction VIN5 U21 OC Ramp1 OV 100 ns Delay Ramp2 U25 OV Detect UDG-07021 FUNCTIONAL DESCRIPTION The TPS40131 uses programmable fixed-frequency, peak current mode control with forced phase current balancing. Phase current is sensed by using either the DCR (direct current resistance) of the filter inductors or current sense resistors installed in series with output. The first method involves generation of a current signal with an R-C circuit (shown in the applications diagram). The R-C values are selected by matching time constants of the RC circuit and the inductor time constant, R×C = L/DCR. With either current sense method, the current signal is amplified and superimposed on the amplified voltage error signal to provide current mode PWM control. Other features include: a true differential output sense amplifier, programmable current limit, programmable output over-voltage set-point, capacitor set soft-start, power good indicator, programmable input undervoltage lockout (UVLO), user programmable operation frequency for design flexibility, external synchronization capability, programmable pulse-by-pulse overcurrent protection, output undervoltage shutdown and restart. Submit Documentation Feedback 9 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 FUNCTIONAL DESCRIPTION (continued) Startup Sequence Figure 1 shows a typical start up with the VIN5 and BP5 applied to the controller and then the EN/SYNC being enabled. Shut down occurs when the VIN5 is removed VIN5 BP5 EN/SYNC 1.0V 0.7V SS SSWAIT VOUT PGOOD EN_SSWAIT UDG−04031 Figure 1. Startup and Shutdown Sequence Differential Amplifier (U7) The unity gain differential amplifier with high bandwidth allows improved regulation at a user-defined point and eases layout constraints. The output voltage is sensed between the VOUT and GSNS pins. The output voltage programming divider is connected to the output of the amplifier (DIFFO). If there is no need for a differential amplifer, the differential amplifier can be disabled by connecting the GSNS pin to the BP5 pin and leaving VOUT and DIFFO open. The voltage programming divider in this case should be connected directly to the output of the converter. TPS40131 VOUT 20 kΩ 3 20 kΩ GSNS 20 kΩ Differential Amplifier + DIFFO 5 20 kΩ 4 UDG−04081 Figure 2. Differential Amplifier Configuration Because of the resistor configuration of the differential amplifier, the input impedance must be kept very low or there will be error in setting the output voltage. 10 Submit Documentation Feedback TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 FUNCTIONAL DESCRIPTION (continued) Current Sensing and Balancing (U1, U9 and U18) The controller employs peak current mode control scheme, thus naturally provides certain degree of current balancing. With current mode, the level of current feedback should comply with certain guidelines depending on duty factor known as “slope compensation” to avoid the sub-harmonic instability. This requirement can prohibit achieving a higher degree of phase current balance. To avoid the controversy, a separate current loop that forces phase currents to match is added to the proprietary control scheme. This effectively provides high degree of current sharing independent of the controller’s small signal response and is implemented in U9, ICTLR. The useable range of the controller bandwidth is also extended. High bandwidth current amplifiers, U1 and U18 can accept as an input voltage either the voltage drop across dedicated precise current sense resistors, or inductor’s DCR voltage derived by an RC network. The wide range of current sense arrangements ease the cost/complexity constraints and provides superior performance compared to controllers utilizing the low-side MOSFET current sensing. See the Inductor DCR Current Sense section for more information on selecting component values for the R-C network. Hiccup Mode Hiccup mode is a feature that is invoked when certain faults are detected. Hiccup mode allows a time for a fault to clear itself,for instance, a momentary short circuit on the output. The hiccup mode consists of 7 cycles of charging and discharging the soft-start capacitor and then attempting a re-start. If the fault has been cleared, the re-start will cause the output to come up in regulation. If the fault has not been cleared, Hiccup mode is initiated again and another restart will occure after another 7 soft-start cycles. PowerGood The PGOOD pin indicates when the inputs and output are within their specified ranges of operation. Also monitored are the EN/SYNC and SS pins. PGOOD has high impedance when indicating inputs and outputs are within specified limits and is pulled low to indicate an out-of-limits condition. . Soft-Start A capacitor connected to the soft start pin (SS) sets the power-up time. When EN is high and POR is cleared, the calibrated current source starts charging the external soft start capacitor. The PGOOD pin is held low during the start up. The rising voltage across the capacitor serves as a reference for the error amplifier, U12. When the soft-start voltage reaches the level of the reference voltage, the converter’s output reaches the regulation point and further voltage rise of the soft start voltage has no effect on the output. When the soft start voltage reaches 1.0 V, the power good (PGOOD) function is cleared to be reported on the PGOOD pin. Normally the PGOOD pin goes high at this time. Equation 1 is used to calculate the value of the soft-start capacitor. 