TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com 3-V to 20-V INTEGRATED FET HOT SWAP CONTROLLER Check for Samples: TPS2420 FEATURES DESCRIPTION • • • • • • • • • • • • • The TPS2420 provides highly integrated load protection for 3-V to 20-V applications. The TPS2420 protects loads, minimizes inrush current, and safely shuts down in the event of a fault. The programmable fault current threshold starts the fault timer while allowing the current to pass to the load uninhibited. The programmable current limit threshold sets the maximum current allowed into the load, for both inrush and severe load faults. Both events use the programmable timer which inhibits all current to the load when it expires. 1 2 Integrated 30-mΩ Pass MOSFET 3.0-V to 20-V Bus Operation Programmable Fault Current Programmable Hard Current Limit Programmable Fault Timer Internal MOSFET Power Limiting Foldback Latching and Auto-Retry Operation Analog Current Monitor Output Powergood Output Fault Output Indicator 4 mm × 4 mm QFN –40°C to 125°C Junction Temperature Range UL Listed - File Number E169910 The dual protection thresholds are useful in applications such as disk drives. The start-up and seek currents are typically higher than the nominal current and during this time the load needs a low impedance path to deliver the power. If a failure at the load occurs, the current limit does not allow the current to exceed the programmed threshold. This protects both the load and the integrity of the power supply. The internal MOSFET is protected by power limit circuitry which ensures that the MOSFET remains within its safe operating area (SOA) during all operating states. APPLICATIONS • • • • RAID Arrays Telecommunications Plug-In Circuit Boards Disk Drives The TPS2420 also allows the system to monitor load currents with no need for a shunt in the power path. The gain of the current monitor can be scaled to the application. Fault and power good outputs are provided for improved system management and sequencing control. This device can be programmed to either latch-off or retry in the event of a fault. All of this functionality is packed into a 16-pin 4 × 4 mm QFN package. 3.0 V to 20.0 V VOUT 1 VIN VOUT 12 2 VIN VOUT 11 3 VIN 4 VIN VOUT 10 Input Voltage Bus (A) CVIN 15-V SMAJ15A TPS2420 } PG 14 16 EN IMON 13 LTCH GND IMAX IFLT CT 6 5 7 8 9 40.2 kW 49.9 kW (A) Optional: to system monitor 63.4 kW 0.1 mF CLOAD Output to voltage bus or DC/DC converter FLT 15 (A) UDG-09017 (A) Required only in systems with lead and/or load inductance. 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. 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 © 2009–2011, Texas Instruments Incorporated TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. PRODUCT INFORMATION (1) (1) DEVICE JUNCTION TEMPERATURE PACKAGE MARKING TPS2420 –40°C to 125°C RSA (4-mm × 4-mm QFN) TPS2420 For the most current package and ordering information, see the Package Option Addendum at the end of this document, or visit the device product folder on www.ti.com. ABSOLUTE MAXIMUM RATINGS (1) (2) over operating free-air temperature range (unless otherwise noted) VALUE UNIT VIN, VOUT Voltage range –0.3 to 25 FLT, PG Voltage range –0.3 to 20 IFAULT, IMAX, CT Voltage FLT, PG Output sink current 10 EN Input voltage range –0.3 to 6 V LTCH Input current (LTCH internally clamped to 3 V) LTCH = 0 V 35 μA Voltage range CT (3), IFLT (3), IMAX, IMON (3), LTCH –0.3 to 3 2500 ESD rating, CDM 400 Operating junction temperature range Tstg Storage temperature range (2) (3) mA ESD rating, HBM TJ (1) V 1.75 V Internally Limited °C –65 to 150 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 GND. Do not apply voltage to these pins. DISSIPATION RATINGS (1) (1) (2) (3) (4) PACKAGE θJA LOW K (2), °C/W θJA HIGH K (3), °C/W θJA BEST (4), °C/W RSA 211 55 50 Tested per JEDEC JESD51, natural convection. The definitions of high-k and low-k are per JESD 51-7 and JESD 