TPS51220 www.ti.com SLVS785 – OCTOBER 2007 Fixed Frequency, 99% Duty Cycle Peak Current Mode Notebook System Power Controller FEATURES 1 • Input Voltage Range: 4.5V to 28V • Output Voltage Range: 1V to 12V • Selectable Light Load Operation (Continuous / Auto Skip / Out-Of-Audio™ Skip) • Programmable Droop Compensation • Voltage Servo Adjustable Soft Start • 200kHz to 1MHz Fixed Frequency PWM • Selectable Current/D-CAP™ Mode Architecture • 180° Phase Shift Between Channels • Resistor or Inductor DCR Current Sensing • • 2 • • • • Powergood Output for Each Channel OCL/OVP/UVP/UVLO Protections (OVP Disable Option) Thermal Shutdown (Non-Latch) Output Discharge Function (Disable Option) Integrated Boot Strap MOSFET Switch QFN32 (RHB) APPLICATIONS • • Notebook Computer System and I/O Bus Point of Load in LCD TV, MFP DESCRIPTION The TPS51220 is a dual synchronous buck regulator controller with 2 LDOs. It is optimized for 5V/3.3V system controller, enabling designers to cost effectively complete 2-cells to 4-cells notebook system power supply. The TPS51220 supports high efficiency, fast transient response and 99% duty cycle operation. It supports supply input voltages ranging from 4.5V to 28V, and output voltages from 1V to 12V. Two types of control schemes can be chosen depending on the application. Peak current mode supports stability operation with lower ESR capacitor and output accuracy. The D-CAP mode supports fast transient response. The high duty (99%) operation and the wide input/output voltage range supports flexible design for small mobile PCs and a wide variety of other applications. The fixed frequency can be adjusted from 200kHz to 1MHz by a resistor, and each channel runs 180° out of phase. The TPS51220 can also synchronize to the external clock, and the interleaving ratio can be adjusted by its duty. The TPS51220 is available in the 32 pin 5x5 QFN package and is specified from –40°C to 85°C. TYPICAL APPLICATION CIRCUIT VBAT VBAT C14 PGND C24 Q12 PGND VO1 2 V5SW 3 RF 4 EN1 5 PGOOD1 6 SKIPSEL1 7 CSP1 30 29 28 27 26 DRVL1 GND DRVL2 VBST2 DRVH1 L2 C21 Q22 VREG5 31 SW1 1 32 VBST1 PGND C22 PGND GND PGND C11 PGND Q21 C01 PGND DRVH2 PGND 24 VIN 23 VBAT R01 VREG3 22 C03 GND EN1 PGOOD1 SKIPSEL1 PGOOD2 VO1 12 13 14 15 CSN2 17 16 VREG5 GND R23 R13 C02 R21 VO2 R12 GND C23 VFB2 11 COMP2 10 TRIP VREF2 9 EN CSN1 FUNC GND GND SKIPSEL2 R24 COMP1 8 R11 PGOOD2 20 SKIPSEL2 19 CSP2 18 VFB1 C13 VREG3 3.3V/10mA EN2 PowerPAD R14 EN EN2 21 TPS51220RHB (QFN32) VO2 3.3 V 25 SW2 L1 VO1 5.0 V VREG5 5V/100mA Q11 C12 R22 GND GND 1 2 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. Out-Of-Audio, D-CAP, PowerPAD are trademarks of Texas Instruments. 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 TPS51220 www.ti.com SLVS785 – OCTOBER 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. FUNCTIONAL BLOCK DIAGRAM VIN EN V5SW + 4.7V/ 4.5V + 1.25V + + VREG5 4.7V/ 4.5V VREG3 GND V5OK + 4.2V/ 3.8V Ready GND + THOK 150/ 140 Deg-C VREF2 1.25V GND GND CLK2 OSC RF CLK1 GND 1V +5%/ 10% + PGOOD1 Delay + 1V -30% 1V - 5%/ 10% + GND UVP CLK1 Ready + FUNC Fault2 OVP SDN2 1V +15% Fault1 COMP1 Ramp Comp CUR VFB1 SDN1 + + PWM VREG5 1V + Enable/ Soft-start + D-CAP VFB-AMP EN1 VREF2 VBST1 Ramp Comp + Skip DRVH1 CS-AMP CSN1 SW1 + OCP + CSP1 Control Logic XCON VREG5 100mV DRVL1 TRIP Discharge Control GND GND 100mV VREF2 N-OCP + GND OOA Ctrl GND SKIPSEL1 Channel-1 Switcher shown 2 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 ABSOLUTE MAXIMUM RATINGS (1) over operating free-air temperature range (unless otherwise noted) VALUE UNIT VIN –0.3 to 30 V VBST1, VBST2 –0.3 to 35 V –0.3 to 7 V –2 to 30 V CSP1, CSP2, CSN1, CSN2 –1 to 13.5 V EN, EN1, EN2, VFB1, VFB2, TRIP, SKIPSEL1, SKIPSEL2, FUNC –0.3 to 7 V V5SW –0.3 to 7 V –7 to 7 V DRVH1, DRVH2 –2 to 35 V DRVH1, DRVH2 (3) –0.3 to 7 V DRVL1, DRVL2, COMP1, COMP2, VREG5, RF, VREF2, PGOOD1, PGOOD2 –0.3 to 7 V VBST1, VBST2 VI Input voltage range (3) SW1, SW2 (2) V5SW (to VREG5) (4) VO Output voltage range (2) –0.3 to 3.6 V TJ Operating junction temperature range –40 to 125 °C Tstg Storage temperature –55 to 150 °C VREG3 (1) (2) (3) (4) 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. All voltage values are with respect to the network ground terminal unless otherwise noted. Voltage values are with respect to the corresponding SW terminal. When EN is high and V5SW is grounded, or voltage is applied to V5SW when EN is low. DISSIPATION RATINGS (2 oz. Trace and Copper Pad with Solder) PACKAGE TA < 25°C POWER RATING DERATING FACTOR ABOVE TA = 25°C TA = 85°C POWER RATING 32 pin RHB 2.2 W 23 mW/°C 0.9 W RECOMMENDED OPERATING CONDITIONS MIN VSS VI VO TA Supply voltage I/O voltage VIN TYP MAX 4.5 28 V5SW –0.8 6 VBST1, VBST2, DRVH1, DRVH2 –0.1 33 DRVH1, DRVH2 (wrt SW1, 2) –0.1 6 SW1, SW2 –1.6 28 CSP1, CSP2, CSN1, CSN2 –0.8 13 EN, EN1, EN2, VFB1, VFB2, TRIP, DRVL1, DRVL2, COMP1, COMP2, VREG5, RF, VREF2, PGOOD1, PGOOD2, SKIPSEL1, SKIPSEL2, FUNC –0.1 6 VREG3 –0.1 3.5 –40 85 Operating free-air temperature UNIT V V °C ORDERING INFORMATION (1) TA PACKAGE (1) -40°C to 85°C Plastic Quad Flat Pack (32 Pin QFN) ORDERABLE PART NUMBER TRANSPORT MEDIA TPS51220RHBT Tape and Reel 250 TPS51220RHBR Tape and Reel 3000 QUANTITY For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI website at www.ti.com. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 3 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 ELECTRICAL CHARACTERISTICS over operating free-air temperature range, EN = 3.3V, VIN = 12V, V5SW = 5V (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 7 15 μA 80 120 μA SUPPLY CURRENT I(VINSDN) VIN shutdown current VIN shutdown current, TA = 25°C, No Load, EN = 0V, V5SW = 0 V I(VINSTBY) VIN Standby Current VIN shutdown current, TA = 25°C, No Load, EN1 = EN2 = V5SW = 0 V I(VBATSTBY) Vbat Standby Current Vbat standby current, TA = 25°C, No Load SKIPSEL2 = 2V, EN2 = open, EN1 = V5SW = 0V (1) I(V5SW) V5SW Supply Current V5SW current, TA = 25°C, No Load, ENx = 5V, VFBx = 1.05 V 500 μA TRIP = 5 V 1.2 mA TRIP = 0 V 1.4 mA VREF2 OUTPUT V(VREF2) VREF2 Output Voltage I(VREF2) < ±10 μA, TA = 25°C 1.98 2.00 2.02 I(VREF2) < ±100 μA, 4.5V < VIN < 25 V 1.97 2.00 2.03 V VREG3 OUTPUT V5SW = 0 V, I(VREG3) = 0 mA, TA = 25°C 3.279 3.313 3.347 V(VREG3) VREG3 Output Voltage V5SW = 0 V, 0 mA < I(VREG3) < 10 mA, 5.5 V < VIN < 25 V 3.135 3.300 3.400 I(VREG3) VREG3 Output Current VREG3 = 3 V 10 15 20 V5SW = 0 V, I(VREG5) = 0 mA, TA = 25°C 4.99 5.04 5.09 V5SW = 0 V, 0 mA < I(VREG5) < 100 mA, 6 V < VIN < 