L5973D 2.5 A switch step down switching regulator Features ■ 2.5 A internal switch ■ Operating input voltage from 4 V to 36 V ■ 3.3 V / (±2%) reference voltage ■ Output voltage adjustable from 1.235 V to 35 V ■ Low dropout operation: 100 % duty cycle ■ 250 kHz internally fixed frequency Description ■ Voltage feedforward ■ Zero load current operation ■ Internal current limiting ■ Inhibit for zero current consumption ■ Synchronization ■ Protection against feedback disconnection ■ Thermal shutdown The L5973D is a step down monolithic power switching regulator with a minimum switch current limit of 2.5 A so it is able to deliver more than 2 A DC current to the load depending on the application conditions. The output voltage can be set from 1.235 V to 35 V. The high current level is also achieved thanks to an SO8 package with exposed frame, that allows to reduce the Rth(j-amb) down to approximately 40 °C/W. The device uses an internal P-channel D-MOS transistor (with a typical Rdson of 250 mΩ) as switching element to minimize the size of the external components. An internal oscillator fixes the switching frequency at 250 kHz. Having a minimum input voltage of 4 V only, it is particularly suitable for 5 V bus, available in all computer related applications. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection. HSOP8 exposed pad Applications ■ Consumer: STB, DVD, TV, VCR, car radio, LCD monitors ■ Networking: XDSL, modems, DC-DC modules ■ Computer: printers, audio/graphic cards, optical storage, hard disk drive ■ Industrial: changers, car battery, DC-DC converters Figure 1. Test application circuit VREF 3.3V VCC VIN = 4.4V to 35V SYNC. C1 10µF 35V CERAMIC COMP C4 22nF C3 220pF 6 1 8 OUT D1 STPS340U L5973D 2 3 4 INH L1 15µH VOUT=3.3V R1 5.6K 5 7 FB GND R3 4.7K C2 330µF 10V R2 3.3K D03IN1439 January 2008 Rev 16 1/17 www.st.com 17 Contents L5973D Contents 1 2 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6 Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 8 Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2/17 L5973D Pin settings 1 Pin settings 1.1 Pin connection Figure 2. Pin connection (top view) OUT 1 8 VCC SYNC 2 7 GND INH 3 6 VREF COMP 4 5 FB D98IN955 1.2 Pin description Table 1. Pin description N° Type Description 1 OUT 2 SYNC 3 INH 4 COMP 5 FB 6 VREF 3.3 V VREF. No cap is requested for stability. 7 GND Ground. 8 VCC Unregulated DC input voltage. Regulator output. Master/slave synchronization. A logical signal (active high) disables the device. If INH not used the pin must be grounded. When it is open an internal pull-up disable the device. E/A output for frequency compensation. Feedback input. Connecting directly to this pin results in an output voltage of 1.23 V. An external resistive divider is required for higher output voltages. 3/17 Electrical data L5973D 2 Electrical data 2.1 Maximum ratings Table 2. Absolute maximum ratings Symbol Unit 40 V V V Input voltage V1 Output DC voltage Output peak voltage at t = 0.1 µs -1 to 40 -5 to 40 I1 Maximum output current int. limit. Analog pins V3 INH V2 SYNC PTOT TJ TSTG 4 V -0.3 V to VCC -0.3 to 4 V 2.25 W Operating junction temperature range -40 to 150 °C Storage temperature range -55 to 150 °C Power dissipation at TA ≤ 60 °C Thermal data Table 3. Thermal data Symbol RthJA Parameter Maximum thermal resistance junction-ambient 1. Package mounted on board 4/17 Value V8 V4, V5 2.2 Parameter HSOP8 Exposed Pad 40 (1) Unit °C/W L5973D 3 Electrical characteristics Electrical characteristics Table 4. Electrical characteristics ( TJ = 