0.7 C SS t SS + 5 10 *6 (1) Overcurrent Protection The overcurrent function, U19, monitors the output of current sense amplifiers U1 and U18. These currents are converted to voltages and compared to the voltage on the ILIM pin. The relationship between the maximum phase current and the current sense resistance is given in the following equation. In case a threshold of VILIM/2.7 is exceeded the PWM cycle on the associated phase is terminated. The overcurrent threshold, IPH(max), and the voltage to set on the ILIM pin is determined by Equation 2 and Equation 3. V ILIM + 2.7 I PH(max) R CS (2) I PH(max) + ǒV IN * VOUTǓ I OUT ) 2 2 L OUT f SW VOUT V IN (3) where • • • IPH(max) is a maximum value of the phase current allowed IOUT is the total maximum DC output current RCS is a value of the current sense resistor used or the DCR value of the output inductor, LOUT Submit Documentation Feedback 11 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 FUNCTIONAL DESCRIPTION (continued) If the overcurrent condition persists, both phases have PWM cycles terminated by the overcurrent signals. This puts a converter in a constant current mode with the output current programmed by the ILIM voltage. A counter is incremented for each PWM cycle in which an overcurrent event is detected. The counter is reset every 32 PWM cycles. If the counter accumulates a count of 7 before being reset, the converter enters a hiccup mode. The HDRV and LDRV signals are set low during the hiccup mode. The SS capacitor serves as a hiccup timing capacitor controlled by U20, the fault control circuit. The soft-start pin is periodically charged and discharged by U20. After seven hiccup cycles, the controller attempts another soft-start cycle to restore normal operation. If the overload condition persists, the controller returns to the hiccup mode. This condition may continue indefinitely. In such conditions the average current delivered to the load is approximately 1/8 of the set overcurrent value. Overvoltage Protection, Non-Latching The voltage on OVSET is compared with 0.817 V, 16% higher than VREF, in U25 to determine the output overvoltage point. When an overvoltage is detected, the output drivers command the upper MOSFETs off and the lower MOSFETs on. If the overvoltage condition has been cleared, the output comes up and normal operation continues. Turning the lower MOSFET on may cause the output to reach an undervoltage condition and enter the hiccup mode. Using a voltage divider with the same ratio, that sets the output voltage, an output overvoltage is declared when the output rises 16% above nominal. Output Undervoltage Protection If the output voltage, as sensed by U19 on the FB pin becomes less than 0.588 V, the undervoltage protection threshold (84% of VREF), the controller enters the hiccup mode. Programmable Input Undervoltage Lockout Protection A voltage divider that sets 1V on the UVLO pin determines when the controller starts operating. Operation commences when the voltage on the UVLO pin exceeds 1.0 V. If the voltage on the UVLO pin falls to 0.81 V, the controller is turned off and the HDRV and LDRV signals are set low. Power-On Reset (POR) The power-on reset (POR) function, U22, insures the VIN5 and BP5 voltages are within their regulation windows before the controller is allowed to start. Fault Masking Operation If the SS pin voltage is externally limited below the 1-V threshold, the controller does not respond to most faults and the PGOOD output is always low. Only the overcurrent function remains active. The overcurrent protection still continues to terminate PWM cycle every time when the threshold is exceeded but the hiccup mode is not entered. Fault Conditions and MOSFET Control Table 1 shows a summary of the fault conditions and the state of the MOSFETs. Table 1. Fault Condifions 12 FAULT MODE UPPER MOSFET LOWER MOSFET EN/SYNC = LOW OFF OFF FIXED UVLO, VBP5 < 4.25 V OFF OFF Programmable UVLO, < 1.0 V OFF OFF Output undervoltage OFF, Hiccup mode OFF, Hiccup mode Output overvoltage OFF ON Output overcurrent OFF, Hiccup mode OFF, Hiccup mode Submit Documentation Feedback TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 Setting the Switching Frequency The clock frequency is programmed by the value of the timing resistor connected from the RT pin to ground. See Equation 4. R T + 0.8 ƪǒ Ǔ ƫ 103 * 9 36 f PH (4) fPH is a single phase frequency, kHz. The RT resistor value is expressed in kΩ. See Figure 3. 