25 V 4.90 5.03 5.15 V5SW = 0 V, 0 mA < I(VREG5) < 100 mA, 5.5 V < VIN < 25 V 4.50 5.03 5.15 V5SW = 0 V, VREG5 = 4.5 V 100 150 200 V5SW = 5 V, VREG5 = 4.5 V 200 300 400 Turning on 4.55 4.7 4.8 Hysteresis 0.15 0.20 0.25 V mA VREG5 OUTPUT V(VREG5) VREG5 Output Voltage V V I(VREG5) VREG5 Output Current mA V(THV5SW) Switchover Threshold td(V5SW) Switchover Delay Turning on 7.7 ms R(V5SW) 5V SW Ron I(VREG5) = 100 mA 0.5 Ω V(VFB) VFB Regulation Voltage Tolerance TA = 25°C, No Load I(VFB) VFB Input Current VFBx = 1.05 V, COMPx = 1.8 V, TA = 25°C R(Dischg) CSNx Discharge Resistance ENx = 0 V, CSNx = 0.5 V, TA = 25°C V OUTPUT TA = –40°C to 85°C , No Load 0.9925 1.000 1.0075 0.990 1.000 1.010 –50 20 V 50 nA 40 Ω VOLTAGE TRANSCONDUCTANCE AMPLIFIER Gain VID Differential Input Voltage Range I(COMPSINK) COMP Maximum Sink Current COMPx = 1.8 V 33 μA I(COMPSRC) COMP Maximum Source Current COMPx = 1.8 V –33 μA (1) 4 TA = 25°C μS Gmv 500 –30 30 mV Specified by design. Detail external condition follows application circuit of Figure 54. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 ELECTRICAL CHARACTERISTICS (continued) over operating free-air temperature range, EN = 3.3V, VIN = 12V, V5SW = 5V (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT CURRENT AMPLIFIER GC Gain VIC Common mode Input Voltage Range VID Differential Input Voltage Range TRIP = 0V/2V, CSN = 5V, TA = 25°C (2) 3.333 TRIP = 3.3V/5V, CSN = 5V, TA = 25°C (2) 1.667 TA = 25°C 0 13 V –75 75 mV POWERGOOD PG in from lower 92.5% 95% 97.5% PG in from higher 102.5% 105% 107.5% V(THPG) PG threshold I(PG) PG sink Current PGOOD = 0.5 V t(PGDLY) PGOOD Delay Delay for PG in t(SSDYL) Soft Start Delay Delay for Soft Start, ENx = Hi to SS-ramp starts 140 μs t(SS) Soft Start Time Internal Soft Start 800 μs PG hysteresis 5% 5 0.8 1 mA 1.2 ms SOFTSTART FREQUENCY AND DUTY CONTROL f(SW) Switching Frequency Rf = 330 kΩ 273 303 333 Lo to Hi 0.7 1.3 2 V(THRF) RF Threshold f(SYNC) Sync Input Frequency Range (2) tONmin Minimum On Time V(DRVH) = 90% to 10%, No Load tOFFmin Minimum Off Time V(DRVH) = 10% to 90%, No Load tD Dead time Hysteresis 0.2 200 kHz V V 1000 kHz 120 150 ns 290 440 ns DRVH-off to DRVL-on 10 30 50 ns DRVL-off to DRVH-on 30 40 70 ns (2) V(DTH) DRVH-off threshold DRVH to GND V(DTL) DRVL-off threshold DRVL to GND (2) 1 V 1 V OUTPUT DRIVERS R(DRVH) DRVH resistance R(DRVL) DRVL resistance Source, V(VBST-DRVH) = 0.1 V 1.7 5 1 3 Source, V(VREG5-DRVL) = 0.1 V 1.3 4 Sink, V(DRVL-GND) = 0.1 V 0.7 2 Sink, V(DRVH-SW) = 0.1 V Ω Ω CURRENT SENSE V(OCL-ULV) Current limit threshold (ultra-low voltage) TRIP = 0V/2V, TA = 25°C 27 31 35 TRIP = 0V/2V 25 31 37 V(OCL-LV) Current limit threshold (low voltage) TRIP = 3.3V/5V, TA = 25°C 56 60 64 TRIP = 3.3V/5V 54 60 66 V(ZC) Zero cross detection comparator Offset 0.95V < CSNx < 12.6V –4 0 4 Negative current limit threshold (ultra-low voltage) TRIP = 0V/2V, TA = 25°C –24 –31 –38 V(OCLN-ULV) TRIP = 0V/2V –22 –31 –40 TRIP = 3.3V/5V, TA = 25°C –51 –60 –69 V(OCLN-LV) Negative current limit threshold (low voltage) TRIP = 3.3V/5V –49 –60 –71 (2) mV mV mV Specified by design. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 5 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 ELECTRICAL CHARACTERISTICS (continued) over operating free-air temperature range, EN = 3.3V, VIN = 12V, V5SW = 5V (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX 110% 115% 120% UNIT UVP, OVP AND UVLO V(OVP) OVP Trip Threshold t(OVPDLY) OVP Prop Delay V(UVP) UVP Trip Threshold t(UVPDLY) UVP Delay V(UVREF2) VREF2 UVLO Threshold V(UVREG3) VREG3 UVLO Threshold V(UVREG5) VREG5 UVLO Threshold OVP detect μs 1.5 UVP detect 65% 70% 73% 0.8 1 1.2 ms Wake up 1.7 1.8 1.9 V Hysteresis 75 100 125 mV 3 3.1 3.2 0.10 0.15 0.20 Wake up Hysteresis Wake up V 4.1 4.2 4.3 V 0.35 0.40 0.44 V Wake up 0.8 1 1.2 Hysteresis 0.1 0.2 0.3 0.45 0.50 0.55 0.1 0.2 0.3 Hysteresis INTERFACE AND LOGIC THRESHOLD V(EN) EN Threshold V(EN12) EN1/EN2 Threshold V(EN12SS) EN1/EN2 SS Start Threshold SS-ramp start threshold at external soft start V(EN12SSEND) EN1/EN2 SS End Threshold SS-End threshold at external soft start I(EN12) EN1/EN2 Source Current VEN1/EN2 = 0V Wake up Hysteresis (3) 1.5 SKIPSEL1/SKIPSEL2 Setting Voltage V 2 V 2 TRIP Setting Voltage Auto Skip 1.9 2.1 OOA Skip (min 1/8 Fsw) 3.2 3.4 OOA Skip (min 1/16 Fsw) 3.8 FUNC Setting Voltage I(TRIP) TRIP Input Current I(SKIPSEL) SKIPSEL Input Current μA V 1.5 V(OCL-ULV), Discharge OFF 1.9 2.1 V(OCL-LV), Discharge OFF 3.2 3.4 V(OCL-LV), Discharge ON 3.8 Current mode, OVP enable V(FUNC) 2.6 1.5 V(OCL-ULV), Discharge ON V(TRIP) V 1 Continuous V(SKIPSEL) V V 1.5 D-CAP mode, OVP disable 1.9 2.1 D-CAP mode, OVP enable 3.2 3.4 Current mode, OVP disable 3.8 TRIP = 0 V –1 1 TRIP =5 V –1 1 SKIPSELx = 0 V –1 1 SKIPSELx = 5 V –1 1 V μA μA BOOT STRAP SW V(FBST) Forward Voltage VVREG5-VBST, IF = 10 mA, TA = 25°C 0.10 0.20 V I(BSTLK) VBST Leakage Current VBST = 30 V, SW = 25 V 0.01 1.5 μA Shutdown temperature (3) 150 THERMAL SHUTDOWN T(SDN) (3) 6 Thermal SDN Threshold Hysteresis (3) 10 °C Specified by design. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 DEVICE INFORMATION PINOUT VBST2 SW2 25 GND DRVL2 27 26 30 5 6 20 19 7 8 18 17 PGOOD2 SKIPSEL2 CSP2 CSN2 VFB1 COMP1 FUNC VREG3 EN2 15 16 9 10 CSN1 DRVH2 VIN 3 4 24 23 22 21 VREF2 TRIP COMP2 VFB2 SKIPSEL1 CSP1 1 2 11 12 13 14 V5SW RF EN1 PGOOD1 EN DRVH1 29 28 32 31 SW1 VBST1 DRVL1 VREG5 RHB PACKAGE (TOP VIEW) TERMINAL FUNCTIONS TERMINAL NAME NO. DRVH1 1 DRVH2 24 SW2 25 SW1 32 VREG3 22 EN1 4 EN2 21 PGOOD1 5 PGOOD2 20 SKIPSEL1 6 SKIPSEL2 19 CSP1 7 CSP2 18 CSN1 8 CSN2 17 VFB1 9 VFB2 16 COMP1 10 COMP2 15 RF 3 I/O DESCRIPTION O High-side MOSFET gate driver outputs. Source 1.7Ω, sink 1.0Ω, SW-node referenced floating driver. Drive voltage corresponds to VBST to SW voltage. I/O High-side MOSFET gate driver returns. O Always alive 3.3V, 10mA Low Dropout Linear Regulator Output. Bypass to (signal) GND with more than 1μF ceramic capacitor. Runs from VIN supply or from VREG5 when it is switched over to V5SW input. I Channel 1 and Channel 2 SMPS Enable Pins. When turning on, apply greater than 0.55V and less than 6V. Connect to GND to disable. Adjustable soft-start capacitance to be attached here. O Power Good window comparator outputs for channel 1 and 2. The applied voltage should be less than 6V, and the recommended pull-up resistance value is from 100kΩ to 1MΩ. Skip Mode Selection pin. I GND: Continuous Conduction Mode VREF2: Auto Skip VREG3: OOA Auto Skip, max 7 skips (suitable for fsw < 400kHz) VREG5: OOA Auto Skip, max 15 skips (suitable for equal to or greater than 400kHz) I/O Current sense comparator inputs (+). An RC network with high quality X5R or X7R ceramic capacitor should be used to extract voltage drop across DCR. 0.1μF is a good value to start the design. See the current sensing scheme section for more details. I Current sense comparator inputs (–). See the current sensing scheme section. Used as power supply for the current sense circuit for 5V or higher output voltage setting. Also, used for output discharge terminal. I SMPS Voltage Feedback Inputs. Connect the feedback resistors divider, and should be referred to (signal) GND. I Loop Compensation Pin for current mode (Error Amplifier Output). Connect R (and C if required) from this pin to VREF2 for proper loop compensation with current mode operation. Ramp compensation adjustable pin for D-CAP mode, connect R from this pin to VREF2. 