TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 17-V, 1.5-A, SYNCHRONOUS STEP-DOWN CONVERTER FEATURES • • • • • • • • • • • DESCRIPTION High-Efficiency Synchronous Step-Down Converter With up to 95% Efficiency 3.1-V to 17-V Operating Input Voltage Range Adjustable Output Voltage Range From 1.2 V to 16 V Fixed Output Voltage Options Available in 3.3 V and 5 V Synchronizable to External Clock Signal up to 1.4 MHz Up to 1.5-A Output Current High Efficiency Over a Wide Load Current Range Due to PFM/PWM Operation Mode 100% Maximum Duty Cycle for Lowest Dropout 20-µA Quiescent Current (Typical) Overtemperature and Overcurrent Protected Available in 16-Pin QFN Package The TPS6211x devices are a family of low-noise synchronous step-down dc-dc converters that are ideally suited for systems powered from a 2-cell Li-ion battery or from a 12-V or 15-V rail. The TPS6211x is a synchronous PWM converter with integrated – and P-channel power MOSFET switches. Synchronous rectification is used to increase efficiency and to reduce external component count. To achieve highest efficiency over a wide load current range, the converter enters a power-saving, pulse-frequency modulation (PFM) mode at light load currents. Operating frequency is typically 1 MHz, allowing the use of small inductor and capacitor values. The device can be synchronized to an external clock signal in the range of 0.8 MHz to 1.4 MHz. For low noise operation, the converter can be operated in PWM-only mode. In the shutdown mode, the current consumption is reduced to less than 2 µA. The TPS6211x is available in the 16-pin (RSA) QFN package, and operates over a free-air temperature range of –40°C to 85°C. APPLICATIONS • • • TPS62111 Efficiency vs Output Current Point-of-Load Regulation From 12-V Bus Organizers, PDAs, and Handheld PCs Handheld Scanners 100 4.2 V 90 TYPICAL APPLICATION 6.8 mH VI = 3.8 V to 17 V TPS62111 VIN VIN EN SW SW VINA PG VO = 3.3 V 1M 1 mF LBO AGND LBI FB CO = 22 mF 6.3 V Efficiency - % CI = 10 mF 25 V 80 5V 70 60 8.4 V 50 12 V 40 SYNC GND GND PwPD PGND PGND 30 VO = 3.3 V o TA = 25 C PFM Mode 20 10 0 0.0001 0.001 0.01 0.1 1 10 IO - Output Current- A 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. PowerPAD is a trademark 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 © 2005, Texas Instruments Incorporated TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 This device contains circuits to protect its inputs and outputs against damage due to high static voltages or electrostatic fields. These circuits have been qualified to protect this device against electrostatic discharges; HBM according to EIA/JESD22-A114-B, MM according EIA/JESD22-A115-A, and CDM according EIA/JESD22C101C; however, it is advised that precautions be taken to avoid application of any voltage higher than maximum-rated voltages to these high-impedance circuits. During storage or handling the device leads should be shorted together or the device should be placed in conductive foam. In a circuit, unused inputs should always be connected to an appropriate logic voltage level, preferably either VCC or ground. Specific guidelines for handling devices of this type are contained in the publication Guidelines for Handling Electrostatic-Discharge-Sensitive (ESDS) Devices and Assemblies available from Texas Instruments. ORDERING INFORMATION PLASTIC QFN 16 (RSA) (1) PIN (1) OUTPUT VOLTAGE LBI/LBO FUNCTIONALITY MARKING TPS62110 Adjustable 1.2 V to 16 V Standard TPS62110 TPS62111 3.3 V Standard TPS62111 TPS62112 5V Standard TPS62112 The RSA package is available in tape and reel. Add R suffix (TPS62110RSAR) to order quantities of 3000 parts per reel. Add T suffix (TPS62110RSAT) to order quantities of 250 parts per reel. ABSOLUTE MAXIMUM RATINGS (1) over operating free-air temperature range (unless otherwise noted) UNIT VCC Supply voltage at VIN, VINA –0.3 V to 20 V Voltage at SW VI –0.3 V to VI Voltage at EN, SYNC, LBO, PG –0.3 V to 20 V Voltage at LBI, FB –0.3 V to 7 V IO Output current at SW 2400 mA TJ Maximum junction temperature 150°C TA Operating free-air temperature –40°C to 85°C Tstg Storage temperature –65°C to 150°C Lead temperature 1,6 mm (1/16-inch) from case for 10 seconds (1) 300°C 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. DISSIPATION RATINGS (1) (1) PACKAGE TA ≤ 25°C POWER RATING DERATING FACTOR ABOVE TA = 25°C TA = 70°C POWER RATING TA = 85°C POWER RATING RSA 2.5 W 25 mW/°C 1.375 W 1W Based on a thermal resistance of 40 K/W