500 RT − Timing Resistance − kΩ 450 400 350 300 250 200 150 100 50 0 0 200 400 600 800 1000 fSW − Phase Switching Frequency − kHz Figure 3. Phase Switching Frequency vs. Timing Resistance EN/SYNC Function The output ripple frequency is twice that of the single-phase frequency. The switching frequency of the controller can be synchronized to an external clock applied to the EN/SYNC pin. The external clock synchronizes the rising edge of HDRV and the falling edge of an external clock source. The switching frequency is one-eighth of the external clock frequency. Setting Overcurrent Protection Setting the overcurrent protection is given in the following equations. Care must be taken when calculating VILIM to include the increase in RCS caused by the output current as it approaches the overcurrent trip point. The DCR (RCS in the equation) of the inductor increases approximately 0.39% per degree Centigrade. V ILIM + 2.7 I PH(max) R CS (5) I PH(max) + ǒV IN * VOUTǓ I OUT ) 2 2 L OUT f SW VOUT V IN (6) where • • • • • • • IPH(max) is a maximum value of the phase current allowed IOUT is the total maximum DC output current LOUT is the output inductor value fSW is the switching frequency VOUT is the output voltage VIN is the input voltage RCS is a value of the current sense resistor used or the DCR value of the output inductor, LOUT Submit Documentation Feedback 13 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 Resistor Divider Calculation for VOUT, ILIM, OVSET and UVLO Use Figure 4 for setting the output voltage, current limit voltage and overvoltage setting voltage. Select RBIAS using Equation 7. With a voltage divider from VREF, select R6 using Equation 8. WIth a voltage from DIFFO select R4 using Equation 9. With a voltage divider from VIN, select R8 using Equation 10. R1 R BIAS + 0.7 ǒV OUT * 0.7Ǔ (7) R6 + R5 R4 + 0.812 R8 + 1.0 VILIM ǒ0.7 * V ILIMǓ (8) R3 ǒVOUT(ov) * 0.812Ǔ (9) R7 ǒVIN * 1.0Ǔ (10) TPS40131RHB OVSET 2 GSNS Differential Amplifier 4 VOUT 3 + DIFFO 5 R2 R3 C1 COMP 8 R1 Error Amplifier FB 11 R4 + +EA RBIAS VIN 10 VREF 9 R5 ILIM 15 R6 UVLO R7 22 + 700 mV R8 UDG−04032 Figure 4. Use for Resistor Divider Calculations INDUCTOR DCR CURRENT SENSE The preferred method for sampling the output current for the TPS40131 is known as the inductor DCR method. This is a lossless approach, as opposed to using a discrete current sense resistor which occupies board area and impacts efficiency as well. The inductor DCR implementation is shown in Figure 5. 14 Submit Documentation Feedback TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 VIN L1 DCR VOUT C1 R1 + VC − To CSRTx To CSx Figure 5. Inductor DCR Current Sense Approach The inductor L1 consists of inductance, L, and resistance, DCR. The time constant of the inductor: L / DCR should equal the R1×C1 time constant. Then choosing a value for C1 (0.1 µF is a good choice) solving for R1 is shown in Equation 11. L1 R1 + DCR C1 (11) The voltage into the current sense amplifier of the controller , VC, is calculated in Equation 12. V OUT V C + ǒVIN * VOUTǓ ) I OC DCR R1 C1 f SW V IN (12) As the DC load increases the majority of the voltage, VC, is determined by (IOC× DCR), where IOC is the per phase DC output current. It is important that at the overcurrent set point that the peak voltage of VC does not exceed 60 mV, the maximum differential input voltage. If the voltage VC exceeds 60 mV, a resistor, R2,can be added in parallel with C1 as shown in Figure 6. Adding R2 reduces the equivalent inductor DCR by the ratio shown in Equation 14 VIN L1 DCR VOUT C1 R1 R2 + VC − To CSRTx To CSx Figure 6. Using Resistor R2 to Reduce the Current Sense Amplifier Voltage The parallel combination of R1 and R2 is shown in Equation 13. L1 R1 ø R2 + DCR C1 (13) The ratio shown in Equation 14 provides the required voltage attenuation. R2 R1 ) R2 (14) Submit Documentation Feedback 15 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 APPLICATION INFORMATION LAYOUT CONSIDERATIONS Power Stage A synchronous BUCK power stage has two primary current loops. One is the input current loop that carries high AC discontinuous current . The other is the output current loop that carries high DC continuous current. The input current loop includes capacitors and the ground path generally good practice to place MOSFET and the source of the MOSFETs. the input capacitors, the main switching MOSFET, the inductor, the output back to the input capacitors. To keep this loop as small as possible, it is some ceramic capacitance directly between the drain of the main switching synchronous rectifier (SR) through a power ground plane directly under the The output current loop includes the SR MOSFET, the inductor, the output capacitors, and the ground return between the output capacitors and the source of the SR MOSFET. As with the input current loop, the ground return between the output capacitor ground and the source of the SR MOSFET should be routed under the inductor and SR MOSFET to minimize the power loop area. The SW node area should be as small as possible to reduce the parasitic capacitance and minimize the radiated emissions. The