10kΩ is a good value to start the design. 6kΩ to 20kΩ can be chosen. See the D-CAP MODE section for more details. I/O Frequency Setting pin. Connect a frequency setting resistor to (signal) GND. Connect to an external clock for synchronization. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 7 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TERMINAL FUNCTIONS (continued) TERMINAL NAME NO. I/O DESCRIPTION Control architecture and OVP function Selection Pin. FUNC 11 I VREF2 13 O GND: Current mode, OVP enable VREF2: D-CAP mode, OVP disable VREG3: D-CAP mode, OVP enable VREG5: Current mode, OVP disable 2V Reference Output. Bypass to (signal) GND by 0.22μF ceramic capacitor. Overcurrent trip level and discharge mode selection pin. GND: V(OCL-ULV) , Discharge on VREF2: V(OCL-ULV), Discharge off VREG3: V(OCL-LV), Discharge off VREG5: V(OCL-LV), Discharge on TRIP 14 I EN 12 I VREF2 and VREG5 Linear Regulators Enable Pin. When turning on, apply greater than 1.2V and less than 6V. Connect to GND to Disable. VBST1 31 I Supply inputs for high-side NFET driver (boot strap Terminal). Connect a capacitor (0.1μF or greater is recommended) from this pin to respective SW terminal. Additional SB diode from VREG5 to this pin is an optional. O Low-side MOSFET gate driver outputs. Source 1.3Ω, sink 0.7Ω, GND referenced driver. VBST2 26 DRVL1 30 DRVL2 27 V5SW 2 I VREG5 switchover power supply input pin. VREG5 29 O 5V, 100mA Low Dropout Linear Regulator Output. Bypass to (power) GND using a 10μF ceramic capacitor. Runs from VIN supply. Internally connected to VBST and DRVL. Shuts off with EN. Switches over to V5SW when 4.8V or above is provided. VIN 23 I Supply Input for 5V and 3.3V Linear Regulator. Typically connected to VBAT. GND 28 -- Ground 8 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TYPICAL CHARACTERISTICS VIN SHUTDOWN CURRENT vs INPUT VOLTAGE VIN SHUTDOWN CURRENT vs JUNCTION TEMPERATURE 15 15 I(VINSDN) - Shutdown Current - μA I(VINSDN) - Shutdown Current - μA VIN = 12V 12 9 6 3 12 9 6 3 RT 0 -50 0 10 15 20 25 30 50 100 150 VI - VIN Input Voltage - V Figure 1. Figure 2. VIN STANDBY CURRENT vs JUNCTION TEMPERATURE VIN STANDBY CURRENT vs INPUT VOLTAGE 120 120 100 100 80 60 40 80 60 40 20 20 0 -50 0 TJ - Junction Temperature - °C I(VINSTBY) - Standby Current - mA I(VINSTBY) - Standby Current - mA 5 0 0 50 100 TJ - Junction Temperature - °C 150 5 Figure 3. 10 15 20 VI - VIN Input Voltage - V 25 30 Figure 4. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 9 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TYPICAL CHARACTERISTICS (continued) NO LOAD BATTERY CURRENT vs INPUT VOLTAGE NO LOAD BATTERY CURRENT vs INPUT VOLTAGE 1.0 1.0 EN = on, EN1 = on, EN2 = on 0.9 0.9 0.8 0.8 I(VBAT) - Battery Current - mA I(VBAT) - Battery Current - mA EN = on, EN1 = off, EN2 = on 0.7 0.6 0.5 0.4 0.3 0.2 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.1 0.0 5 10 15 20 0.0 25 5 VI - VIN Input Voltage - V 10 15 20 VI - VIN Input Voltage - V Figure 5. Figure 6. BATTERY CURRENT vs INPUT VOLTAGE VREF2 OUTPUT VOLTAGE vs OUTPUT CURRENT 25 2.02 1.0 EN = on, EN1 = on, EN2 = off VIN = 12V 0.9 VO(VREF2) - Output Voltage - V I(VBAT) - Battery Current - mA 0.8 0.7 0.6 0.5 0.4 0.3 0.2 2.01 2.00 1.99 0.1 0.0 5 10 15 20 VI - VIN Input Voltage - V 25 1.98 -100 Figure 7. 10 -50 0 50 100 IO(VREF2) - Output Current - μA Figure 8. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TYPICAL CHARACTERISTICS (continued) VREG3 OUTPUT VOLTAGE vs OUTPUT CURRENT VREG5 OUTPUT VOLTAGE vs OUTPUT CURRENT 3.40 5.10 VIN = 12V VO(VREG5) - Output Voltage - V VO(VREG3) - Output Voltage - V VIN = 12V 3.35 3.30 3.25 5.05 5.00 4.95 4.90 3.20 0 2 4 6 8 0 10 20 40 60 80 100 IO(VREG5) - Output Current - mA IO(VREG3) - Output Current - mA Figure 9. Figure 10. SWITCHING FREQUENCY vs JUNCTION TEMPERATURE FORWARD VOLTAGE OF BOOST SW vs JUNCTION TEMPERATURE 0.25 330 320 0.20 V(FBST) - Forward Voltage - V f(SW) - Switching Frequency - kHz RF = 330kΩ 310 300 290 0.10 0.05 280 270 -50 0.15 0 50 100 150 0.00 -50 TJ - Junction Temperature - °C Figure 11. 0 50 100 150 TJ - Junction Temperature - °C Figure 12. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 11 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TYPICAL CHARACTERISTICS (continued) VBST LEAKAGE CURRENT vs JUNCTION TEMPERATURE 150 1.5 130 1.2 Ilkg - VBST Leakage Current - μA OVP/UVP Threshold - % OVP/UVP THRESHOLD VOLTAGE vs JUNCTION TEMPERATURE OVP 110 90 70 0.9 0.6 0.3 UVP 50 -50 0 50 100 0.0 -50 150 TJ - Junction Temperature - °C Figure 13. Figure 14. CURRENT LIMIT THRESHOLD vs JUNCTION TEMPERATURE CURRENT LIMIT THRESHOLD vs JUNCTION TEMPERATURE 150 66 V(OCL-LV) - Current Limit Threshold - mV V(OCL-ULV) - Current Limit Threshold - mV 37 35 CSN = 1V CSN = 5V 33 31 CSN = 12V 29 27 25 -50 12 0 50 100 TJ - Junction Temperature - °C 0 50 100 150 64 CSN = 1V CSN = 5V 62 60 CSN = 12V 58 56 54 -50 0 50 100 TJ - Junction Temperature - °C TJ - Junction Temperature - °C Figure 15. Figure 16. Submit Documentation Feedback 150 Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TYPICAL CHARACTERISTICS (continued) 5-V OUTPUT VOLTAGE vs INPUT VOLTAGE 3.3-V OUTPUT VOLTAGE vs INPUT VOLTAGE 3.40 5.10 CCM VO2 - 3.3-V Output Voltage - V VO1 - 5-V Output Voltage - V CCM 5.05 IO = 0A 5.00 IO = 3A 4.95 IO = 6A 4.90 5 10 15 20 3.35 IO = 0A IO = 3A 3.30 IO = 6A 3.25 3.20 25 5 VI - VIN Input Voltage - V 10 15 25 VI - VIN Input Voltage - V Figure 17. Figure 18. 