soldered onto a high K board. RECOMMENDED OPERATING CONDITIONS MIN VCC Supply voltage at VIN , VINA 3.1 Maximum voltage at power-good, LBO, EN, SYNC TJ 2 Operating junction temperature –40 NOM MAX 17 UNIT V 17 V 125 °C TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 ELECTRICAL CHARACTERISTICS VI = 12 V, VO = 3.3 V, IO = 600 mA, EN = VI, TA = –40°C to 85°C (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT SUPPLY CURRENT VI Input voltage range I(Q) Operating quiescent current 3.1 IO = 0 mA, SYNC = GND, VI = 7.2 V, TA = 25°C (1) IO = 0 mA, SYNC = GND, VI = 17 V I(SD) Shutdown current 17 V 20 µA (1) 23 26 EN = GND 1.5 5 EN = GND, TA = 25°C, VI = 7.2 V 1.5 3 µA ENABLE VIH EN high-level input voltage VIL EN low-level input voltage 1.3 V 0.3 EN trip-point hysteresis 170 IIKG EN input leakage current EN = GND or VI, VI = 12 V I(EN) EN input current 0.6 V ≤ V(EN) ≤ 4 V V(UVLO) Undervoltage lockout threshold Input voltage falling 0.01 V mV 0.2 µA 10 20 µA 3 3.1 V 250 300 mV VI ≥ 5.4 V; IO = 350 mA 165 250 VI = 3.5 V; IO = 200 mA 340 VI = 3 V; IO = 100 mA 490 2.8 Undervoltage lockout hysteresis POWER SWITCH rDS(ON) P-channel MOSFET on-resistance P-channel MOSFET leakage current P-channel MOSFET current limit rDS(ON) N-channel MOSFET on-resistance N-channel MOSFET leakage current VDS = 17 V 0.1 VI = 7.2 V, VO = 3.3 V mΩ 1 2400 VI ≥ 5.4 V; IO = 350 mA 145 VI = 3.5 V; IO = 200 mA 170 VI = 3 V; IO = 100 mA 200 VDS = 17 V 0.1 µA mA 200 mΩ 2 µA POWER GOOD OUTPUT , LBI, LBO V(PG) Power good trip voltage Power good delay time VOL PG, LBO output low voltage IOL PG, LBO sink current PG, LBO output leakage current VO 1.6% VO ramping positive 50 VO ramping negative 200 V(FB) = 0.8 × VO nominal, IOL = 1 mA Low battery input trip voltage ILBI LBI input leakage current µs 0.3 1 V(FB) = VO nominal, V(LBI) = VI 0.01 Minimum supply voltage for valid power good, LBI, LBO signal VLBI V 0.25 3 Input voltage falling Low battery input trip-point accuracy µA V 1.256 10 V mA V 100 nA 1.5% VLBI,HYS Low battery input hysteresis 25 mV OSCILLATOR fS Oscillator frequency f(SYNC) Synchronization range VIH SYNC high-level input voltage VIL SYNC low-level input voltage (1) 900 CMOS-logic clock signal on SYNC pin 800 1000 1100 kHz 1400 kHz 1.5 V 0.3 V Device is not switching. 3 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 ELECTRICAL CHARACTERISTICS (continued) VI = 12 V, VO = 3.3 V, IO = 600 mA, EN = VI, TA = –40°C to 85°C (unless otherwise noted) PARAMETER Ilkg SYNC input leakage current TEST CONDITIONS MIN SYNC = GND or VIN SYNC trip-point hysteresis MAX 0.01 0.2 170 0.6 V ≤ V(SYNC) ≤ 4 V SYNC input current TYP Duty cycle of external clock signal 10 30% UNIT µA mV 20 µA 90% OUTPUT VO Adjustable output voltage range TPS62110 VFB Feedback voltage TPS62110 1.153 FB leakage current TPS62110 10 Feedback voltage tolerance TPS62110 VI = 3.1 V to 17 V; 0 mA < IO < 1500 mA (2) –2% 2% TPS62111 VI = 3.8 V to 17 V; 0 mA < IO < 1500 mA (2) –3% 3% TPS62112 VI = 5.5 V to 17 V; 0 mA < IO < 1500 mA (2) –3% 3% Fixed output voltage tolerance (3) 1.153 VI ≥ 3 V (once undervoltage lockout voltage exceeded) IO Maximum output current Efficiency Duty cycle range for main switches VI ≥ 3.5 V 500 VI ≥ 4.3 V 1200 VI ≥ 6 V 1500 VI = 7.2 V; VO = 3.3 V; IO = 600 mA (3) 4 nA V mA at 1 MHz 10% 100% 100 IO = 800 mA, VI = 12 V, Vo = 3.3 V µA 92% VI = 12 V, Vo = 5 V, Io = 600 mA Shutdown temperature (2) 100 5 Minimum ton time for main switch Start-up time V 100 Current into internal voltage divider for fixed voltage versions η 16 ns 145 °C 1 ms The maximum output current depends on the input voltage. See the maximum output current for further restrictions on the minimum input voltage. The output voltage accuracy includes line and load regulation over the full temperature range TA = -40°C to 85°C. See the section for no-load operation in this data sheet. TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 DEVICE INFORMATION PGND SW SW PG PIN ASSIGNMENT TOP VIEW 2 3 4 16 15 14 13 12 Exposed Thermal Pad 11 10 5 6 7 8 9 GND GND FB AGND VINA 1 SYNC LBO LBI PGND VIN VIN EN TERMINAL FUNCTIONS TERMINAL NAME NO. I/O DESCRIPTION EN 4 I Enable. A logic high enables the converter; logic low forces the device into shutdown mode reducing the supply current to less than 2 µA. FB 10 I Feedback pin for the fixed output voltage option. For the adjustable version, an external resistive divider is connected to this pin. The internal voltage divider is disabled for the