gate drive loop impedance (HDRV-gate-source-SW and LDRV-gate-source- GND) should be kept to as low as possible. The HDRV and LDRV connections should widen to 20 mils as soon as possible out from the device's pin. Device Peripheral The TPS40131 provides separate signal ground (GND) and power ground (PGND) pins. It is required to separate properly the circuit grounds. The return path for the pins associated with the power stage should be through PGND. The other pins especially for those sensitive pins such as FB, RT and ILIM should be through the low noise GND. The GND and PGND plane are suggested to be connected at the output capacitor with single 20 mil trace. A minimum 0.1-µF ceramic capacitor must be placed as close to the VDD pin and GND as possible with at least 15-mil wide trace from the bypass capacitor to the GND. A 1-µF ceramic capacitor should be placed as close to VIN5 pin and GND as possible. BP5 is the filtered input from the VIN5 pin. A 10 Ω resistor should be connected between VIN5 and BP5 and a 1-µF ceramic capacitor should be connected from BP5 to GND. Both components should be as close to BP5 pin as possible. When DCR sensing method is applied, the sensing resistor is placed close to the SW node. It is connected to the inductor with Kelvin connection. The sensing traces from the power stage to the device should be away from the switching components. The sensing capacitor should be placed very close to the CS and CSRT pins. The frequency setting resistor should be placed as close to RT pin and GND as possible. The VOUT and GSNS pins should be directly connected to the point of load where the voltage regulation is required. A parallel pair of 10-mil traces connects the regulated voltage back to the chip. They should be away from the switching components. The PowerPAD should be electrically connected to GND. Figure 7 shows the device peripheral schematic and Figure 8 shows the suggested layout. 16 Submit Documentation Feedback TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 APPLICATION INFORMATION (continued) R2 C4 R3 C6 C7 R5 C5 R10 R7 R8 D1 R9 C11 R14 R15 C20 C22 C25 9 10 11 12 13 14 R16 15 16 COMP CSRT1 CS1 DIFFO GSNS VOUT OVSET BOOT1 R6 VREF +EA FB VDD BP8 EN/SYNC ILIM PGOOD U1 RT CSRT2 CS2 AGND BP5 UVLO SS BOOT2 C9 8 7 6 5 4 3 2 1 R11 17 18 19 20 21 22 23 24 R17 C10 PwPd HDRV1 SW1 VIN5 LDRV1 PGND LDRV2 SW2 HDRV2 33 32 31 30 29 28 27 26 25 C21 R18 C26 R20 R19 C31 C27 D2 R22 C30 C32 R25 C33 Figure 7. TPS40131 Peripheral Schematic AGND AGND CSRT1 FB AGND VOUT GSNS CS1 BOOT1 HDRV1 FB VIN5 AGND LDRV1 12VIN PGND ILIM LDRV2 HDRV2 AGND BOOT2 AGND AGND CSRT1 CS2 BP5 12VIN AGND Figure 8. TPS40131 Recommended Layout for Peripheral Components Submit Documentation Feedback 17 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 APPLICATION INFORMATION (continued) PowerPAD™ Layout The PowerPAD™ package provides low thermal impedance for heat removal from the device. The PowerPAD™ derives its name and low thermal impedance from the large bonding pad on the bottom of the device. The circuit board must have an area of solder-tinned-copper underneath the package. The dimensions of this area depend on the size of the PowerPAD™ package. Thermal vias connect this area to internal or external copper planes and should have a drill diameter sufficiently small so that the via hole is effectively plugged when the barrel of the via is plated with copper. This plug is needed to prevent wicking the solder away from the interface between the package body and the solder-tinned area under the device during solder reflow. Drill diameters of 0.33 mm (13 mils) works well when 1-oz. copper is plated at the surface of the board while simultaneously plating the barrel of the via. If the thermal vias are not plugged when the copper plating is performed, then a solder mask material should be used to cap the vias with a diameter equal to the via diameter plus 0.1 mm minimum. This capping prevents the solder from being wicked through the thermal vias and potentially creating a solder void under the package. Refer to PowerPAD™ Thermally Enhanced Package (SLMA002) for more information on the PowerPAD™ package. 18 Submit Documentation Feedback TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 DESIGN EXAMPLE Two Phase Single Output Configuration from 12 V to 1.5 V DC/DC Converter Using a TPS40131 The following example illustrates the design process and component selection for a two phase single output synchronous buck converter using TPS40131. The design goal parameters are given in the table below. Design Goal Parameters PARAMETER TEST CONDITIONS VIN Input voltage VOUT Output voltage VRIPPLE Output ripple IOUT Output current fSW Switching frequency MIN TYP MAX 10.8 12.0 13.2 1.5 IOUT = 40 A 30 UNIT V mV 40 A 350 kHz Setp 1: Inductor Selection The inductor is determined by the desired ripple current. The required inductor is calculated using Equation 15. L= VIN(max) - VOUT IRIPPLE ´ VOUT 1 ´ VIN(max) fSW (15) Typically the peak-to-peak inductor