5-V EFFICIENCY vs OUTPUT CURRENT 5-V EFFICIENCY vs OUTPUT CURRENT 100 100 VIN = 7 V Auto-skip 90 80 OOA VIN = 12 V h - Efficiency - % h - Efficiency - % 20 60 40 80 VIN = 21 V 70 60 20 CCM Auto-skip VIN = 12V 0 0.001 0.01 0.1 1 IO1 - 5-V Output Current - A 10 50 0.001 0.01 0.1 1 10 IO1 - 5-V Output Current - A Figure 19. Figure 20. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 13 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TYPICAL CHARACTERISTICS (continued) 3.3-V EFFICIENCY vs OUTPUT CURRENT 3.3-V EFFICIENCY vs OUTPUT CURRENT 100 100 VIN = 7 V Auto-skip 90 80 h - Efficiency - % h - Efficiency - % VIN = 12 V OOA 60 40 5-V Switcher ON (Auto-skip) 20 CCM 80 VIN = 21 V 70 Auto-skip 60 50 5-V Switcher ON (Auto-skip) VIN = 12V 0 0.001 0.01 0.1 1 40 0.001 10 0.01 0.1 1 IO2 - 3.3-V Output Current - A IO2 - 3.3-V Output Current - A Figure 21. Figure 22. 5-V SWITCHING FREQUENCY vs OUTPUT CURRENT 3.3-V SWITCHING FREQUENCY vs OUTPUT CURRENT 400 400 VIN = 12V VIN = 12V 350 f(SW) - Swithching Frequency - kHz f(SW) - Swithching Frequency - kHz 350 CCM 300 250 200 OOA 150 100 CCM 300 250 200 OOA 150 100 50 50 Auto-skip Auto-skip 0 0 0 0.5 1 1.5 IO1 - 5-V Output Current - A 2 0 Figure 23. 14 10 0.5 1 1.5 IO2 - 3.3-V Output Current - A 2 Figure 24. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TYPICAL CHARACTERISTICS (continued) 5-V OUTPUT VOLTAGE vs OUTPUT CURRENT 3.3-V OUTPUT VOLTAGE vs OUTPUT CURRENT 3.40 5.10 Current Mode Rgv = 10k VIN = 12V OOA 5.05 VO2 - 3.3-V Output Voltage - V VO1 - 5-V Output Voltage - V Current Mode Rgv = 10k VIN = 12V Auto-skip 5.00 CCM 4.95 4.90 Auto-skip 3.30 CCM 3.25 3.20 0 1 2 3 4 IO1 - 5-V Output Current - A 5 OOA 3.35 6 0 1 2 3 4 IO2 - 3.3-V Output Current - A Figure 25. Figure 26. 5-V OUTPUT VOLTAGE vs OUTPUT CURRENT 3.3-V OUTPUT VOLTAGE vs OUTPUT CURRENT 6 3.40 5.10 Current Mode (No Droop) Rgv + C = 15K + 10nF VIN = 12V VO2 - 3.3-V Output Voltage - V Current Mode (No Droop) Rgv + C = 15K + 10nF VIN = 12V VO1 - 5-V Output Voltage - V 5 5.05 OOA Auto-skip 5.00 CCM 4.95 4.90 3.35 OOA 3.30 CCM 3.25 3.20 0 1 2 3 4 IO1 - 5-V Output Current - A 5 6 Auto-skip 0 Figure 27. 1 2 3 4 IO2 - 3.3-V Output Current - A 5 6 Figure 28. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 15 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TYPICAL CHARACTERISTICS (continued) 5-V OUTPUT VOLTAGE vs OUTPUT CURRENT 3.3-V OUTPUT VOLTAGE vs OUTPUT CURRENT 3.40 5.10 D-CAP mode Rgv = 10k Cout-ESR = 18mW VIN = 12V OOA 5.05 VO2 - 3.3-V Output Voltage - V VO1 - 5-V Output Voltage - V D-CAP mode Rgv = 10k Cout-ESR = 40mW VIN = 12V Auto-skip 5.00 CCM 4.95 4.90 3.35 OOA Auto-skip 3.30 CCM 3.25 3.20 0 1 2 3 4 IO1 - 5-V Output Current - A 5 6 0 1 2 3 4 IO2 - 3.3-V Output Current - A Figure 29. Figure 30. 5.0-V START-UP WAVEFORMS 3.3-V START-UP WAVEFORMS EN1 (5V/div) EN2 (5V/div) VO1 (2V/div) VO2 (2V/div) PGOOD1 (5V/div) 6 PGOOD2 (5V/div) VIN=12V Iout=6A VIN=12V Iout=6A t - Time - 1ms/div Figure 31. 16 5 t - Time - 1ms/div Figure 32. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TYPICAL CHARACTERISTICS (continued) 5.0-V SOFT-STOP WAVEFORMS 3.3-V SOFT-STOP WAVEFORMS EN1 (5V/div) EN2 (5V/div) VO1 (5V/div) VO2 (5V/div) PGOOD1 (5V/div) PGOOD2 (5V/div) DRVL1 (5V/div) DRVL2 (5V/div) t - Time - 1ms/div Figure 33. t - Time - 1ms/div Figure 34. 5.0-V LOAD TRANSIENT RESPONSE 3.3-V LOAD TRANSIENT RESPONSE VO2 (100mV/div) VO1 (100mV/div) IIND(5A/div) VIN=12V, Auto-skip IO1 (5A/div) IIND(5A/div) IO2 (5A/div) VIN=12V, Auto-skip t - Time - 100 ms/div t - Time - 100 ms/div Figure 35. Figure 36. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 17 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 TYPICAL CHARACTERISTICS (continued) 5.0-V BODE-PLOT – GAIN AND PHASE vs FREQUENCY 3.3-V BODE-PLOT – GAIN AND PHASE vs FREQUENCY Phase 40 Gain - dB 20 Gain 0 80 135 60 90 40 45 20 0 180 135 Phase 90 Gain 45 0 0 -20 -45 -20 -45 -40 -90 -40 -90 -135 -60 -180 -80 100 -60 VIN = 12V Current mode -80 100 1K 10K 100K 1M VIN = 12V Current Mode f - Frequency - kHz Phase - ° 60 180 Phase - ° Gain - dB 80 -135 -180 1K 10K f - Frequency - kHz Figure 37. 100K 1M Figure 38. 5.0-V SWITCH-OVER WAVEFORMS VREG5 (100mV/div) VO1 (100mV/div) t - Time - 2ms/div Figure 39. 18 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 DETAILED DESCRIPTION ENABLE AND SOFT START When EN is Low, the TPS51220 is in the shutdown state. The 3.3V LDO only stays alive, and consumes 7μA (typically). When EN becomes High, the TPS51220 is in the standby state. The 2V reference and the 5V LDO become enable, and consume about 80μA with no load condition, and are ready to turn on SMPS channels. Each SMPS channel is turned on when ENx becomes High. After ENx is set to high, the TPS51220 begins softstart, and ramps up the output voltage from zero to the target voltage with 0.8 ms. However, if a slower soft-start is required, an external capacitor can be tied from the ENx pin to GND. In this case, the TPS51220 charges the external capacitor with the integrated 2-μA current source. An approximate external soft-start time would be tEX-SS = CEX / IEN12, which means the time from ENx = 1V to ENx = 2V. The recommend capacitance is more than 2.2nF. 1) Internal Soft-start EN1 Vout1 800ms 140ms EN1<2V EN1>1V 2) External Soft-start EN1 External Soft-start time Vout1 Figure 40. Enable and Soft-start Timing Table 1. Enable Logic States EN EN1 EN2 VREG3 VREF2 VREG5 CH1 CH2 GND Don’t Care Don’t Care ON Off Off Off Off Hi Lo Lo ON ON ON Off Off Hi Hi Lo ON ON ON ON Off Hi Lo Hi ON ON ON Off ON Hi Hi Hi ON ON ON ON ON 3.3V, 10mA LDO (VREG3) A 3.3-V, 10mA, linear regulator is integrated in the TPS51220. This LDO services the some of the analog supply rail for IC and provides a handy standby supply for 3.3-V Always On voltage in the notebook system. Apply a 2.2-μF (at least 1-μF), high quality X5R or X7R ceramic capacitor from VREG3 to (signal) GND in adjacent to the IC. 2V, 100μA Sink/ Source Reference (VREF2) This voltage is used for the reference of the loop compensation network. Apply a 0.22-μF (at least 0.1-μF), high quality X5R or X7R ceramic capacitor from VREF2 to (signal) GND in adjacent to the IC. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 19 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 5.0V, 100mA LDO (VREG5) A 5.0-V, 100mA, linear regulator is integrated in the TPS51220. This LDO services the main analog supply rail for IC and provides the current for gate drivers until switch-over function becomes enable. Apply a 10-μF (at least 4.7-μF), high quality X5R or X7R ceramic capacitor from VREG5 to (power) GND in adjacent to the IC. VREG5 SWITCHOVER If the V5SW voltage becomes higher than 4.7V, the internal 5V-LDO is shut off and the VREG5 is shorted to V5SW by an internal MOSFET after an 7.7ms delay. When the V5SW voltage becomes lower than 4.5V, the internal switch is turned off and the internal 5V-LDO resumes immediately. BASIC PWM OPERATIONS The main control loop of the SMPS is designed as a fixed frequency, pulse width modulation (PWM) controller. It supports two control schemes; a peak current mode and a proprietary D-CAP mode. Current mode achieves stable operation in any type of capacitors including low ESR capacitor(s) such as ceramic or specialty polymer capacitors. D-CAP mode does not require an external compensation circuit, and is suitable for relatively larger ESR capacitor(s) configuration. These control schemes are selected with FUNC-pin; see Table 4. CURRENT MODE The current mode scheme uses the output voltage information and the inductor current information to regulate the output voltage. The output voltage information is sensed by VFBx pin. The signal is compared with the internal 1V reference and the voltage difference is amplified by a transconductance amplifier (VFB-AMP). The inductor current information is sensed by CSPx and CSNx pins. The voltage difference is amplified by another transconductance amplifier (CS-AMP). The output of the VFB-AMP indicates the target peak inductor current. If the output voltage goes down, the TPS51220 increases the target inductor current to raise the output voltage, on the other hand, if the output voltage goes up the TPS51220 decreases the target inductor current to reduce the output voltage. At the beginning of each clock cycle, the high-side MOSFET is turned on, or becomes ‘ON’ state. The high-side MOSFET is turned off, or becomes OFF state, after the inductor current becomes the target value which is determined by the combination value of the output of the VFB-AMP and a ramp compensation signal. The ramp compensation signal is used to prevent sub-harmonic oscillation of the inductor current control loop. The high-side MOSFET is turned on again at the next clock cycle. By repeating the operation in this manner, the controller regulates the output voltage. The synchronous low-side or the rectifying MOSFET is turned on each OFF state to keep the conduction loss minimum. D-CAP™ MODE With the D-CAP mode operation, the PWM comparator compares VREF2 with the combination value of the COMP voltage, VFB-AMP output, and the ramp compensation signal. When the both signals are equal at the peak of the voltage sense signal, the comparator provides the OFF signal to the high-side MOSFET driver. Because the compensation network is implemented on the part and the output waveform itself is used as the error signal, external circuit is simplified. Another advantage is its inherent fast transient response. A trade-off is a sufficient amount of ESR required in the output capacitor. The D-CAP™ mode is suitable for relatively larger output ripple voltage application. The inductor current information is used for the overcurrent protection and light load operation. 20 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 PWM FREQUENCY CONTROL The TPS51220 has a fixed frequency control scheme with 180° phase shift. The switching frequency can be determined by an external resistor which is connected between RF pin and GND, and can be calculated using Equation 1. 1 × 105 fsw éëkHz ùû = RF éëkΩ ùû (1) TPS51220 can also synchronize to more than 2.5V amplitude external clock by applying the signal to the RF pin. The set timing of channel-1 initiates at the raising edge (1.3V typ) of the clock and channel-2 initiates at the falling edge (1.1V typ). Therefore, the 50% duty signal makes both channels 180° phase shift. 1000 900 fSW - Frequency - kHz 800 700 600 500 400 300 200 100 0 100 200 300 400 500 RF - Resistance - kW Figure 41. Switching Frequency vs RF LIGHT LOAD OPERATION The TPS51220 automatically reduces switching frequency at light load condition to maintain high efficiency if Auto Skip or OOA™ mode is selected by SKIPSELx. This reduction of frequency is achieved by skipping pulses. As the output current decreases from heavy load condition, the inductor current is also reduced and eventually comes to the point that its peak touches a predetermined current, ILL(PEAK), which indicates the boundary between heavy load conduction and light load condition. Once the top MOSFET is turned on, the TPS51220 does not allow it to be turned off until it touches ILL(PEAK). This eventually causes an overvoltage condition to the output and pulse skipping. From the next pulse after zero-crossing is detected, ILL(PEAK) is limited by the ramp down signal which starts from 25% of the overcurrent limit setting (IOCL(PEAK): see the current protection session) toward 5% of IOCL(PEAK) over one switching cycle to prevent causing large ripple. The transition load point to the light load operation ILL(DC) can be calculated as follows; I LL(DC) + I LL(PEAK) * 0.5 I IND(RIPPLE) (2) (V - VOUT ) × VOUT 1 IIND(RIPPLE) = × IN L × fSW VIN (3) where fSW is the PWM switching frequency which is determined by RF resistor setting or external clock. Switching frequency versus output current in the light load condition is a function of L, f, VIN and VOUT, but it decreases almost proportional to the output current from the ILL(DC) given above; however, as the switching is synchronized with clock. Due to the synchronization, the switching waveform in boundary load condition (close to ILL(DC)) appears as a sub-harmonic oscillation; however, it is the intended operation. Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 21 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 If SKIPSELx is tied to GND, the TPS51220 works on a constant frequency of fSW regardless its load current. Inductor Current ILL(PEAK) ILL(DC) IIND(RIPPLE) 0 Time Figure 42. Boundary Between Pulse Skipping and CCM ILL(PEAK)Ramp = (0.25-0.2 × VOUT ) × IOCL(PEAK) VIN (4) Inductor Current 25% of IOCL(PEAK) ILL(PEAK) Ramp signal ILL(PEAK) 5% of IOCL(PEAK) 0 Time ton 1/fSW Figure 43. Inductor Current Limit at Pulse Skipping Table 2. Skip Mode Selection SKIPSELx GND VREF2 VREG3 VREG5 OPERATING MODE Continuous Conduction Auto Skip OOA Skip (max 7 skips, for <400 kHz) OOA Skip (max 15 skips, for equal to or greater than 400kHz) OUT OF AUDIO SKIP OPERATION Out-Of-Audio™ (OOA) light load mode is a unique control feature that keeps the switching frequency above acoustic audible frequencies toward virtually no load condition while maintaining best of the art high conversion efficiency. When OOA is selected, the switching frequency is kept higher than audible frequency range in any load condition. The TPS51220 automatically reduce switching frequency at a light load condition. OOA control circuit monitors the states of both MOSFETs and forces ON state if predetermined number of pulses are skipped. This means that the high-side MOSFET is turned on before the output voltage declines down to the target value, so that eventually an overvoltage condition is caused. The OOA control circuit detects this overvoltage condition and begins modulating the skip-mode on time to keep the output voltage. TPS51220 supports wide switching frequency range; therefore, the OOA skip mode has two selections, see Table 2. When 300kHz switching frequency is selected, max 7 skip (SKIPSEL=3.3V) makes the lowest frequency at 37.5kHz. If max 15 skip is chosen, it becomes 18.8kHz, hence max 7 skip is suitable for less than 400kHz, and max 15 skip is for equal to or greater than 400kHz. 22 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 99% DUTY CYCLE OPERATION In a low dropout condition such as 5V input to 5V output, the basic control loop tries to keep the high-side MOSFET 100% ON as a nature. However, with N-MOSFET used for the top switch, it is not possible to use the 100% on cycle to charge the boot strap capacitor. TPS51220 detects the 100% ON condition and inserts the OFF state at the appropriate time. HIGH-SIDE DRIVER The high-side driver is designed to drive high current, low rDS(on) N-channel MOSFET(s). The drive capability is represented by its internal resistance, which is 1.7Ω for VBSTx to DRVHx, and 1Ω for DRVHx to SWx. When configured as a floating driver, 5V bias voltage is delivered from VREG5 supply. The instantaneous drive current is supplied by the flying capacitor between VBSTx and SWx pins. The average drive current is equal to the gate charge at Vgs = 5V times switching frequency. This gate drive current as well as the low-side gate drive current times 5V makes the driving power which needs to be dissipated from TPS51220 package. A dead time to prevent shoot through is internally generated between high-side MOSFET off to low-side MOSFET on, and low-side MOSFET off to high-side MOSFET on. LOW-SIDE DRIVER The low-side driver is designed to drive high current low rDS(on) N-channel MOSFET(s). The drive capability is represented by its internal resistance, which are 1.3Ω for VREG5 to DRVLx and 0.7Ω for DRVLx to GND. The 5V bias voltage is delivered from VREG5 supply. The instantaneous drive current is supplied by an input capacitor connected between VREG5 and GND. The average drive current is also calculated by the gate charge at Vgs = 5V times switching frequency. CURRENT SENSING SCHEME In order to provide both good accuracy and cost effective solution, the TPS51220 supports external resistor sensing and inductor DCR sensing. An RC network with high quality X5R or X7R ceramic capacitor should be used to extract voltage drop across DCR. 0.1μF is a good value to start the design. CSPx and CSNx should be connected to positive and negative terminal of the sensing device respectively. TPS51220 has an internal current amplifier. The gain of the current amplifier, Gc, is selected by TRIP terminal. In any setting, the output signal of the current amplifier becomes 100mV at the OCL setting point. This means that the current sensing amplifier normalize the current information signal based on the OCL setting. Attaching a RC network recommended even with a resistor sensing scheme to get an accurate current sensing; see the external parts selection session for detailed configurations. CURRENT PROTECTION TPS51220 has cycle-by-cycle overcurrent limiting control. If the inductor current becomes larger than the overcurrent trip level, TPS51220 turns off high-side MOSFET, turns on low-side MOSFET and waits for the next clock cycle. IOCL(PEAK) sets peak level of the inductor current. Thus, the dc load current at overcurrent threshold, IOCL(DC), can be calculated as follows; I OCL(DC) + I OCL(PEAK) * 0.5 I IND(RIPPLE) (5) VOCL I OCL(PEAK) + RSENSE (6) where RSENSE is resistance of current sensing device and V(OCL) is overcurrent trip threshold voltage which is determined by TRIP pin voltages as shown in Table 3. In an overcurrent condition, the current to the load exceeds the current to the output capacitor thus the output voltage tends to fall down, and it will end up with crossing the undervoltage protection threshold and shutdown. Table 3. OCL Trip and Discharge Selection TRIP V(OCL) (OCL Trip voltage) Discharge GND VREF2 V(OCL-ULV) (Ultra Low Voltage) Enable Disable VREG3 VREG5 V(OCL-LV) (Low Voltage) Disable Enable Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 23 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 POWERGOOD The TPS51220 has powergood output for both switcher channels. The powergood function is activated after softstart has finished. If the output voltage becomes within ±5% of the target value, internal comparators detect power good state and the powergood signal becomes high after 1ms internal delay. If the output voltage goes outside of ±10% of the target value, the powergood signal becomes low after 1.5μs internal delay. Apply voltage should be less than 6V and the recommended pull-up resistance value is from 100kΩ to 1MΩ. OUTPUT DISCHARGE CONTROL The TPS51220 discharges output when ENx is low. The TPS51220 discharges outputs using an internal MOSFET which is connected to CSNx and GND. The current capability of these MOSFETs is limited to discharge the output capacitor slowly. If ENx becomes high during discharge, MOSFETs are turning on, and some output voltage remains. SMPS changes over to soft-start. PWM will begin after the target voltage overtakes the remaining output voltage. This function can be disabled as shown in Table 3. OVER/UNDERVOLTAGE PROTECTION TPS51220 monitors the output voltage to detect over and undervoltage. When the output voltage becomes 15% higher than the target value, the OVP comparator output goes high and the circuit latches as the high-side MOSFET driver OFF and the low-side MOSFET driver ON, and shuts off another channel. When the feedback voltage becomes lower than 70% of the target voltage, the UVP comparator output goes high and an internal UVP delay counter begins counting. After 