51-3. Low-k (2 signal – no plane, 3-inch by 3-inch board, 0.062 inch thick, 1 oz. copper) test board with the pad soldered, and an additional 0.12 inch 2 of top-side copper added to the pad. High-k is a (2 signal – 2 plane) test board with the pad soldered. The best case thermal resistance is obtained using the recommendations per SLMA002A (2 signal – 2 plane with the pad connected to the plane). RECOMMENDED OPERATING CONDITIONS PARAMETER MIN MAX VIN, VOUT Voltage range 3 20 V EN Voltage range 0 5 V FLT, PG Voltage range 0 20 V FLT, PG Output sink current 0 1 mA LTCH Voltage range CT TJ 2 Junction temperature Submit Documentation Feedback UNIT 0 3 V 0.1 100 μF –40 125 °C Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com ELECTRICAL CHARACTERISTICS over operating free-air temperature range (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX 2.6 2.85 2.9 UNIT INPUT SUPPLY (VIN) VUVLO Undervoltage lockout VIN increasing Hysteresis Bias current 150 V mV V EN = 2.4 V 25 100 μA V EN = 0 V 3.9 5 mA 33 50 5 7.5 0.77 1.0 V A INPUT/OUTPUT RON On-resistance RVIN-VOUT, IVOUT < IIMAX or IVOUT < (ISET × 1.25), 1 A ≤ IVOUT ≤ 4.5 A PLIMIT Power limit VIN= 12 V, COUT = 1000 μF EN: 3V → 0 V Reverse diode voltage VOUT > VIN, EN = 5 V, IIN = –1 A 3 mΩ W FAULT CURRENT (FLT) I FLT Fault current threshold IVOUT increasing, ICT from sinking to sourcing, pulsed test R FLT = 200 kΩ 0.8 1 1.2 R FLT = 100 kΩ 1.8 2 2.2 R FLT = 49.9 kΩ 3.6 4 4.4 RIMAX = 100 kΩ 1.6 2 2.4 RIMAX = 66.5 kΩ 2.6 3 3.4 RIMAX = 40.2 kΩ 4.6 5 5.4 CURRENT LIMIT (IMAX) IIMAX Current limit program IVOUT ↑, VVIN-VOUT = 0.3 V, pulsed test A FAULT TIMER (CT) Charge/Discharge current Threshold voltage D ON/OFF fault duty cycle ICT sourcing, VCT = 1 V, In current limit 29 35 41 ICT sinking, VCT = 1 V, drive CT to 1 V, measure current 1.0 1.4 1.8 VCT increasing 1.3 1.4 1.5 VCT decreasing 0.1 0.16 0.3 2.8% 3.7% 4.6% VVOUT = 0 V μA V ENABLE (EN) Threshold voltage Input bias current V EN decreasing 0.8 1.0 1.5 V Hysteresis 50 150 250 mV –1.5 0 0.5 2 1 0.5 350 500 30 50 V EN = 2.4 V (sinking) V EN = 0.2 V (sourcing) Turn on propagation delay Turn off propagation delay VIN = 3.3 V, ILOAD = 1 A, V EN ↑ 90% × VIN VIN = 3.3 V, ILOAD = 1 A, V EN 10% × VIN μA : 2.4 V → 0.2 V, VOUT: μs : 0.2 V → 2.4V, VOUT: ↓ Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 3 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com ELECTRICAL CHARACTERISTICS (continued) over operating free-air temperature range (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 0.2 0.4 V 1 μA FAULT (IFLT) VOL Low-level output voltage VCT = 1.8 V, I FLT = 1 mA IIFLT Leakage current V FLT = 18 V POWERGOOD (PG) V PG PG threshold V(VIN-VOUT) decreasing 0.4 0.5 0.65 Hysteresis 0.1 0.25 0.4 0.2 0.4 VOL Low-level output voltage I PG = 1 mA I PG Leakage current V PG = 18 V 1 V μA CURRENT MONITOR (IMON) Ratio ILOAD/IIMON Offset current (sourcing) IOUT = 500 mA 30 56 80 IOUT = 2.0 A 50 61 70 IOUT = 4.50 A 56 61 66 IVIN = 0 A Clamp voltage A/mA –10 –2 0 μA 2.6 2.75 2.9 V LATCH FUNCTION (LTCH) Low threshold voltage Auto retry mode High threshold Latch mode 0.8 Input bias current VLTCH = 3.0 V –1.0 0.2 1.0 VLTCH = 0.2 V –50 –25 0 2.0 V μA THERMAL SHUTDOWN Thermal shutdown Junction temperature increasing Hysteresis 4 160 10 Submit Documentation Feedback °C Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com TPS2420 FUNCTIONAL BLOCK DIAGRAM IOUT 1 VIN 2 3 4 V(DS) Detector + S - R R FT LCA + + R IOUT / 66k 13 IMON 1.0V + 11 VOUT 10 10 uA Q Pump Constant Power Engine GND 5 I(D) Detector 12 1.6 x ILIM 15 FLT IMAX 7 + + IOUT ______ 200k 8 PWRG\ + IFLT CT Charge THERMAL SHUTDOWN 34 uA CT 1.35 V 9 S Q R Q FLT + FLT 1.25 uA 33 uA + 200 mV LTCH 6 VIN 10M 1.5V + PWRG\ EN 16 VIN Internal Rail VOUT 14 PG + + 18M VIN -300mV 2.7 / 2.6 Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 5 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com DEVICE INFORMATION VIN 1 VIN 2 EN