adjustable version. LBO 6 O Open-drain, low-battery output. This pin is pulled low if LBI is below its threshold. GND 11, 12 I Ground LBI 7 I Low-battery input SW 14, 15 O Connect the inductor to this pin. This pin is the switch pin and connected to the drain of the internal power MOSFETS. PG 13 O Power good comparator output. This is an open-drain output. A pullup resistor should be connected between PG and VOUT. The output goes active high when the output voltage is greater than 98.4% of the nominal value. PGND 1, 16 I Power ground. Connect all power grounds to this pin. AGND 9 I Analog ground, connect to GND and PGND SYNC 5 I Input for synchronization to external clock signal. Synchronizes the converter switching frequency to an external clock signal with CMOS level: SYNC = HIGH: Low-noise mode enabled, fixed frequency PWM operation is forced SYNC = LOW (GND): Power save mode enabled, PFM/PWM Mode enabled VIN VINA PowerPAD™ 2, 3 I Supply voltage input (power stage) 8 I Supply voltage input (support circuits) Connect to AGND 5 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 FUNCTIONAL BLOCK DIAGRAM VI Current Limit Comparator + _ Undervoltage Lockout Bias Supply Vina REF Thermal Shutdown + _ Soft Start V I IAVG Comparator REF 1-MHz Oscillator V(COMP) P-Channel Power MOSFET Sawtooth Generator Comparator S + _ R Driver Shoot-Through Logic Control Logic SW N-Channel Power MOSFET Comparator High Comparator Low Comparator High 2 Load Comparator + _ SKIP Comparator + _ PG + _ Comparator High + Gm _ Comparator Low EN + R2 VREF = 1.153 V + _ + _ (See Note A) FB A. 6 LBO _ R1 Compensation LBI 1.256 V PGND GND For the adjustable version (TPS62110), the internal feedback divider is disabled and the FB pin is directly connected to the internal GM amplifier. TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 TYPICAL CHARACTERISTICS Table of Graphs FIGURE Efficiency vs Output current (5 V) 1, 2 Efficiency vs Output current (3.3 V) Maximum output current vs Input voltage Efficiency vs Output current (1.8 V) 7, 8 Efficiency vs Output current (1.5 V) 9, 10 3, 4, 5 6 Line transient response 11 Load transient response 12 Output ripple 13 Start-up timing 14 Switching frequency vs Input voltage 15 Quiescent current vs Input voltage 16 Graphs with VO = 1.8 V were taken using the circuit according to Figure 20. TPS62112 EFFICIENCY vs OUTPUT CURRENT TPS62112 EFFICIENCY vs OUTPUT CURRENT 100 100 90 90 80 80 8.4 V 70 Efficiency - % Efficiency - % 8.4 V 60 12 V 50 15 V 40 30 12 V 60 50 15 V 40 30 VO = 5 V o TA = 25 C PWM Mode 20 10 0 0.0001 70 0.001 0.01 0.1 IO - Output Current- A Figure 1. 1 20 10 10 VO = 5 V o TA = 25 C PFM Mode 0 0.0001 0.001 0.01 0.1 1 10 IO - Output Current- A Figure 2. 7 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 TPS62111 EFFICIENCY vs OUTPUT CURRENT TPS62111 EFFICIENCY vs OUTPUT CURRENT 100 100 90 90 4.2 V 80 80 70 Efficiency - % Efficiency - % 4.2 V 8.4 V 60 5V 50 12 V 40 30 5V 70 60 8.4 V 50 12 V 40 30 VO = 3.3 V o TA = 25 C PWM Mode 20 10 0 0.0001 0.001 0.01 0.1 1 VO = 3.3 V o TA = 25 C PFM Mode 20 10 0 0.0001 10 0.001 0.01 IO - Output Current- A Figure 3. Figure 4. TPS62111 EFFICIENCY vs OUTPUT CURRENT TPS62111 MAXIMUM OUTPUT CURRENT vs INPUT VOLTAGE VO = 3.3 V SYNC = 1.4 MHz o TA = 25 C PFM Mode IO - Output Current - mA Efficiency - % 80 70 8.4 V 60 5V 50 12 V 40 30 20 10 0 0.0001 8 0.001 0.01 0.1 10 1 IO - Output Current- A 100 90 0.1 1 10 2000 1900 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0 3.2 3.6 4 4.4 4.8 IO - Output Current- A VI - Input Voltage- V Figure 5. Figure 6. 5.2 5.6 6 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 TPS62110 EFFICIENCY vs OUTPUT CURRENT TPS62110 EFFICIENCY vs OUTPUT CURRENT 100 100 90 90 80 4.2 V 80 5V 70 60 Efficiency - % Efficiency - % 4.2 V 8.4 V 5V 50 12 V 40 30 8.4 V 60 50 40 12 V 30 VO = 1.8 V o TA = 25 C PWM Mode 20 10 0 0.0001 70 0.001 0.01 0.1 1 VO = 1.8 V o TA = 25 C PFM Mode 20 10 0 0.0001 10 0.001 Figure 8. TPS62110 EFFICIENCY vs OUTPUT CURRENT TPS62110 EFFICIENCY vs OUTPUT CURRENT 100 90 90 4.2 V 70 5V 8.4 V 50 40 12 V 30 10 4.2 V 70 5V 60 8.4 V 50 40 12 V 30 VO = 1.5 V o TA = 25 C PWM Mode 20 10 0 0.0001 1 80 Efficiency - % Efficiency - % Figure 7. 100 60 0.1 IO - Output Current- A IO - Output Current- A 80 0.01 0.001 0.01 0.1 IO - Output Current- A Figure 9. 1 VO = 1.5 V o TA = 25 C PFM Mode 20 10 10 0 0.0001 0.001 0.01 0.1 1 10 IO - Output Current- A Figure 10. 