1ms, TPS51220 latches OFF both high-side and low-side MOSFETs, and shuts off another channel. This UVP function is enabled after soft start has completed. OVP function can be disabled as Table 4. The procedures for restarting from these protection states are: 1. toggle EN 2. toggle EN1 and EN2 or 3. once hit UVLO Table 4. FUNC Logic States FUNC GND VREF2 VREG3 VREG5 OVP Enable Disable Enable Disable Control Scheme Current mode D-CAP mode D-CAP mode Current mode UVLO PROTECTION TPS51220 has undervoltage lock out protections (UVLO) for VREG5, VREG3 and VREF2. When the voltage is lower than UVLO threshold voltage, TPS51220 shuts off each output as Table 5. This is non-latch protection. Table 5. UVLO Protection CH1/ CH2 VREG5 VREG3 VREF2 VREG5 UVLO Off — On On VREG3 UVLO Off Off — Off VREF2 UVLO Off Off On — THERMAL SHUTDOWN TPS51220 monitors the temperature of itself. If the temperature exceeds the threshold value, TPS51220 shuts off both SMPS and 5V-LDO, and deceases the VREG3 current limitation to 5mA (typically). This is non-latch protection. 24 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 APPLICATION INFORMATION EXTERNAL PARTS SELECTION A buck converter using TPS51220 consists of linear circuits and a switching modulator. Figure 44 and Figure 45 show basic scheme. Voltage divider VFB Gmv DRVH PWM Control logic & Driver + + R2 VIN Switching Modulator Ramp comp. R1 + + 1.0V Lx Rs DRVL ESR RL Co COMP Cc Rgv Gmc Rgc VREF CSP + + CSN 2.0V Error Amplifier Figure 44. Simplified Current Mode Functional Blocks Voltage divider VFB Gmv DRVH PWM + + R2 + + 1.0V VIN Switching Modulator Ramp comp. R1 Control logic & Driver Lx Rs DRVL ESR RL Co COMP Rgv VREF + 2.0V Figure 45. Simplified D-CAP Mode Functional Blocks The external components can be selected by following manner. 1. Determine output voltage dividing resistors (R1 and R2: shown in Figure 44) using the next equation R1 + ǒV OUT * 1.0Ǔ R2 (7) For D-CAP mode, recommended R2 value is from 10kΩ to 20kΩ. 2. Determine switching frequency. Higher frequency allows smaller output capacitances, however, degrade efficiency due to increase of switching loss. Frequency setting resistor for RF-pin can be calculated by; Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 25 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 5 RF[kW] + 1 10 ƒ sw [kHz] (8) 3. Choose the inductor. The inductance value should be determined to give the ripple current of approximately 25% to 50% of maximum output current. Recommended ripple current rate is about 30% to 40% at the typical input voltage condition, next equation uses 33%. (VIN(TYP) - VOUT ) × VOUT 1 L= × 0.33 x IOUT(MAX) x fSW VIN(TYP) (9) The inductor also needs to have low DCR to achieve good efficiency, as well as enough room above peak inductor current before saturation. 4. Determine the OCL trip voltage threshold, V(OCL), and select the sensing resistor. The OCL trip voltage threshold is determined by TRIP pin setting. To use smaller value improves S/N ratio. Determine the sensing resistor using next equation. IOCL(PEAK) should be approximately 1.5 × IOUT(MAX) to 1.7 × IOUT(MAX). VOCL R SENSE + I OCL(PEAK) (10) 5. Determine Rgv. Rgv should be determined from preferable droop compensation value and is given by next equation based on the typical number of Gmv = 500μS. I OUT(MAX) 1 Rgv + 0.1 VOUT I OCL(PEAK) Gmv Vdroop (11) Rgv[kW] + 200 I OUT(MAX) I OCL(PEAK) V OUT[V] Vdroop[mV] (12) If no-droop is preferred, attach a series RC network circuit instead of single resistor. Series resistance is determined using Equation 13. Series capacitance can be arbitrarily chosen to meet the RC time constant, but should be kept under 1/10 of fo. For D-CAP mode, Rgv is used for adjusting ramp compensation. 10kΩ is a good value to start design with. 6kΩ to 20kΩ can be chosen. 6. Determine output capacitance Co to achieve a stable operation using the next equation. The 0 dB frequency, fo, should be kept under 1/3 of the switching frequency. Gmv Rgv ƒsw 1 ƒ0 + 5 t p I OCL(PEAK) V 3 Co OUT (13) Co u 15 p I OCL(PEAK) 1 VOUT Gmv Rgv ƒsw (14) For D-CAP mode, fo is determined by the output capacitor’s characteristics as below. ƒsw 1 ƒ0 + t 3 2p ESR Co 3 Co u 2p ESR ƒsw (15) (16) For better jitter performance, a sufficient amount of feedback signal is required at VFBx pin. The recommended signal level is approximately 30mV per tsw (switching period) of the ramping up rate, and more than 4mV of peak-to-peak voltage. 26 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 VFB signal 30mV VFBRIPPLE =VoRIPPLE x 1/Vout Time tSW = 1/fSW Figure 46. Required voltage feedback ramp signal 7. Calculate Cc. The purpose of this capacitance is to cancel zero caused by ESR of the output capacitor. If ceramic capacitor(s) is used, there is no need for Cc. If a combination of different capacitors is used, attach a RC network circuit instead of single capacitance to cancel zeros and poles caused by the output capacitors. With single capacitance, Cc is given in Equation 17. Cc + Co ESR Rgv (17) For D-CAP mode, basically Cc is not needed. 8. Choose MOSFETs Generally, the on resistance affects efficiency at high load conditions as conduction loss. For a low output voltage application, the duty ratio is not high enough so that the on resistance of high-side MOSFET does not affect efficiency; however, switching speed (tr and tf) affects efficiency as switching loss. As for low-side MOSFET, the switching loss is usually not a main portion of the total loss. RESISTOR CURRENT SENSING For more accurate current sensing with an external resistor, the following technique is recommended. Adding an RC filter to cancel the parasitic inductance of resistor, this filter value is calculated using Equation 18. Cx Rx + Lx Rs (18) This equation means time-constant of Cx and Rx should match the one of Lx (ESL) and Rs. VIN Ex-resistor DRVH Control logic & Driver L Rs Lx(ESL) DRVL Co CSP + Cx Rx CSN Figure 47. External Resistor Current Sensing Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 27 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 INDUCTOR DCR CURRENT SENSING To use inductor DCR as current sensing resistor (Rs), the configuration needs to change as below. However, the equation must be satisfied is the same as the one of resistor sensing. VIN Inductor DRVH Control logic & Driver Lx Rs(DCR) DRVL Co Rx CSP + Cx CSN Figure 48. Inductor DCR Current Sensing VIN Inductor DRVH Control logic & Driver Lx Rs(DCR) DRVL Co Rx CSP + Cx Rc CSN Figure 49. Inductor DCR Current Sensing With Voltage Divider TPS51220 has fixed V(OCL) point (60 mV or 30 mV). In order to adjust for DCR, a voltage divider can be configured as Figure 49. For Rx, Rc and Cx can be calculated as shown below, and overcurrent limitation value can be calculated as follows: Lx Cx × (Rx//Rc ) = Rs (19) Rx ) Rc 1 I OCL(PEAK) + VOCL Rs Rc (20) Figure 50 shows the compensation technique for the temperature drifts of the inductor DCR value. This scheme assumes the temperature rise at the thermistor (RNTC) is directly proportional to the temperature rise at the inductor. 