FLT PG IMON PINOUT DIAGRAM 16 15 14 13 12 VOUT 11 VOUT TPS2420 4 9 5 6 7 8 IFLT VIN IMAX 10 VOUT LTCH 3 GND VIN CT TERMINAL FUNCTIONS NAME EN PIN NO. I/O 16 I Device is enabled when this pin is pulled low. I Power in and control supply voltage . If low, the TPS2420 will attempt to restart after an overcurrent fault. If floating (high) the device will latch off after an overcurrent fault and will not attempt to restart until EN or VIN is cycled off and on. DESCRIPTION 1 VIN 2 3 4 LTCH 6 I GND 5 — IMAX 7 I A resistor to ground sets the current limit level. IFLT 8 I A resistor to ground sets the fault current level. CT 9 I/O A capacitor to ground sets the fault time. IMON 13 O A scaled down current which indicates the current through the device. O Output to the load. Ground. 10 VOUT 11 12 PG 14 O Power Good low represents the output voltage is within 300 mV of the input voltage. FLT 15 O Fault low indicated the fault time has expired and the FET is switched off. 6 Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com PIN DESCRIPTION CT: Connect a capacitor form CT to GND to set the fault time. The fault timer starts when the fault current threshold is exceeded, charging the capacitor with 36 μA from GND towards an upper threshold of 1.4 V. If the capacitor reaches the upper threshold, the internal pass MOSFET is turned off. The MOSFET will stay off until EN is cycled if a latching version is used. If an auto-retry version is used, the capacitor will discharge at 5 μA to 0.2 V and then re-enable the pass MOSFET. When the device is disabled, CT is pulled to GND through a 100-kΩ resistor. The timer period must be chosen long enough to allow the external load capacitance to charge. The fault timer period is selected using the following formula where TFAULT is the minimum timer period in seconds and CCT is in Farads. C CT = TFAULT 38.9 ´ 10 3 (1) This equation does not account for component tolerances. In autoretry versions, the second and subsequent retry timer periods will be approximately 85% as long as the first retry period. In autoretry versions, the fault timer discharges the capacitor for a nominal TSD in seconds with CCT in Farads per the following equation. TSD = 1.0 ´ 106 ´ CCT (2) The nominal ratio of on to off times represents about a 3% duty cycle when a hard fault is present on the output of an autoretry version device. FLT: Open-drain output that pulls low on any condition that causes the output to open. These conditions are either an overload with a fault time-out, or a thermal shutdown. FLT becomes operational before UV, when VIN is greater than 1 volt. GND: This is the most negative voltage in the circuit and is used as reference for all voltage measurements unless otherwise specified. IFLT: A resistor connected from this pin to ground sets the fault current threshold (IFAULT). Currents between the fault current threshold and the current limit are permitted to flow unimpeded for the period set by the fault timer programmed on CT. This permits loads to draw momentary surges while maintaining the protection provided by a lower average-current limit. IFLT may not be set below 1 A to maintain the Fault Current Limit threshold accuracy listed in Electrical Characteristics. Some parts may not current limit or fault as expected. The fault timer implemented by CT starts charging CT when current through VIN exceeds IFAULT. If the current doesn’t drop below the IFAULT level before VCT reaches its upper threshold, the output will be shut off. The fault current resistor is set by the following formula where IFAULT is in Amperes and RRFLT is in ohms. RIFLT = 200kW IFAULT (3) IMAX: A resistor connected from this pin to ground sets IMAX. The TPS2420 will limit current to IMAX. If the current does not drop below the IFAULT level before the timer times out then the output will be shut off. RMAX is set by the formula: RIMAX = 201kW IIMAX (4) IMAX must be set sufficiently larger than IFAULT to ensure that lMAX could never be less than IFAULT, even after taking tolerances into account. EN: When this pin is pulled low, the device is enabled. The input threshold is hysteretic, allowing the user to program a startup delay with an external RC circuit. EN is pulled to VIN by a 10-MΩ resistor, pulled to GND by 16.8 MΩ and is clamped to ground by a 7-V Zener diode. Because high impedance pullup/down resistors are used to reduce current draw, any external FET controlling this pin should be low leakage. Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 7 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com VIN: Input voltage to the TPS2420. The recommended operating voltage range is 3 V to 18 V. All VIN pins should be connected together and to the power source. VOUT: Output connection for the TPS2420. When switched on the output voltage will be approximately: VOUT = VIN - 0.04 ´ IOUT (5) All VOUT pins should be connected together and to the load. LTCH: When pulled low the 2420 will attempt to restart after a fault. If left floating or pulled high the TPS2420 will latch off after a fault. This pin is internally clamped at 3 V and is pulled to the internal 3-V supply by diode in series with a 100-kΩ resistor. PG: Active low, Open Drain output, Power Good indicates that there is no fault condition and the output voltage is within 0.5 V of the input voltage. PG becomes operational before UV, whenever VIN is greater than 1 V. IMON: This is a scaled analog output of IVIN. Select RIMON based on the maximum allowed A/D input voltage (VAD_FS) and the desired full-scale current in VIN (IVIN_FS) per the following equation RIMON = 63kW ´ VAD _ IN(max ) ILOAD(max ) (6) This pin is clamped at 2.5 V to protect A/D converters. It is reccomended that IMON be ignored until after PG asserts because the IMON output is accurate only after VOUT > 3 V. 8 Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com TYPICAL CHARACTERISTICS CURRENT LIMIT vs JUNCTION TEMPERATURE FAULT CURRENT vs JUNCTION TEMPERATURE 2.20 2.20 RMAX = 100 k 2.15 IFAULT – Fault Current – A IIMAX – Current Limit – A 2.10 2.50 2.00 1.95 1.90 2.10 2.50 2.00 1.95 1.90 1.85 1.85 1.80 –50 0 50 – Junction Temperature – °C TJ 100 1.80 –50 150 TJ 0 50 100 – Junction Temperature – °C Figure 1. Figure 2. POWER LIMIT vs JUNCTION TEMPERATURE SUPPLY CURRENT vs JUNCTION TEMPERATURE 8.0 7.5 RFLT = 100 k 2.15 150 24 ILOAD = 1 A Sleep Mode 7.0 ISUPPLY – Supply Current – mA PLIMIT – Power Limit Level – W 22 6.5 6.0 5.5 5.0 4.5 4.0 20 18 16 14 12 3.5 3.0 –50 0 TJ 50 100 150 10 –50 – Junction Temperature – °C Figure 3. 0 TJ 50 100 150 – Junction Temperature – °C Figure 4. Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 9 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com TYPICAL CHARACTERISTICS (continued) OUTPUT CURRENT vs JUNCTION TEMPERATURE FAULT TIMER THRESHOLD VOLTAGE vs JUNCTION TEMPERATURE –32.0 ILOAD = 2 A VTHRESH – Fault Timer Threshold Voltage -– V –32.2 1.50 IIMON – Output Current – mA –32.4 –32.6 –32.8 –33.0 –33.2 –33.4 –33.6 –33.8 –34.0 –50 0 TJ 50 100 150 1.45 1.40 1.35 1.30 –50 – Junction Temperature – °C Figure 5. 10 0 TJ 50 100 150 – Junction Temperature – °C Figure 6. Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com TYPICAL CHARACTERISTICS Figure 7. 12-V Startup into 15-Ω, 700-μF Load Figure 8. 12-V Input Addded to an 8-Ω Load Figure 9. Failed Startup into a 4-Ω Load Figure 10. 12-V Soft Overload, 3-A to 4.2-A, Power Limit Not Tripped Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 11 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com TYPICAL CHARACTERISTICS (continued) 12 Figure 11. Firm Overload, 3-A to 5.4 A, Power Limit Tripped Figure 12. 