25 °C, VCC = 12 V, unless otherwise specified) Symbol VCC RDS(on) Parameter Operating input voltage range Test condition Vo = 1.235 V; Io = 2 A Mosfet on Resistance Il Maximum limiting current fs Switching frequency Min (1) Max Unit 36 V 0.250 0.5 Ω 2.5 3 3.5 A 212 250 280 kHz 225 250 275 kHz 100 % 4 (1) VCC = 4.4 V to 36 V (1) Duty cycle Typ 0 Dynamic characteristics (see test circuit ). V5 Voltage feedback h Efficiency 4.4 V < VCC < 36 V, 20 mA < IO < 2 A (1) 1.220 1.235 1.25 V 1.198 1.235 1.272 V VO = 5 V, VCC = 12 V 90 % DC characteristics Iqop Total operating quiescent current Iq Quiescent current Iqst-by Total stand-by quiescent current (1) 3 Duty Cycle = 0; VFB = 1.5 V 5 mA 2.5 mA Vinh > 2.2 V (1) 50 100 µA VCC = 36 V; Vinh > 2.2 V (1) 80 150 µA 0.8 V Inhibit INH threshold voltage Device ON Device OFF 2.2 V 3.5 V Error amplfier VOH High level output voltage VFB = 1 V VOL Low level output voltage VFB = 1.5 V Source output current VCOMP = 1.9 V; VFB = 1 V 200 300 µA Sink output current VCOMP = 1.9 V; VFB = 1.5 V 1 1.5 mA Io source Io sink 0.4 V 5/17 Electrical characteristics Table 4. L5973D Electrical characteristics (continued) ( TJ = 25 °C, VCC = 12 V, unless otherwise specified) Symbol Ib gm Parameter Test condition Min Source bias current DC open loop gain RL = ∞ Transconductance Icomp = -0.1 mA to 0.1 mA VCOMP = 1.9 V High input voltage VCC = 4.4 V to 36 V Low input voltage VCC = 4.4 V to 36 V 50 Typ Max Unit 2.5 4 µA 57 dB 2.3 mS Sync function 2.5 (2) 0.11 0.21 VREF V 0.74 V 0.25 0.45 mA mA Slave sink current Vsync = 0.74 V Vsync = 2.33 V Master output amplitude Isource = 3 mA 2.75 3 V Output pulse width no load, Vsync = 1.65 V 0.20 0.35 µs 3.234 3.3 3.366 V 3.2 3.3 3.399 V Reference section Reference voltage IREF = 0 to 5 mA VCC = 4.4 V to 36 V (1) Line regulation IREF = 0 mA VCC = 4.4 V to 36 V 5 10 mV Load regulation IREF = 0 to 5 mA 8 15 mV 18 30 mA Short circuit current 10 1. Specification Referred to TJ from -40 to 125 °C. Specification over the -40 to +125 TJ Temperature range are assured by design, characterization and statistical correlation. 2. Guaranteed by design. 6/17 L5973D 4 Typical characteristics Typical characteristics Figure 3. Line regulation Figure 4. Vo (V) Ishd (µA) 70 3.312 Vcc = 12V Vo = 3.3V 3.308 3.304 Shutdown current vs junction temperature Tj = 25°C 60 3.3 Vcc = 12V 3.296 50 3.292 Tj = 125°C 3.288 40 3.284 3.28 3.276 30 0 Figure 5. 10 20 Vcc (V) 30 40 Output voltage vs junction temperature -50 Figure 6. Vo (V) 1.25 50 Tj (°C) 0 100 150 Switching frequency vs junction temperature Fsw (KHz) 260 1.24 250 1.23 240 1.22 Vcc = 12V 1.21 230 Vcc=12V 220 1.2 -50 Figure 7. Vcc = 12V Vo = 3.3V 0 50 Tj (°C) 100 150 -50 0 50 Tj (°C) 100 150 Quiescent current vs junction temperature Iq (mA) 2 1.8 1.6 1.4 Vcc = 12V DC = 0% 1.2 -50 0 50 Tj (°C) 100 150 7/17 Typical characteristics Figure 8. L5973D Junction temperature vs output current Tj(°C) 120 110 Vin=5V 100 Tamb=25°C 90 80 70 60 50 40 30 20 0.2 0.4 0.6 0.8 1 Figure 9. Junction temperature vs output current Tj (°C) 120 Vo=3.3V Vo=2.5V 110 100 Vo=5V Vin=12V Tamb=25°C 90 Vo=1.8V 80 Vo=2.5V 70 60 50 40 30 20 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Io(A) Vo=1.8V Vin=5V 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 Io (A) 8/17 2.2 2.4 2.6 Figure 11. Efficiency vs output current Vo=3.3V Vo=2.5V 2 Io (A) Efficiency (%) Efficiency (%) Figure 10. Efficiency vs output current 95 93 91 89 87 85 83 81 79 77 75 73 71 69 67 Vo=3.3V 91 89 87 85 83 81 79 77 75 73 71 69 67 65 Vo=5V Vo=3.3V Vo=2.5V Vin=12V 