current IRIPPLE is selected to be around 20% of the rated output current. In this design, IRIPPLE is targeted at 23% of IPHASE. The calculated inductor is 0.815 µH and in practical a 0.82-µH, 30-A inductor with 2-mΩ DCR from Vishay is selected. The real inductor ripple current is 4.63 A. Step 2: Output Capacitor Slection The output capacitor is typically selected by the output load transient response requirement. Equation 16 estimates the minimum capacitor to reach the undervoltage requirement with load step up. Equation 17 estimates the minimum capacitor for overvoltage requirement with load step down. When VIN(min) < 2×VOUT, the minimum output capacitance can be calculated using Equation 16. Otherwise, Equation 17 is used. COUT(min) 2 1 ´ ITRAN(max) ´ L 2 = VIN(min) - VOUT ´ VUNDER ( ) ( ) 2 1 ´ ITRAN(max) ´ L COUT(min) = 2 (VOUT ´ VOVER ) ( (16) ) (17) In this design, VIN(min) is much larger than 2 × VOUT, so Equation 17 is used to determine the minimum capacitance. Based on a 15-A load transient with a maximum of 80-mV deviation, a minimum 1-mF output capacitor is required. In the design, six 180-µF, 6.3-V SP capacitors are selected to meet this requirement. Each capacitor has an ESR of 5 mΩ. Due to the interleaving of channels, the total output ripple current is smaller than the ripple current from a single phase. The ripple cancellation factor is expressed in Equation 18. DIOUT (D) = 1- 2 ´ D ´ 2 - 2 ´ D 1- 2 ´ D + 1 (18) where • D is the duty cycle for a single phase The maximum output ripple current is calculated in Equation 19. Submit Documentation Feedback 19 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 IRIPPLE = VOUT ´ DIOUT (D) = 4.04 A L ´ fsw (19) With 1.08-mF output capacitance, the ripple voltage at the capacitor is calculated to be 1.34 mV. In the specification, the output ripple voltage should be less than 30 mV, so based on the following equation, the required maximum ESR is 7.1 mΩ. The selected capacitors can meet this requirement. æ ö IRIPPLE VRIPPLE(TotOUT) - ç ÷ VRIPPLE(TotOUT) - VRIPPLE(COUT) è 8 ´ COUT ´ fSW ø = ESRCo = IRIPPLE IRIPPLE (20) Step 3: Input Capacitor Selection The input voltage ripple depends on input capacitance and ESR. The minimum capacitor and the maximum ESR can be estimated using Equation 21. CIN(min) = ESR Cin = IOUT ´ VOUT VRIPPLE(CIN) ´ VIN ´ fSW (21) VRIPPLE(CinESR) IOUT + ((12 )´ IRIPPLE ) (22) For this design, assume VRIPPLE(Cin) is 60 mV and VRIPPLE(CinESR) is 30 mV, so the calculated minimum capacitance is 120-µF and the maximum ESR is 1.35 mΩ. Choosing six 22-µF, 16V, 2-mΩ ESR ceramic capacitors meets this requirement. Another important thing for the input capacitor is the RMS ripple current rating. Due to the interleaving of multi-phase, the input RMS current is reduced. The input ripple current RMS value over load current is calculated using Equation 23. DIIN (D) = D ´ (0.5 - D) ´ IOUT (23) So in this design, the maximum input ripple RMS current is calculated to be 8.96 A with the minimum input voltage. It is about 35% reduction compared with a 40-A single-phase converter design. Each selected ceramic capacitor has a RMS current rating of 4.3 A, so it is sufficient to meet this requirement. Step 4: MOSFET Selection The MOSFET selection determines the converter efficiency. In this design, the duty cycle is very small so that the high-side MOSFET is dominated with switching losses and the low-side MOSFET is dominated with conduction loss. To optimize the efficiency, choose smaller gate charge for the high-side MOSFET and smaller RDS(on) for the low-side MOSFET. Renesas HAT2167H and HAT2164H are selected as the high-side and low-side MOSFET respectively. In the following calculations, only the losses for one phase are shown. The power losses in the high-side MOSFET is calculated with the following equations. The RMS current in the high-side MOSFET is shown in Equation 24. 2 æ 2 (IRIPPLE ) ISWrms = D ´ ç (IOUT ) + ç 12 è ö ÷ = 7.08 ÷ ø (24) The RDS(on)(sw) is 9.3 mΩ when the MOSFET gate voltage is 4.5 V. The conduction loss is shown in Equation 25. 2 PSWcond = (ISWrms ) ´ RDS(on)(sw) = 0.467 W The switching loss is shown in Equation 26. 20 Submit Documentation Feedback (25) TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 I ´ VIN ´ fSW ´ RDRV ´ (Qgdsw + Qgssw ) PSW(sw) = PK = 0.438 W Vgtdrv (26) The calculated total loss is the high-side MOSFET is shown in Equation 27. PSW(tot) = Psw (cond) + PSW(SW ) = 0.935 W (27) The power losses in the low-side SR MOSFET is calculated using <CR>. The RMS current in the low-side MOSFET is calculated using Equation 28. 2 æ 2 (IRIPPLE ) ISRrms = (1 - D) ´ ç (IOUT ) + ç 12 è ö ÷ = 18.7A ÷ ø (28) The RDS(on)(sr) of each HAT2164H is 4.4mΩ when the gate voltage is 4.5 V. Two HAT2164H are used in parallel to reduce the conduction loss. The conduction loss in the low-side MOSFETs is shown in Equation 29. 