12-V Hard Overload, 3.6-A Load then Short Figure 13. Power Dissipation During 12-V Startup into a 60-Ω, 800-μF Load Figure 14. Power Dissipation During 12-V Startup into a 15-Ω, 140-μF Load Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com TYPICAL CHARACTERISTICS (continued) Figure 15. Startup into a 1-Ω Load Figure 16. Firm Overload, Load Stepped From 3.8 A to 5.5 A Figure 17. Hard Overload, Load Stepped from 3.8 A to 7.1 A Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 13 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com APPLICATION INFORMATION If EN is tied to GND at startup and VIN does not ramp quickly the TPS2420 may momentarily turn off then on during startup. This can happen if a capacitive load momentarily pulls down the input voltage below the UV threshold. If necessary, this can be avoided by delaying EN assertion until VIN is fully up. Maximum Load The power limiting function of the TPS2420 provides very effective protection for the internal FET. Expectedly, there is a supply voltage dependent maximum load which the device will be able to power up. Loads above this level may cause the device to shut off current before startup is complete. Neglecting any load capacitance, the maximum load ( minimum load resistance ) is calculated using the equation; V 2 RMIN = IN 12 (7) Adding load capacitance may reduce the maximum load which can be present at start up. Transient Protection The need for transient protection in conjunction with hot-swap controllers should always be considered. When the TPS2420 interrupts current flow, input inductance generates a positive voltage spike on the input and output inductance generates a negative voltage spike on the output. Such transients can easily exceed twice the supply voltage if steps are not taken to address the issue. Typical methods for addressing transients include; • Minimizing lead length/inductance into and out of the device • Voltage Suppressors (TVS) on the input to absorb inductive spikes • Shottky diode across the output to absorb negative spikes • A combination of ceramic and electrolytic capacitors on the input and output to absorb energy • Use PCB GND plane The following equation estimates the magnitude of these voltage spikes: VSPIKE(absolute ) = VNOM + ILOAD ´ L C where • • • • VNOM is the nominal supply voltage ILOAD is the load current C is the capacitance present at the input or output of the TPS2420 L equals the effective inductance seen looking into the source or the load (8) Calculating the inductance due to a straight length of wire is shown in Equation 9. æ 4´L ö - 0.75 ÷ (nH) Lstraightwire » 0.2 ´ L ´ ln ç D è ø where • • L is the length of the wire D is diameter of the wire (9) Some applications may require the addition of a TVS to prevent transients from exceeding the absolute ratings if sufficient capacitance cannot be included. 14 Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com APPLICATION INFORMATION Operation When load current exceeds the user programmed fault limit (IFAULT) during normal operation the fault timer starts. If load current drops below the IFAULT threshold before the fault timer expires, normal operation continues. If load current stays above the IFAULT threshold the fault timer expires and a fault is declared. When a fault is declared a device operating in latch mode turns off and can be restarted by cycling power or toggling the EN signal. A device operating in retry mode attempts to turn on at a 3% duty cycle until the fault is cleared. When the IMAX limit is reached during a fault the device goes into current limit and the fault timer keeps running. IMAX can be programmed by the user by connecting a resistor from the IMAX pin to GND. Startup When power is first applied to a load with discharged capacitors there is a large inrush current. The inrush is controlled by the TPS2420 by initially entering the power limit mode and turning on the fault timer. See Figure 19. As the charge builds on the capacitor, the current increases to IMAX. When the capacitor is fully charged, current output is set by the dc load value, The fault timer is turned off. The FET is then fully