28 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 Inductor Lx Rx Rs(DCR) RNTC Rc1 Rc2 CO CSP + Cx CSN Figure 50. Inductor DCR Current Sensing With Temperature Compensate LAYOUT CONSIDERATIONS Certain points must be considered before starting a PCB layout work using the TPS51220. Placement • Place RC network for CSP1 and CSP2 close to the IC pins. • Place bypass capacitors for VREG5, VREG3 and VREF2 close to the IC pins. • Place frequency-setting resistor close to the IC pin. • Place the compensation circuits for COMP1 and COMP2 close to the IC pins. • Place the voltage setting resistors close to the IC pins, especially when D-CAP mode is chosen. Routing (sensitive analog portion) • Use separate traces for; see Figure 51 – Output voltage sensing from current sensing (negative-side) – Output voltage sensing from V5SW input (when VOUT = 5V) – Current sensing (positive-side) from switch-node V5SW R1 VFB R2 H-FET Inductor Vout SW L-FET Cout R CSP C CSN Figure 51. Sensing Trace Routings • Use Kelvin sensing traces from the solder pads of the current sensing device (inductor or resistor) to current Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 29 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 sensing comparator inputs (CSPx and CSNx). (See Figure 52) Current sensing Device RC network next to IC Figure 52. Current Sensing Traces • • • • Use small copper space for VFBx. These are short and narrow traces to avoid noise coupling Connect VFB resistor trace to the positive node of the output capacitor. Use signal GND for VREF2 and VREG3 capacitors, RF and VFB resistors, and the other sensitive analog components. Placing a signal GND plane (underneath the IC, and fully covered peripheral components) on the internal layer for shielding purpose is recommended. (See Figure 53) Use a thermal land for PowerPAD™. Five or more vias, with 0.33-mm (13-mils) diameter connected from the thermal land to the internal GND plane, should be used to help dissipation. Do NOT connect the GND-pin to this thermal land on the surface layer, underneath the package. Routing (power portion) • Use wider/ shorter traces of DRVL for low-side gate drivers to reduce stray inductance. • Use the parallel traces of SW and DRVH for high-side MOSFET gate drive, and keep them away from DRVL. • Connect SW trace to source terminal of the high-side MOSFET. • Use power GND for VREG5, VIN and Vout capacitors and low-side MOSFETs. Power GND and signal GND should be connected near the IC GND terminal. (See Figure 53) TPS51220 0W resistor GND #28 GND-pin To inner Power-GND layer To inner Signal-GND plane Inner Signal-GND plane Figure 53. GND Layout Example 30 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 APPLICATION CIRCUITS VREG5 5V/100mA VBAT C12 2x10mF L1 4mH VBAT Q11 C01 10mF C14 0.1mF C24 0.1mF PGND PGND VO1 5V/6A C22 2x10mF Q21 Q12 L2 4mH VO2 3.3V/6A GND PGND PGND Q22 2 VO1 29 28 27 26 25 VREG5 GND DRVL2 VBST2 SW2 1 30 DRVL1 PGND 31 VBST1 PGND 32 SW1 C11 2x120mF DRVH1 PGND DRVH2 V5SW C21 2x220mF VIN PGND 24 23 VBAT VREG3 22 VREG3 3.3V/10mA EN2 21 EN2 PGOOD2 20 PGOOD2 SKIPSEL2 19 SKIPSEL2 CSP2 18 R01 330kW 3 RF 4 EN1 5 PGOOD1 6 SKIPSEL1 7 CSP1 C03 1mF GND EN1 PGOOD1 SKIPSEL1 R14 6.8kW TPS51220RHB (QFN32) GND R24 6.8kW 12 13 14 15 CSN2 VFB2 11 COMP2 10 TRIP 9 GND VREF2 EN EN CSN1 FUNC 8 VFB1 C13 0.1mF COMP1 PowerPAD R15 56kW C23 0.1mF R25 56kW 17 16 VREG5 VREF2 GND VO1 R11 120kW R12 30kW C15 100pF R21 62kW C02 0.22mF R13 10kW VO2 R23 10kW VREF2 GND C25 220pF R22 27kW VREF2 GND GND Figure 54. Current Mode, DCR Sensing, 5.0V/5A, 3.3V/5A, 300-kHz Table 6. Current Mode, DCR Sensing, 5.0V/5A, 3.3V/5A, 300-kHz SYMBOL SPECIFICATION MANUFACTURER PART NUMBER C11 2 × 120 μF/ 6.3 V/15-mΩ Panasonic EEFCX0J121R C12 2 × 10 μF/ 25 V Murata GRM32DR71E106K C21 2 × 220 μF/ 4.0 V/15-mΩ Panasonic EEFCX0G221R C22 2 × 10 μF/ 25 V Murata GRM32DR71E106K L1 4.0 μH, 10.3 A, 6.6-mΩ Sumida CEP125-4R0MC-H L2 4.0 μH, 10.3A, 6.6-mΩ Sumida CEP125-4R0MC-H Q11, Q21 30-V, 13.6-A, 9.5-mΩ IR IRF7821 Q12, Q22 30-V, 13.8-A, 5.8-mΩ IR IRF8113 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 31 TPS51220 www.ti.com SLVS785 – OCTOBER 2007 VREG5 5V/100mA VBAT R15 6mW VO1 5V/6A L1 3.3mH VBAT Q11 C12 2x10mF C01 10mF C14 0.1mF C22 2x10mF Q21 C24 0.1mF PGND PGND Q12 L2 3.3mH R25 6mW VO2 3.3V/6A GND PGND PGND Q22 2 VO1 29 28 27 26 25 VREG5 GND DRVL2 VBST2 SW2 1 30 DRVL1 PGND 31 VBST1 PGND 32 SW1 C11 2x220mF DRVH1 PGND DRVH2 V5SW C21 2x220mF VIN PGND 24 23 VBAT VREG3 22 VREG3 3.3V/10mA EN2 21 EN2 PGOOD2 20 PGOOD2 SKIPSEL2 19 SKIPSEL2 CSP2 18 CSN2 17 R01 270kW 3 RF 4 EN1 5 PGOOD1 6 SKIPSEL1 7 CSP1 C03 1mF GND EN1 PGOOD1 SKIPSEL1 TPS51220RHB (QFN32) GND 12 13 14 15 VFB2 11 COMP2 10 TRIP 9 GND VREF2 EN EN CSN1 FUNC 8 VFB1 C13 0.1mF COMP1 PowerPAD R14 1.2W C23 0.1mF 16 VREF2 GND R11 120kW R12 30kW C15 220pF R21 62kW C02 0.22mF VO1 R13 10kW VO2 GND R23 10kW VREF2 GND R24 1.2W C25 220pF R22 27kW VREF2 GND GND Figure 55. Current Mode, Ex-Resistor Sensing, 5.0V/5A, 3.3V/5A, 370-kHz Table 7. Current Mode, Ex-Resistor Sensing, 5.0V/5A, 3.3V/5A, 370-kHz SYMBOL SPECIFICATION MANUFACTURER PART NUMBER C11 2 x 220 μF/ 6.3 V/12-mΩ Panasonic EEFUE0J221R C12 2 x 10 μF/ 25 V Murata GRM32DR71E106K C21 2 x 220 μF/ 4.0 V/12-mΩ Panasonic EEFUE0G221R C22 2 x 10 μF/ 25 V Murata GRM32DR71E106K L1 3.3 μH, 10.3 A, 5.9-mΩ TOKO FDA1055-3R3M L2 3.3 μH, 10.3 A, 5.9-mΩ TOKO FDA1055-3R3M Q11, Q21 30-V, 13.6-A, 9.5-mΩ IR IRF7821 Q12, Q22 30-V, 13.8-A, 5.8-mΩ IR IRF8113 32 Submit Documentation Feedback Copyright © 2007, Texas Instruments Incorporated Product Folder Link(s) :TPS51220 PACKAGE OPTION ADDENDUM www.ti.com 31-Oct-2007 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TPS51220RHBR PREVIEW QFN RHB 32 3000 TBD Call TI Call TI TPS51220RHBT PREVIEW QFN RHB 32 250 TBD Call TI Call TI 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. 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