2 æ RDS(on)(sr) PSR(cond) = (ISRrms ) ´ ç ç 2 è ö ÷÷ = 0.77 W ø (29) The total power loss in the body diode is shown in Equation 30. PDIODE = 2 ´ IOUT ´ tD ´ Vf ´ fSW = 0.49 W (30) Therefore, the calculated total loss in the SR MOSFETs is as described in Equation 31. PSR(tot) = PSR(cond) + PDIODE = 1.26 W (31) Step 5: Peripheral Component Design RT (Pin 17) Switching Frequency Setting æ 36 ´ (10 )3 ö - 9 ÷ = 75kW RT = 0.8 ´ ç ç ÷ fSW è ø (32) In Equation 32, the phase switching frequency and it is 350 kHz here. SS (Pin 23) Soft-Start To obtain a 3-ms soft-start time, calculate CSS which is connected between SS and GND. CSS = -3 tSS 3 140 ´ (10 ) = 3 ´ (10 ) 3 = 21nF 140 ´ (10 ) (33) FB (Pin 11) Output Voltage Setting Select the top resistor to be 10 kΩ, calculate the bottom resistor RBAIS using Equation 34. æ 10 ´ (10 )3 ö ÷ = 8.75kW RBIAS = 0.7 ´ ç ç (VOUT - 0.7 ) ÷ è ø (34) (Pin 6, Pin 7, Pin 18 and Pin 19) Current Sensing Network Design In this design, the lossless inductor DCR sensing is applied. Choose the sense capacitor a value for 0.1 µF, and calculate the sense resistor R with Equation 35 and Equation 36. Submit Documentation Feedback 21 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 R= L = 6kW DCR ´ C (35) The simplified equation to determine if the design produces sub-harmonics is shown in Equation 35. VIN ´ 6 L > DCR 2 ´ VRAMP ´ fSW (36) This condition is satisfied in this design. Both CSRT1 and CSRT2 are recommended to connect to GND with a 1-µF capacitor for the purpose of eliminating noise. ILIM (Pin 15) Current Limit The overcurrent protection level is calculated with equations below. IPK = IOC(dc ) + (VIN - VOUT )´ VOUT 2 ´ L ´ fSW ´ VIN = 27.32 A (37) VILIM = 2.7 ´ IPK ´ DCR = 148mV (38) IOC(dc) is the DC overcurrent protection level for each phase. In this design, it is 25 A per phase. DCR is 2 mΩ. A resistor divider is connected from VREF (pin 9) to GND to provide an accurate VILIM voltage. Choose a value of 10 kΩ for the top resistor, and then the bottom resistor is calculated using Equation 39. æ 10 ´ (10 )3 RB = VLIM ´ ç ç VREF - VLIM è ö ÷ = 2.7 k W ÷ ø (39) OVSET (Pin 2) Output Voltage Setting A resistor divider is connected from VOUT to GND to set the overvoltage protection threshold. In this design, the resistor divider is the same as the output voltage setting resistor divider, so the OVSET level is 16% of the set output voltage. UVLO (Pin 22) Undervoltage Lockout UVLO is connected to the input voltage and GND with a resistor divider. The resistor connected to VIN is chosen to be 10 kΩ and the resistor connected to GND is selected to be a value of 2.49 kΩ. When the input voltage is higher than 5 V, the chip is enabled. PGOOD (Pin 16) Powergood PGOOD is connected to BP5 with a 10-kΩ resistor. VOUT, GSNS and DIFFO (Pin 3) (Pin 4) (Pin 5) VOUT and GSNS are connected to the remote sensing output connector. DIFFO is connected to the feedback resistor divider. If the differential amplifier is not used, VOUT and GSNS should be grounded, and DIFFO is left open. 22 Submit Documentation Feedback TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 BOOT1, BOOT2, SW1, SW2 (Pin 1) (Pin 24) (Pin 31) (Pin 26) A bootstrap capacitor is connected between the BOOT1 and SW1 pin or between BOOT2 and SW2 pin. The bootstrap capacitor depends on the total gate charge of the high-side MOSFET and the amount of droop allowed on the bootstrap capacitor. CBOOT = Qg = 85nF DV (40) where • • Qg is 17nC ∆ V is 0.2 V For this application, a 0.1-µF capacitor is selected. To reduce the turn on speed of the high-side MOSFET and control the ringing, a 2-Ω resistor is placed in series with the BOOT pin. EN/SYNC (Pin 14) Enable and Synchronization This pin is either tied to BP5 to enable the chip or connected to an external clock. VREF EA+ (Pin 9) (Pin 10) Voltage Reference and Error Amplifier VREF and EA+ are directly connected together. A 0.1-µF decoupling capacitor is recommended. VDD, VIN5, BP5, BP8, AGND, PGND, PwPd (Pin 12) (Pin 30) (Pin 21) (Pin 13) (Pin 20) (Pin 28) (Pin 33) VDD is directly connected to VIN and a 0.1-µF decoupling capacitor is recommended. VIN5 is connected to external +5 V and a 100-µF bulk capacitor and a 1-µF decoupling capacitor are recommended. BP5 is filtered from VIN5. A 10-Ω resistor and a 0.1-µF capacitor are recommended for the low pass filter. BP8 is decoupled with a 0.1-µF capacitor to GND. A GND and PwPd are tied to analog GND and PGND is tied to power GND. Feedback Compensator Design Peak current mode control method is employed in the controller. A small signal model is developed from the COMP signal to the output. GVC(s) = (s ´ COUT ´ ESR + 1) ´ ROUT 1 1 ´ ´ DCR ´ Ac s ´ ts + 1 s ´ COUT ´ ROUT + 1 (41) The time constant, τS, is defined by Equation 42. ts = T æ æ æ VRAMP ö æ VIN - VOUT ö öö +ç ´ DCR ´ Ac ÷ ÷ ç çç ÷ ÷ L ø ç è T ø è ø÷ lnç è ÷ æ VRAMP ö æ VOUT ö ç ÷ -ç ´ DCR ´ Ac ÷ ç ÷ ç ÷ è T ø è L ø è ø (42) The low frequency pole is calculated in Equation 43. fVCP1 = 1 = 3.84kHz 2 ´ p ´ COUT ´ ROUT (43) Another pole from control to output is calculated in Equation 44. fVCP2 = 1 = 46.3kHz 2 ´ p ´ tS (44) Submit Documentation Feedback 23 