enhanced and the power good signal is true. In order to start properly, the fault timer must be set to exceed the capacitor charge time. When the load has a resistive component as well as capacitive, the fault time needs to be increased because current to the resistive load is unavailable to charge the capacitor. The startup time for some selected loading is given in Table 1. Table 1 data was taken with IFAULT set to 4 A and IMAX set to 5 A. Lower current settings of TPS2420 do not have a great influence on the start up timer because of operation at power limit. Load capacitance and dc resistance was selected for a measured start time. The start time is measured from the assertion of the EN pin to the assertion of the PG pin. Table 1. Start Time for Input Voltage and Output Loading (1) INPUT VOLTAGE (V) LOAD CAPACITANCE (μF) 220 5 1000 220 12 1000 (1) DC LOAD RESISTANCE (Ω) START TIME (ms) OPEN 2.5 5 2.7 12 2.6 OPEN 4 5 4 12 4 OPEN 4.4 5 No start 12 7 OPEN 14 5 No start 12 23 IFAULT = 4 A, IMAX = 5 A. Some combinations of loading and current limit settings exceed the 5-W power limit of the internal MOSFET. The output voltage will not turn on regardless of the fault time setting. One way to work with the physical limits that create this problem is to allow the power manager to charge only the capacitive component of the load and use the PG signal to turn on the resistive component. This is common usage in dc-to-dc converters and other electrical equipment with power good inputs. Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 15 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com Start Up Into a Short The controller attempts to power on into a short for the duration of the timer. Figure 20 shows a small current resulting from power limiting the internal MOSFET. This happens only once for the latch off mode. For the retry mode, Figure 24 shows this cycle repeating at an interval based on the CT time. Shutdown Modes Hard Overload - Fast Trip When a hard overload causes the load current to exceed 1.6 × IMAX the TPS2420 immediately shuts off current to the load without waiting for the fault timer to expire. After such a shutoff the TPS2420 enters into startup mode and attempts to apply power to the load. If the hard overload is caused by a current transient, then a normal startup can be expected with a low probability of disruption to the load, assuming there is sufficient load capacitance to hold up the load during the fractions of a millisecond that make up the fast trip/restart cycle. If the hard overload is caused by a real, continuous failure then the TPS2420 goes into current limit during the attempt at restart. The timer starts and eventually runs out, shutting off current to the load. See the fast trip figures 22 and 23. When the hard overload occurs the current is turned off, the PG pin becomes false, and the FLT pin stays false. The FLT pin becomes true only when the fault timer times out. Overcurrent Shutdown Overcurrent shutdown occurs when the output current exceeds IMAX for the duration of the fault timer. Overcurrent shutdown is the circuit breaker type protection of equipment. Figure 23 shows the step rise in output current. The increased current is on for the duration of the timer. At conclusion of the timer, the output is turned off. Design Example The TPS2420 Design shown in Figure 25 supports 12 V to operate a hot plugged disk drive. The 12 V specification for a disk drive is approximately 1-A operating current and 2-A typical spin-up. Selecting a 2.5 A setting for IFAULT would allow some margin for the operating current and satisfy the start current requirements. Calculate RRFLT using equation Equation 10 or select it using Table 2. RIFLT = 200kW 200,000 ´ = 80 (kW ) IFAULT 2.5 (10) The IMAX setting, 3.5 A, is set by RRMAX in Equation 11. RIMAX = 16 201kW 201,000 ´ = 57.4 (kW ) IIMAX 3.5 Submit Documentation Feedback (11) Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com Because IFAULT satisfies the spin up current, the timer can be set for the additional loading of charging the capacitor. Estimate approximately 20 ms. Use either Equation 12 or Table 2 to estimate the capacitance. CCT = TFAULT 38.9 ´ 103 = 20 ´ 10-3 ´ 103 = 0.514 ´ 10-6 38.9 (12) For a scaled analog readback of the current from VIN, set the IMON resistor. In Equation 13 , the VAD_INMAX is the desired full scale A/D converter voltage. The largest value of VAD_INMAX 2.5 V. ILOADMAX is the full scale current, 2.5 A. RIMON = (63,000 ´ V AD _ IN(max ) ILOAD(max ) )= (63,000 ´ 2.5) = 63 (kW ) 2.5 (13) The read-back voltage at the IMON pin, VIMON, indicates the instantaneous current output. Using equation Equation 14 again, determine the current output for example, a 1.8-V VIMON. Substitute VIMON for VAD_INMAX and ILOAD for ILOADMAX and solve for ILOAD, (Equation 14). ILOAD = (63,000 ´ VIMON ) = (63,000 ´ 1.8 ) = 1.81 RIMON 62,500 (A ) (14) Layout Support Components Locate all TPS2420 support components, RSET, CT, etc. or any input or output voltage clamps, close to their connection pin. Connect the other end of the component to the inner layer GND without trace length. PowerPad™ When properly mounted the PowerPad package provides significantly greater cooling ability than an ordinary package. To operate at rated power the Power Pad must be soldered directly to the PC board GND plane directly under the device. The PowerPad is at GND potential and can be connected using multiple vias to inner layer GND. Other planes, such as the bottom side of the circuit board can be used to increase heat sinking in higher current applications. Refer to Technical Briefs: PowerPAD™ Thermally Enhanced Package (TI Literature Number SLMA002) and PowerPAD™ Made Easy (TI Literature Number SLMA004) for more information on using this PowerPadTM package.These documents are available at www.ti.com (Search by Keyword). Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 17 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com APPLICATION PLOTS 18 Figure 18. Start Up Into an RC Load (PG) Figure 19. Start Up Into an RC Load (CT) Figure 20. Startup Into a Short Circuit Output Figure 21. Device Output Short Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com Figure 22. FLT on Device Output Short Figure 23. Overcurrent Shutdown Figure 24. Retry Into an Output Short Circuit Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 19 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 12 V VIN C1 1 mF 15 V D1 SMAJ15A RIMAX 57.6 kW www.ti.com 1 VIN EN 16 2 VIN FLT 15 3 VIN PG 14 4 VIN 5 GND 6 LTCH 7 IMAX 8 R1 10 kW R2 10 kW IMON 13 U1 TPS2420RSA 12 V VOUT VOUT 12 VOUT 11 RIMON 63.4 kW VOUT 10 PowerPAD IFLT CT 9 RIFLT 80.6 kW D2 MBR130LSFT1 CT 560 nF GND GND UDG-09018 Figure 25. TPS2420 Reference Design, 12-V, 2.5-A Steady State Current, 5-A Max Current NOTE D1, D2, and C1 are required only in systems with significant feed and/or load inductance. To alter parameters IIAX, IFAULT, IIMON or CCT use the formulas in the Pin Description section or use Table 2 . Table 2. Typical Design Examples 20 IFAULT (A) RIFLT (kΩ) IIMAX (A) RIMAX (kΩ) CCT (μF) TFAULT (ms) TSD (ms) ILOAD(max) (A) RIMON (kΩ) 158 1 200 2 100 0.022 0.86 22 1 1.5 133 2.5 80.6 0.047 1.83 47 1.5 105 2 100 3 65.5 0.1 3.89 100 2 78.7 2.5 80.6 3.5 56.2 0.22 8.56 220 2.5 63.4 3 65.5 4 49.9 0.47 18.28 470 3 52.3 3.5 56.2 4.5 44.2 0.68 26.45 680 3.5 45.3 4 49.9 5 40.2 1 38.9 1000 4 39.2 Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 TPS2420 SLUS903D – JANUARY 2009 – REVISED SEPTEMBER 2011 www.ti.com REVISION HISTORY Changes from Revision A (March, 2010) to Revision B Page • Changed PRODUCT INFORMATION Note 1 to: "For the most current package and ordering information, see the Package Option Addendum at the end of this document, or visit the device product folder on www.ti.com." ..................... 