9 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 TPS62111 LINE TRANSIENT C1 = 5 V/div TPS62111 LOAD TRANSIENT VI = 8.4 V VO = 3.3 V ILOAD = 150 mA to 1350 mA TA = 25°C VO = 50 mV/div C2 = 50 mV/div IO = 500 mA/div VI = 7.2 V to 12 V VO = 3.3 V ILOAD = 800 mA TA = 25°C t − Time = 2 ms/div VI = 8.4 V, VO = 3.3 V t − Time = 20 µs/div Figure 11. Figure 12. TPS62111 OUTPUT RIPPLE TPS62111 START-UP TIMING ILOAD = 100 mA, TA = 25°C VI = 12 V, VO = 3.3 V ILOAD = 800 mA, TA = 25°C CH1 = 20 mV/div CH1 = 10 V/div CH2 = 5 V/div CH2 = 1 V/div CH3 = 5 V/div CH4 = 500 mA/div CH4 = 200 mA/div t − Time = 5 µs/div Figure 13. 10 t − Time = 200 µs/div Figure 14. TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 SWITCHING FREQUENCY vs INPUT VOLTAGE QUIESCENT CURRENT vs INPUT VOLTAGE 1000 50 VO = 12 V IO = 100 mA 45 o 85 C 40 980 o 970 25 C 960 o -40 C 950 940 930 Quiescent Current - mA Switching Frequency - kHz 990 35 30 20 910 5 4 5 6 0 7 8 9 10 11 12 13 14 15 16 17 VI - Input Voltage - V o -40 C 15 10 3 o 25 C 25 920 900 o 85 C 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 VI - Input Voltage - V Figure 15. Figure 16. The graphs were generated using the EVM with the setup according to Figure 17 unless otherwise noted. The output voltage divider was adjusted according to Table 4. Graphs for an output voltage of 5 V and 3.3 V were generated using TPS62111 and TPS62112 with R1 = 0 Ω and R2 = open. TDK 6.8 mH SLF7032T-6R8M1R6 Vbat VIN VIN EN open CI 10 mF / 25 V TDK C3225X5R1E106K TPS62110 VO SW SW 1 MW 1 MW R1 Cff PG VINA CO 22 mF / 16 V TDK C3225X7R1C226M 1 mF AGND LBO FB LBI R2 261 kW SYNC VIN or GND GND GND PwPD PGND PGND Figure 17. Test Setup 11 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 DETAILED DESCRIPTION OPERATION The TPS6211x is a synchronous step-down converter that operates with a 1-MHz fixed frequency pulse width modulation (PWM) at moderate-to-heavy load currents and enters the power save mode at light load current. During PWM operation, the converter uses a unique fast response voltage mode control scheme with input voltage feedforward. Good line and load regulation is achieved with the use of small input and output ceramic capacitors. At the beginning of each clock cycle initiated by the clock signal (S), the P-channel MOSFET switch is turned on, and the inductor current ramps up until the comparator trips and the control logic turns the switch off. The switch is turned off by the current limit comparator if the current limit of the P-channel switch is exceeded. After the dead time prevents current shoot through, the N-channel MOSFET rectifier is turned on, and the inductor current ramps down. The next cycle is initiated by the clock signal turning off the N-channel rectifier, and turning on the P-channel switch. The error amplifier as well as the input voltage determines the rise time of the sawtooth generator. Therefore, any change in input voltage or output voltage directly controls the duty cycle of the converter giving a very good line and load transient regulation. CONSTANT FREQUENCY MODE OPERATION (SYNC = HIGH) In constant frequency mode, the output voltage is regulated by varying the duty cycle of the PWM signal in the range of 100% to 10%. Connecting the SYNC pin to a voltage greater than 1.5 V forces the converter to operate permanently in the PWM mode even at light or no-load currents. The advantage is that the converter operates with a fixed switching frequency that allows simple filtering of the switching frequency for noise-sensitive applications. In this mode, the efficiency is lower compared to the power save mode during light loads. The N-MOSFET of the devices stay on even when the current into the output drops to zero. This prevents the device from going into discontinuous mode, and the device transfers unused energy back to the input. Therefore, there is no ringing at the output, which usually occurs in discontinuous mode. The duty cycle range in constant frequency mode is 100% to 10%. It is possible to switch from forced PWM mode to the power save mode during operation by pulling the SYNC pin LOW. The flexible configuration of the SYNC pin during operation of the device allows efficient power management by adjusting the operation of the TPS6211x to the specific system requirements. POWER SAVE MODE OPERATION (SYNC = LOW) As the load current decreases, the converter enters the power save mode operation. During power save mode, the converter operates with reduced switching frequency in pulse frequency