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 The ESR zero is calculated in Equation 45. fESR = 1 = 176.8kHz 2 ´ p ´ COUT ´ ESR (45) In this design, a Type III compensator is employed to compensate the loop. R1 R3 VREF C1 + C3 R2 C2 Figure 9. Type III Compensator The compensator transfer function is shown in Equation 46. æ 1 GC(s) = ç ç R1´ (C2 + C3 ) è ( ( ) ö s ´ (R1 + R3 )´ C1 + 1 ´ (s ´ R2 ´ C2 + 1) ÷´ ÷ æ C2 ´ C3 ö ö ø s ´ (s ´ R3 ´ C1 + 1)´ ç s ´ R2 ´ çæ + 1÷ C2 + C3 ÷ø ø è è ) (46) The loop gain transfer function is shown in Equation 47. TV(s) = GC(s) ´ GVC(s) (47) Assume the desired crossover frequency is 20 kHz. Place one zero at fVCP1 and another zero at fVCP2, then place one pole at fESRand another pole at fSW. The compensator gain is then calculated to achieve the desired bandwidth. In this design, the compensator gain, pole and zero are selected using the following equations: fP1 = fP2 = fZ1 = fZ2 = 1 = fESR 2 ´ p ´ R3 ´ C1 (48) 1 = fSW æ C2 ´ C3 ö 2 ´ p ´ R2 ´ ç ÷ è C2 + C3 ø (49) 1 = fVCP1 2 ´ p ´ R2 ´ C2 (50) 1 = fVCP2 2 ´ p ´ (R1 + R3 ) ´ C1 (51) TV ( j ´ 2 ´ p ´ fC ) = 1 (52) 4 From Equation 52 the compensator gain is solved as 2.09×10 . æ ö 1 4 A CM = ç ÷ = 2.09 ´ (10 ) ç R1´ (C2 + C3 ) ÷ è ø Set R1 equal to 10 kΩ, and then calculate all the other components. 24 Submit Documentation Feedback (53) TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 • • • • • R2 R3 C1 C2 C3 = = = = = 8.4 kΩ 3.5 kΩ 260 pF 4.7 nF 50 pF In the real lab practice, the final components are selected as following to increase the phase margin and reduce PWM jitter. • R1 = 10 kΩ • R2 = 5 kΩ • R3 = 3 kΩ • C1 = 470 pF • C2 = 4.7 nF • C3 = 47 pF Submit Documentation Feedback 25 Submit Documentation Feedback 2.7K 3K 0.1uF 0.1uF 0.1uF 470pF 10K 0.1uF 10K 8.75K 9 10 11 12 13 14 15 16 47pF 10K open 0.1uF 0.1uF 22nF 2.49K 10K 2 0.1uF 10 33 32 31 30 1uF 29 28 27 26 25 100uF + 22uF BAT54HT1 0.1uF 0.1uF BAT54HT1 1uF PwPd HDRV1 SW1 VIN5 LDRV1 PGND LDRV2 SW2 HDRV2 2 20 8.75K VREF +EA FB VDD TPS40131RHB BP8 EN/SYNC ILIM PGOOD 4.7nF 1uF 75k 10K 5.1 5K 8 7 6 5 4 3 2 1 COMP CSRT1 CS1 DIFFO GSNS VOUT OVSET BOOT1 RT CSRT2 CS2 AGND BP5 UVLO SS BOOT2 17 18 19 20 21 22 23 24 26 0.1uF open 0.1uF 6K 6K 1 0.82uH 3.3n 3.3n 1 0.82uH + 180u 10 10 47u TPS40131 SLVS635 – FEBRUARY 2007 www.ti.com Design Example Summary Figure 10 shows the schematic summarizes the above design. Figure 10. Converting from 12 V to 1.5 V Output for IOUT = 40 A TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 EFFICIENCY vs LOAD CURRENT OUTPUT VOLTAGE vs LOAD CURRENT 1.510 100 90 VOUT - Output Voltage - V 80 h - Efficiency - % 70 60 50 40 30 VIN 20 1.505 VIN = 10.8 V 1.500 VIN = 13.2 V 1.495 VIN 10.8 V 12.0 V 13.2 V 10.8 V 12.0 V 13.2 V 10 1.490 0 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 IOUT - Load Current - A IOUT - Load Current - A Figure 11. Efficiency vs. Load Figure 12. Load Regulation VOUT (50 mV / div) IOUT (10 A / div) T - Time - 200 ms/div Figure 13. 0 A to 15 A Load Step Submit Documentation Feedback 27 Submit Documentation Feedback TL431 1K 3K 100K 9 10 11 12 13 14 15 16 0.1uF 20 open 0.1uF 0.1uF 22nF 2.49K 10K 2 0.1uF 10 33 32 31 30 1uF 29 28 27 26 25 100uF + 22uF BAT54HT1 0.1uF 0.1uF BAT54HT1 1uF PwPd HDRV1 SW1 VIN5 LDRV 1 PGND LDRV 2 SW2 HDRV2 2 1.5K 10K VREF +EA FB VDD TPS40131RHB BP8 EN/SYNC ILIM PGOOD 1uF 75k 10K 5.1 1N5819 0.1uF 10K 1.5K 2N7002 0.1uF 0.1uF 90K 2.7K 0.1uF 470pF 10K 47pF 4.7nF 8 7 6 5 4 3 2 1 COMP CSRT1 CS1 DIFFO GSNS VOUT OVSET BOOT1 RT CSRT2 CS2 AGND BP5 UVLO SS BOOT2 28 17 18 19 20 21 22 23 24 5K open 0.1uF 6K 6K 1 2.65uH 3.3n 3.3n 1 2.65uH + 180u 10 10 47u TPS40131 SLVS635 – FEBRUARY 2007 www.ti.com 12 V to 5 V Converter Application The following schematic shows an application that converts 12 V to 5 V. The 5-V output is used to power up the device after start up. Figure 14. Converting from 12 V to 5 V Output for IOUT = 20 A TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 EFFICIENCY vs LOAD CURRENT OUTPUT VOLTAGE vs LOAD CURRENT 5.400 100 VIN = 12 V 90 5.395 VOUT - Output Voltage - V 80 h - Efficiency - % 70 60 50 40 30 20 5.390 5.385 5.380 5.375 10 VIN = 12 V 5.370 0 0 0 4 8 12 16 4 8 12 16 20 20 IOUT - Load Current - A IOUT - Load Current - A Figure 15. Efficiency vs. Load Current Submit Documentation Feedback Figure 16. Load Regulation 29 Submit Documentation Feedback 2.7K 0.1uF 0.1uF 0.1uF 470pF 10K 3K 0.1uF 10K 8.75K 9 10 11 12 13 14 15 16 47pF open 0.1uF 0.1uF 22nF 3K 10K 2 0.1uF 10 33 32 31 30 1uF 29 28 27 26 25 100uF + 22uF BAT54HT1 0.1uF 0.1uF BAT54HT1 1uF PwPd HDRV1 SW1 VIN5 LDRV1 PGND LDRV2 SW2 HDRV2 2 20 8.75K 10K VREF +EA FB VDD TPS40131RHB BP8 EN/SYNC ILIM PGOOD 4.7nF 1uF 75k 10K 5.1 5K 8 7 6 5 4 3 2 1 COMP CSRT1 CS1 DIFFO GSNS VOUT OVSET BOOT1 RT CSRT2 CS2 AGND BP5 UVLO SS BOOT2 17 18 19 20 21 22 23 24 30 0.1uF open 0.1uF 6K 6K 1 0.82uH 3.3n 3.3n 1 0.82uH + 180u 10 10 47u TPS40131 SLVS635 – FEBRUARY 2007 www.ti.com 5 V to 1.5 V Converter Application The following schematic shows an application that converts 5 V to 1.5 V. Figure 