2 • Changed TSD (ms) column values ...................................................................................................................................... 20 Changes from Revision B (July 2010) to Revision C • Page Added UL Listed - File Number E169910 ............................................................................................................................. 1 Changes from Revision C (August 2010) to Revision D Page • Changed CURRENT LIMIT (IMAX) to CURRENT IMAX ...................................................................................................... 3 • Added IFLT may not be set below 1 A to maintain the Fault Current Limit threshold accuracy listed in the Electrical Characteristics table. Some parts may not current limit or fault as expected. ..................................................................... 7 • Changed IILIM to IMAX ........................................................................................................................................................... 15 • Changed IILIM to IMAX ........................................................................................................................................................... 15 • Changed IILIMIT to IMAX ......................................................................................................................................................... 16 • Changed IILIMIT to IMAX ......................................................................................................................................................... 16 Submit Documentation Feedback Copyright © 2009–2011, Texas Instruments Incorporated Product Folder Link(s): TPS2420 21 PACKAGE OPTION ADDENDUM www.ti.com 2-Dec-2011 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Qty Eco Plan (2) Lead/ Ball Finish MSL Peak Temp (3) TPS2420RSAR ACTIVE QFN RSA 16 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR TPS2420RSAT ACTIVE QFN RSA 16 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Samples (Requires Login) (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant TPS2420RSAR QFN RSA 16 3000 330.0 12.4 4.25 4.25 1.15 8.0 12.0 Q2 TPS2420RSAT QFN RSA 16 250 180.0 12.4 4.25 4.25 1.15 8.0 12.0 Q2 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) TPS2420RSAR QFN RSA 16 3000 367.0 367.0 35.0 TPS2420RSAT QFN RSA 16 250 210.0 185.0 35.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46C and to discontinue any product or service per JESD48B. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily performed. TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use of any TI components in safety-critical applications. In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and requirements. Nonetheless, such components are subject to these terms. No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties have executed a special agreement specifically governing such use. Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI has specifically designated certain components which meet ISO/TS16949 requirements, mainly for automotive use. Components which have not been so designated are neither designed nor intended for automotive use; and TI will not be responsible for any failure of such components to meet such requirements. Products Applications Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers DLP® Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps DSP dsp.ti.com Energy and Lighting www.ti.com/energy Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial Interface interface.ti.com Medical www.ti.com/medical Logic logic.ti.com Security www.ti.com/security Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video RFID www.ti-rfid.com OMAP Mobile Processors www.ti.com/omap TI E2E Community e2e.ti.com Wireless Connectivity www.ti.com/wirelessconnectivity Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright © 2012, Texas Instruments Incorporated