modulation (PFM), and with a minimum quiescent current to maintain high efficiency. Whenever the average output current goes below the skip threshold, the converter enters the power save mode. The average current depends on the input voltage. It is about 200 mA at low input voltages and up to 400 mA with maximum input voltage. The average output current must be below the threshold for at least 32 clock cycles to enter the power save mode. During the power save mode, the output voltage is monitored with a comparator and the output voltage is regulated in to a typical value between the nominal output voltage and 0.8% above the nominal output voltage. When the output voltage falls below the nominal output voltage, the P-channel switch turns on. The P-channel switch is turned off as the peak switch current is reached. The N-channel rectifier is turned on, and the inductor current ramps down. As the inductor current approaches zero, the N-channel rectifier is turned off and the switch is turned on starting the next pulse. When the output voltage can not be reached with a single pulse, the device continues to switch with its normal operating frequency until the comparator detects the output voltage to be 0.8% above the nominal output voltage. This control method reduces the quiescent current to 20 µA (typical), and reduces the switching frequency to a minimum that achieves the highest converter efficiency. 12 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 DETAILED DESCRIPTION (continued) 1.6% 0.8% VO (nominal) -1.6% t Figure 18. Power Save Mode Output Voltage Thresholds The typical PFM (SKIP) current threshold for the TPS6211x is given by: VI I S K IP » 25 W (1) Equation 1 is valid for input voltages up to 7 V. For higher voltages, the skip current threshold is not increased further. The converter enters the fixed frequency PWM mode as soon as the output voltage falls below VO - 1.6% (nominal). SOFT START The TPS6211x has an internal soft-start circuit that limits the inrush current during start-up. This prevents possible voltage drops of the input voltage when a battery or a high-impedance power source is connected to the input of the TPS6211x. The soft start is implemented as a digital circuit increasing the switch current in steps of 300 mA, 600 mA, 1200 mA. The typical switch current limit is 2.4 A. Therefore, the start-up time depends on the output capacitor and load current. Typical start-up time with a 22-µF output capacitor and 800-mA load current is 1 ms. 100% DUTY CYCLE LOW DROPOUT OPERATION The TPS6211x offers the lowest possible input to output voltage difference while still maintaining operation with the use of the 100% duty cycle mode. In this mode, the P-channel switch is constantly turned on. This is particularly useful in battery-powered applications to achieve the longest operation time, taking full advantage of the whole battery voltage range. The minimum input voltage to maintain regulation depends on the load current and output voltage, and is calculated as: ( V I min = VO max + I O max × rDS ( on ) max + R( L ) ) (2) with: IOmax = maximum output current plus inductor ripple current rDS(on)max = maximum P-channel switch rDS(on) R(L) = dc resistance of the inductor VOmax = nominal output voltage plus maximum output voltage tolerance 13 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 DETAILED DESCRIPTION (continued) ENABLE Logic low on EN forces the TPS6211x into shutdown. In shutdown, the power switch, drivers, voltage reference, oscillator, and all other functions are turned off. The supply current is reduced to less than 2 µA in the shutdown mode. When the device is in thermal shutdown, the bandgap is forced to be switched on even if the device is set into shutdown by pulling EN to GND. If an output voltage is present when the device is disabled, which could be due to an external voltage source or a super capacitor, the reverse leakage current is specified under electrical characteristics. Pulling the enable pin high starts up the TPS6211x with the soft start. If the EN pin is connected to any voltage other than VI or GND, an increased leakage current of typically 10 µA and up to 20 µA can occur. UNDERVOLTAGE LOCKOUT The undervoltage lockout circuit prevents the device from misoperation at low-input voltages. It prevents the converter from turning on the switch or rectifier MOSFET under undefined conditions. The minimum input voltage to start up the TPS6211x is 3.4 V (worst