17. Converting from 5 V to 1.5 V Output for IOUT = 30 A TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 EFFICIENCY vs LOAD CURRENT OUTPUT VOLTAGE vs LOAD CURRENT 1.520 100 VIN = 5 V 90 1.518 VOUT - Output Voltage - V 80 h - Efficiency - % 70 60 50 40 30 1.516 1.514 1.512 20 10 VIN = 5 V 1.510 0 0 5 10 15 20 25 30 0 5 10 15 20 25 30 IOUT - Load Current - A IOUT - Load Current - A Figure 18. Efficiency vs. Load Current Submit Documentation Feedback Figure 19. Load Regulation 31 TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 Table 2. Definitions SYMBOL DESCRIPTION VIN(min) Minimum Operating Input Voltage VIN(max) Maximum Operating Input Voltage VOUT Output Voltage IRIPPLE Inductor Peak-Peak Ripple Current ITRAN(max) Maximum Load Transient VUNDER Output Voltage Undershot VOVER Output Voltage Overshot VRIPPLE(totOUT) Total Output Ripple VRIPPLE(Cout) Output Voltage Ripple Due to Output Capacitance VRIPPLE(Cin) Input Voltage Ripple Due to Input Capacitance VRIPPLE(CinESR) Input Voltage Ripple Due to the ESR of Input Capacitance PSW(cond) High-Side MOSFET Conduction Loss ISW(rms) RMS Current in the High-Side MOSFET RDS(on)(sw) "ON" Drain-Source Resistance of the High-Side MOSFET PSW(sw) High-Side MOSFET Switching Loss IPK Peak Current Through the High-Side MOSFET RDRV Driver Resistance of the High-Side MOSFET Qgd(SW) Gate to Drain Charge of the High-Side MOSFET Qgs(SW) Gate to Source Charge of the High-Side MOSFET VqSW Gate Drive Voltage of the High-Side MOSFET PSW(gate) Gate Drive Loss of the High-Side MOSFET Qg(SW) Gate Charge of the High-Side MOSFET PSW(tot) Total Losses of the High-Side MOSFET PSR(cond) Low-Side MOSFET Conduction Loss ISRrms RMS Current in the Low-Side MOSFET RDS(on)(sr) "ON" Drain-Source Resistance of the Low-Side MOSFET PSR(gate) Gate Drive Loss of the Low-Side MOSFET QgSR Gate Charge of the Low-Side MOSFET VqSW Gate Drive Voltage of the Low-Side MOSFET PDIODE Power Loss in the Diode tD Dead Time Between the Conduction of High and Low-Side MOSFET VF Forward Voltage Drop of the Body Diode of the Low-Side MOSFET PSR(tot) Total Losses of the Low-Side MOSFET DCR Inductor DC Resistance AC The Gain of the Current Sensing Amplifier, typically it is 13 ROUT Output Load Resistance VRAMP Ramp Amplitude, typically it is 0.5V T Switching Period GVC(s) Control to Output Transfer Function GC(s) Compensator Transfer Function TV(s) Loop Gain Transfer Function ACM Gain of the Compensator fP1, fP2 Pole Frequency of the Compensator fZ1, fZ2 Zero Frequency of the Compensator 32 Submit Documentation Feedback TPS40131 www.ti.com SLVS635 – FEBRUARY 2007 Submit Documentation Feedback 33 PACKAGE OPTION ADDENDUM www.ti.com 22-Mar-2007 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TPS40131RHBR ACTIVE QFN RHB 32 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS40131RHBT ACTIVE QFN RHB 32 250 CU NIPDAU Level-2-260C-1 YEAR Green (RoHS & no Sb/Br) Lead/Ball Finish MSL Peak Temp (3) (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. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 1 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 Low Power Wireless www.ti.com/lpw Telephony www.ti.com/telephony Mailing Address: Video & Imaging www.ti.com/video Wireless www.ti.com/wireless Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright © 2007, Texas Instruments Incorporated PACKAGE OPTION ADDENDUM www.ti.com 7-May-2007 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TPS40131RHBR ACTIVE QFN RHB 32 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS40131RHBRG4 ACTIVE QFN RHB 32 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS40131RHBT ACTIVE QFN RHB 32 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS40131RHBTG4 ACTIVE QFN RHB 32 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Lead/Ball Finish MSL Peak Temp (3) (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. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 17-May-2007 TAPE AND REEL INFORMATION Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com Device 17-May-2007 Package Pins Site Reel Diameter (mm) Reel Width (mm) A0 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant TPS40131RHBR RHB 32 MLA 330 12 5.3 5.3 1.5 8 12 PKGORN T2TR-MS P TPS40131RHBT RHB 32 MLA 180 12 5.3 5.3 1.5 8 12 PKGORN T2TR-MS P TAPE AND REEL BOX INFORMATION Device Package Pins Site Length (mm) Width (mm) TPS40131RHBR RHB 32 MLA 346.0 346.0 29.0 TPS40131RHBT RHB 32 MLA 190.0 212.7 31.75 Pack Materials-Page 2 Height (mm) PACKAGE MATERIALS INFORMATION www.ti.com 17-May-2007 Pack Materials-Page 3 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. TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing such use. 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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 RFID www.ti-rfid.com Telephony www.ti.com/telephony Low Power Wireless www.ti.com/lpw Video & Imaging www.ti.com/video Wireless www.ti.com/wireless Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright © 2007, Texas Instruments Incorporated