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 Io (A) L5973D 5 Application circuit Application circuit In figure 6 is shown the demonstration board application circuit, where the input supply voltage, VCC, can range from 4 V to 25 V due to the rated voltage of the input capacitor and the output voltage is adjustable from 1.235 V to VCC. Figure 12. Demonstration board application circuit VREF 3.3V VCC VIN = 4.4V to 25V SYNC. COMP C1 10µF 25V CERAMIC C4 22nF C3 220pF 6 1 8 D1 STPS2L25U L5973D 2 3 4 INH 7 L1 15µH OUT VOUT=3.3V R1 5.6K C2 330µF 6.3V 5 FB GND R2 3.3K R3 4.7K D03IN1440 Table 5. Component list Reference Part number Description Manufacturer C1 GRM32DR61E106KA12L 10 µF, 25 V Murata C2 POSCAP 6TPB330M 330 µF, 6.3 V Sanyo C3 C1206C221J5GAC 220 pF, 5%, 50 V KEMET C4 C1206C223K5RAC 22 nF, 10%, 50 V KEMET R1 5.6 K, 1%, 0.1 W 0603 Neohm R2 3.3 K, 1%, 0.1 W 0603 Neohm R3 4.7 K, 1%, 0.1 W 0603 Neohm D1 STPS2L25U 2 A, 25 V ST L1 DO3316P-153 15 µH, 3 A COILCRAFT 9/17 Application circuit L5973D Figure 13. PCB layout (component side) Figure 14. PCB layout (bottom side) Figure 15. PCB layout (front side) Below some graphs show the TJ versus output current in different conditions of the input and output voltage and some efficiency measurements. 10/17 L5973D 6 Application ideas Application ideas Figure 16. Positive buck-boost regulator Figure 17. Buck-boost regulator Figure 18. Dual output voltage with auxiliary winding 11/17 Application ideas L5973D When an output voltage below the internal reference (1.235 V) is required, the circuit reported in the figure 18 can been used. In this case the minimum voltage reachable is 0.6 V and can be easily calculated with the following formula: VOUT = VFB - [(VREF - VFB)x(R2 / R1)] If the load is not present, a resistor connected between VOUT and GND is required in order to avoid that the voltage across COUT increases. The value of this resistor has to be calculated taking into account that the current flowing through this resistance has to be higher than the current flowing through R2. Figure 19. Output voltage below the 1.235 V internal voltage reference 12/17 L5973D 7 Package mechanical data Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect . The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com 13/17 Package mechanical data Table 6. L5973D HSOP8 mechanical data mm inch Dim Min Typ A Min Typ 1.70 Max 0.0669 A1 0.00 A2 1.25 b 0.31 0.51 0.0122 0.0201 c 0.17 0.25 0.0067 0.0098 D 4.80 4.90 5.00 0.1890 0.1929 0.1969 D1 3 3.1 3.2 0.118 0.122 0.126 E 5.80 6.00 6.20 0.2283 0.2441 E1 3.80 3.90 4.00 0.1496 0.1575 E2 2.31 2.41 2.51 0.091 e 0.10 0.00 0.0039 0.0492 0.095 0.099 1.27 h 0.25 0.50 0.0098 0.0197 L 0.40 1.27 0.0157 0.0500 k ccc Figure 20. Package dimensions 14/17 Max 0° (min), 8° (max) 0.10 0.0039 L5973D 8 Order code Order code Table 7. Order code Part number Package Packaging L5973D HSOP8 (Exposed pad) Tube L5973D013TR HSOP8 (Exposed pad) Tape and reel 15/17 Revision history 9 L5973D Revision history pp Table 8. 16/17 Revision history Date Revision Changes 01-Nov-2005 10 Updated package information 22-May-2006 11 Electrical characteristic Table 4 updated, new application idea Figure 19 added, new template 13-Nov-2006 12 Typo in order codes 26-Jan-2007 13 Updated Table 4 on page 5 17-Oct-2007 14 Updated Section 5: Application circuit on page 9 24-Oct-2007 15 Updated Table 6 on page 14 07-Jan-2008 16 Updated Table 6 on page 14 L5973D Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. 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