case). The device shuts down at 2.8 V minimum. SYNCHRONIZATION If no clock signal is applied, the converter operates with a typical switching frequency of 1 MHz. It is possible to synchronize the converter to an external clock within a frequency range from 0.8 MHz to 1.4 MHz. The device automatically detects the rising edge of the first clock and synchronizes immediately to the external clock. If the clock signal is stopped, the converter automatically switches back to the internal clock and continues operation. The switch over is initiated if no rising edge on the SYNC pin is detected for a duration of four clock cycles. Therefore, the maximum delay time can be 6.25 µs if the internal clock has its minimum frequency of 800 kHz If the device is synchronized to an external clock, the power save mode is disabled, and the devices stay in forced PWM mode. Connecting the SYNC pin to the GND pin enables the power save mode. The converter operates in the PWM mode at moderate-to-heavy loads, and in the PFM mode during light loads which maintains high efficiency over a wide load current range. POWER GOOD COMPARATOR The power good (PG) comparator has an open-drain output capable of sinking 1 mA (typical). The PG is only active when the device is enabled (EN=high). When the device is disabled (EN=low), the PG pin is pulled to GND. The PG output is only valid after a 250-µs delay when the device is enabled, and the supply voltage is greater than the undervoltage lockout V(UVLO). PG is low during the first 250 µs after shutdown and in shutdown. The PG pin becomes active high when the output voltage exceeds 98.4% (typical) of its nominal value. Leave the PG pin unconnected when not used. LOW-BATTERY DETECTOR The low-battery output (LBO) is an open-drain type which goes low when the voltage at the low-battery input (LBI) falls below the trip point of 1.256 V ±1.5%. The voltage at which the low-battery warning is issued can be adjusted with a resistive divider as shown in Figure 19. The sum of resistors (R1 + R2) as well as the sum of (R5 + R6) is recommended to be in the 100-kΩ to 1-MΩ range for high efficiency at low output current. An external pullup resistor can be connected to OUT, or any other voltage rail in the voltage range of 0 V to 16 V. During start-up, the LBO output signal is invalid for the first 500 µs. LBO is high impedance when the device is disabled. If the low-battery comparator function is not used, connect LBI to ground. The low-battery detector is disabled when the device is disabled. The logic level of the LBO pin is not defined for the first 500 µs after EN is pulled high. When the LBI is used to supervise the battery voltage and shut down the TPS62111 at low-input voltages, the battery voltage rises when the current drops to zero. The implemented hysteresis on the LBI pin may not be sufficient for all types of batteries. Figure 19 shows how an additional external hysteresis can be implemented. 14 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 DETAILED DESCRIPTION (continued) 6.8 mH VI = 4.3 V to 17 V 2 3 4 TPS62110 VIN VIN EN SW SW 15 R3 R5 8 CI = 10 mF 25 V PG VINA 1 mF 9 7 AGND 6 FB 10 SYNC R4 Cff 10 pF R1 560 k 13 LBO LBI 5 R6 VO = 3.3 V 14 CO = 22 mF 6.3 V R2 300 k R7 GND GND PwPD PGND PGND 11 12 16 1 Figure 19. LBI With Increased Hysteresis NO LOAD OPERATION When the converter operates in the forced PWM mode and there is no load connected to the output, the converter regulates the output voltage by allowing the inductor current to reverse for a short time. THEORY OR OPERATION / DESIGN PROCEDURE Table 1. List of Inductors MANUFACTURER (1) TYPE INDUCTANCE DC RESISTANCE SATURATION CURRENT Coilcraft MSS6132-682 6.8 µH 65 mR (max) 1.5 A Epcos B82462G4682M 6.8 µH 50 mR (max) 1.5 A Sumida CDRH5D28-6R2 6.2 µH 33 mR (typ) 1.8 A SLF6028T-6R8M1R5 6.8 µH 35 mR (typ) 1.5 A SLF7032T-6R8M1R6 6.8 µH 41 mR (typ) 1.6 A 7447789006 6.8 µH 44 mR (typ) 2.75 A 7447779006 6.8 µH 33 mR (typ) 3.3 A 744053006 6.2 µH 45 mR (typ) 1.8 A TDK Wurth (1) The manufacturer's part numbers are used for test purposes only. Inductor Selection The control loop of the TPS6211x family requires a certain value for the output inductor and the output capacitor for stable operation. As long as the nominal value of L × C ≥ 6.2 µH × 22 µF, the control loop has enough phase margin and the device is stable. Reducing the inductor value without increasing the output capacitor (or vice versa) may cause stability problems. There are applications where it may be useful to increase the value of the output capacitor, e.g., for a low transient output voltage change. From a stability point of view, the inductor value could be decreased to keep the L × C product constant. However, there are drawbacks if the inductor value is decreased. A low inductor value causes a high inductor ripple current and therefore reduces the maximum dc output current. Table 2 gives the advantages and disadvantages when designing the inductor and output capacitor. 15 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 Table 2. Advantages and Disadvantages When Designing the Inductor and Output Capacitor INFLUENCE ON STABILITY ADVANTAGE DISADVANTAGE Less output voltage ripple Increase Cout (>22 µF) Uncritical Less output voltage overshoot / undershoot during load transient None Higher output voltage ripple Decrease Cout (<22 µF) Critical Increase inductor value >6.8 µH also High output voltage overshoot / undershoot during load transient None Less gain and phase margin Uncritical Increase L (>6.8 µH) Critical Decrease L (<6.8 µH) Increase output capacitor value > 22 µF also Less inductor current ripple More energy stored in the inductor → higher voltage overshoot during load transient Higher dc output current possible if operated close to the current limit Smaller current rise → higher voltage undershoot during load transient → do not decrease the value of Cout due to these effects High inductor current ripple esSmall voltage overshoot / undershoot dur- pecially at high input voltage ing load transient and low output voltage As it is shown in Table 2, the inductor value can be increased to higher values. For good performance, the peak-to-peak inductor current ripple should be less than 30% of the maximum dc output current. Especially at input voltages above 12 V, it makes sense to increase the inductor value in order to keep the inductor current ripple low. In such applications, the inductor value can be increased to 10 µH or 22 µH. Values above 22 µH should be avoided in order to keep the voltage overshoot during load transient in an acceptable range. After choosing the inductor value, two additional inductor parameters should be considered: 1. current rating of the inductor 2. dc resistance The dc resistance of the inductance directly influences the efficiency of the converter. Therefore, an inductor with lowest dc resistance should be selected for highest efficiency. In order to avoid saturation of the inductor, the inductor should be rated at least for the maximum output current plus the inductor ripple current which is calculated as: 1 D I L = V O ´ L V O V I f ´ I L m ax = IO m ax + D I L 2 (3) Where: f = Switching frequency (1000 kHz typical) L = Inductor value ∆IL = Peak-to-peak inductor ripple current IL(max) = Maximum inductor current The highest inductor current occurs at maximum VI. A more conservative approach is to select the inductor current rating just for the maximum switch current of the TPS6211x which is 2.4 A (typically). See Table 1 for recommended inductors. OUTPUT CAPACITOR SELECTION A 22-µF (typical) output capacitor is needed with a 6.8-µH inductor. For an output voltage greater than 5 V, a 33-µF (minimum) output capacitor is required for stability. For best performance, a low ESR ceramic output capacitor is needed. Just for completeness, the RMS ripple current is calculated as: 16 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 VO VI L ´ f 1 I R M S (C O ) = V O ´ ´ 1 2 ´ 3 (4) The overall output ripple voltage is the sum of the voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charge and discharging the output capacitor: VO VI L ´ f 1 DV O = VO ´ æ 1 ´ çç + RESR è 8 ´ CO ´ f ö ÷ ÷ ø (5) Where the highest output voltage ripple occurs at the highest input voltage VI. INPUT CAPACITOR SELECTION The nature of the buck converter is a pulsating input current; therefore, a low ESR input capacitor is required for best input voltage filtering, and minimizing the interference with other circuits caused by high input voltage spikes. The input capacitor should have a minimum value of 10 µF and can be increased without any limit for better input voltage filtering. The input capacitor should be rated for the maximum input ripple current calculated as: IR M S = IO m ax ´ VO V I æ VO ö ÷ ´ çç 1 V I ÷ø è (6) The worst-case RMS ripple current occurs at D = 0.5 and is calculated as: IRMS = IO/2. Ceramic capacitors show a good performance because of their low ESR value, and they are less sensitive against voltage transients compared to tantalum capacitors. Place the input capacitor as close as possible to the input pin of the IC for best performance FEEDFORWARD CAPACITOR SELECTION The feedforward capacitor (Cff) is needed to compensate for parasitic capacitance from the feedback pin to GND. Typically, a value of 4.7 pF to 22 pF is needed for an output voltage divider with a equivalent resistance (R1 in parallel with R2) in the 150-kΩ range. The value can be chosen based on best transient performance and lowest output voltage ripple in PFM mode. RECOMMENDED CAPACITORS It is recommended that only X5R or X7R ceramic capacitors be used as input/output capacitors. Ceramic capacitors show a dc-bias effect. This effect reduces the effective capacitance when a dc-bias voltage is applied across a ceramic capacitor, as on the output and input capacitor of a dc/dc converter. The effect may lead to a significant capacitance drop especially for high input/output voltages and small capacitor packages. See the manufacturer's data sheet about the performance with a dc bias voltage applied. It may be necessary to choose a higher voltage rating or nominal capacitance value in order to get the required value at the operating point. The capacitors listed in Table 3 have been tested with the TPS62110 with good performance. Table 3. List of Capacitors MANUFACTURER Taiyo Yuden PART NUMBER SIZE VOLTAGE CAPACITANCE TMK316BJ106KL 1206 25 V 10 µF EMK325BJ226KM 1210 16 V 22 µF 25 V 10 µF 16 V 22 µF 25 V 10 µF C3225X5R1E106M TDK C3225X7R1C226M C3216X5R1E106MT 1210 1206 TYPE Ceramic Ceramic 17 TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 APPLICATION INFORMATION 6.8 mH VI = 3.5 V to 17 V 2 3 4 TPS62110 VIN VIN EN SW SW 15 R3 1 MW R5 8 CI = 10 mF 25 V PG VINA 1 mF 9 7 AGND 5 R6 13 LBO 6 FB 10 LBI VO = 1.8 V 14 R4 1 MW R1 220 kW Cff 10 pF CO = 2 x 22 mF 6.3 V R2 390 kW SYNC GND GND PwPD PGND PGND 11 A. 12 1 16 For an output voltage lower than 2.5 V, an output capacitor of 33 µF or greater is recommended to improve load transient. Figure 20. Standard Connection for Adjustable Version V O = V F B æ VO R 1 = R 2 ´ çç è V F B R 1 + R 2 R 2 ´ ö ÷ - R 2 ÷ ø (7) VFB = 1.153 V Table 4. Recommended Resistors OUTPUT VOLTAGE R1 R2 NOMINAL VOLTAGE TYPICAL Cff 9V 680 kΩ 100 kΩ 8.993 V 22 pF 5V 510 kΩ 150 kΩ 5.073 V 10 pF 3.3 V 560 kΩ 300 kΩ 3.305 V 10 pF 2.5 V 390 kΩ 330 kΩ 2.515 V 10 pF 1.8 V 220 kΩ 390 kΩ 1.803 V 10 pF 1.5 V 100 kΩ 330 kΩ 1.502 V 10 pF 6.8 mH VI = 5.5 V to 17 V 2 3 4 8 CI = 10 mF 25 V TPS62112 15 SW SW VIN VIN EN 1 MW PG VINA 1 mF 9 7 VO = 5 V 14 13 LBO 6 FB 10 AGND LBI 5 SYNC GND GND PwPD PGND PGND 11 12 1 16 Figure 21. Standard Connection for Fixed Voltage Version 18 CO = 22 mF 10 V TPS62110 TPS62111 TPS62112 www.ti.com SLVS585 – JULY 2005 6.8 mH VI = 9.3 V to 17 V 2 3 4 8 CI = 10 mF 25 V TPS62110 VIN VIN EN SW SW 7 AGND 13 LBO 6 FB 10 LBI 5 VO = 9 V 14 1 MW PG VINA 1 mF 9 15 Cff R1 680 kW 22 pF CO = 33 mF 16 V R2 100 kW SYNC GND GND PwPD PGND PGND 11 A. 12 1 16 For an output voltage greater than 5 V, an output capacitor of 33 µF minimum is required for stability. Figure 22. Application With 9-V Output 19 PACKAGE OPTION ADDENDUM www.ti.com 27-Sep-2005 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty TPS62110RSAR ACTIVE QFN RSA 16 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62110RSARG4 ACTIVE QFN RSA 16 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62110RSAT ACTIVE QFN RSA 16 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62110RSATG4 ACTIVE QFN RSA 16 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62111RSAR ACTIVE QFN RSA 16 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62111RSARG4 ACTIVE QFN RSA 16 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62111RSAT ACTIVE QFN RSA 16 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62111RSATG4 ACTIVE QFN RSA 16 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62112RSAR ACTIVE QFN RSA 16 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62112RSARG4 ACTIVE QFN RSA 16 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62112RSAT ACTIVE QFN RSA 16 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS62112RSATG4 ACTIVE QFN RSA 16 250 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) 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. 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. 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