L5972D 2A switch step down switching regulator Features ■ 2A internal switch ■ Operating input voltage from 4.4V to 36V ■ Output voltage adjustable from 1.235V to 35V ■ Low dropout operation: 100% duty cycle ■ 250kHz Internally fixed frequency ■ Voltage feedforward Description ■ Zero load current operation ■ Internal current limiting ■ Protection against feedback disconnection ■ Thermal shutdown The L5972D is a step down monolithic power switching regulator with a minimum switch current limit of 2A so it is able to deliver more than 1.5A DC current to the load depending on the application conditions. SO8 The output voltage can be set from 1.235V to 35V. Applications ■ Consumer: STB, DVD, TV, VCR, car radio, LCD monitors ■ Networking: XDSL, modems, DC-DC modules The device uses an internal P-Channel D-MOS transistor (with a typical Rdson of 250mΩ) as switching element to minimize the size of the external components. ■ Computer: printers, audio/graphic cards, optical storage, hard disk drive An internal oscillator fixes the switching frequency at 250kHz. ■ Industrial: changers, car battery, DC-DC converters Having a minimum input voltage of 4.4V only, it is particularly suitable for 5V bus, available in all computer related applications. Figure 1. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection. Test application circuit VIN = 4.4V to 35V C1 10µF 35V CERAMIC VCC COMP OUT 4 2 3 L1 33µH D1 STPS2L40U L5972D 6 C4 22nF C3 220pF 1 8 7 VOUT=3.3V R1 5.6K 5 FB GND R3 4.7K C2 100µF 10V R2 3.3K D03IN1436 October 2007 Rev 10 1/15 www.st.com 15 Contents L5972D 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6 Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 8 Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2/15 L5972D Pin settings 1 Pin settings 1.1 Pin connection Figure 2. Pin connection (top view) OUT 1 8 VCC GND 2 7 GND GND 3 6 GND COMP 4 5 FB D02IN1367 1.2 Pin description Table 1. Pin description N° Pin Description 1 OUT Regulator output. 2,3,6,7 GND Ground. 4 COMP 5 FB 8 VCC E/A output for frequency compensation. Feedback input. Connecting directly to this pin results in an output voltage of 1.23V. An external resistive divider is required for higher output voltages. Unregulated DC input voltage. 3/15 Electrical data L5972D 2 Electrical data 2.1 Maximum ratings Table 2. Absolute maximum ratings Symbol Unit 40 V V V Input voltage V1 Out pin DC voltage Out pin peak voltage at ∆t = 0.1µs -1 to 40 -5 to 40 I1 Maximum output current int. limit. Ptot Tj Tstg Analog pins 4 V 1.2 W Operating junction temperature range -40 to 150 °C Storage temperature range -55 to 150 °C SO8 Unit (1) °C/W Power dissipation at TA ≤ 70°C Thermal data Table 3. Thermal data Symbol RthJA Parameter Maximum thermal resistance junction-ambient 1. Package mounted on board 4/15 Value V8 V4, V5 2.2 Parameter 65 L5972D 3 Electrical characteristics Electrical characteristics Table 4. Electrical characteristics ( TJ = 25°C, VCC = 12V, unless otherwise specified) Symbol VCC RDS(on) Parameter Operating input voltage range Test condition Vo = 1.235V; Io = 2A Mosfet on Resistance Il Maximum limiting current fs Switching frequency Min (1) Max Unit 36 V 0.250 0.5 Ω 2 2.5 3 A 212 250 280 kHz 225 250 275 kHz 100 % 4.4 (1) VCC = 4.4V to 36V (1) Duty cycle Typ 0 Dynamic characteristics (see test circuit ). V5 Voltage feedback h Efficiency 4.4V < VCC < 36V, 20mA < IO < 2A (1) 1.220 1.235 1.25 V 1.198 1.235 1.272 V VO = 5V, VCC = 12V 90 % DC characteristics Iqop Total operating quiescent current Iq Quiescent current Duty cycle = 0; VFB = 1.5V VOH High level output voltage VFB = 1V VOL Low level output voltage VFB = 1.5V Source output current VCOMP = 1.9V; VFB = 1V 200 300 µA Io sink Sink output current VCOMP = 1.9V; VFB = 1.5V 1 1.5 mA Ib Source bias current (1) 3 5 mA 2.5 mA Error amplfier Io source gm 3.5 V 0.4 2.5 DC open loop gain RL = ∞ Transconductance Icomp = -0.1mA to 0.1mA VCOMP = 1.9V 50 4 V µA 65 dB 2.3 mS 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. 5/15 Typical characteristics 4 L5972D Typical characteristics Figure 3. Vo (V) 3.312 Output voltage vs. junction temperature Figure 4. Quiescent current vs. junction temperature Iq (mA) 2 Vcc = 12V Vo = 3.3V 3.308 3.304 1.8 Tj = 25°C 3.3 3.296 1.6 3.292 3.288 1.4 3.284 Vcc = 12V DC = 0% Tj = 125°C 3.28 1.2 3.276 0 0.5 1 -50 1.5 0 Io (A) Figure 5. Line regulator Figure 6. Vcc = 12V Vo = 3.3V 3.304 100 150 Shutdown current vs. junction temperature Ishd (µA) 70 Vo (V) 3.312 3.308 50 Tj (°C) Tj = 25°C 60 Vcc = 12V 3.3 3.296 50 3.292 Tj = 125°C 3.288 40 3.284 3.28 30 3.276 0 Figure 7. 10 20 Vcc (V) 30 40 Output voltage vs. junction temperature -50 Figure 8. 0 50 Tj (°C) 100 150 Switching frequency vs. junction temperature Iq (mA) Vo (V) 1.25 2 1.24 1.8 1.23 1.6 1.22 Vcc = 12V 1.21 1.4 Vcc=12V 1.2 1.2 -50 6/15 Vcc = 12V DC = 0% 0 50 Tj (°C) 100 150 -50 0 50 Tj (°C) 100 150 L5972D 5 Application circuit Application circuit In figure 8 is shown the demo board application circuit for the device in SMD version, where the input supply voltage, Vcc, can range from 4.4V to 25V due to the rated voltage of the input capacitor and the output voltage is adjustable from 1.235V to Vcc. Figure 9. Demo board application circuit VCC VIN = 4.4V to 25V COMP C1 10µF 25V CERAMIC D1 STPS2L25U 4 2 3 L1 33µH OUT L5972D 6 C4 22nF C3 220pF 1 8 7 VOUT=3.3V R1 5.6K 5 FB GND C2 100µF 10V R2 3.3K R3 4.7K D03IN1438 Table 5. Component list Reference Part number Description Manufacturer C1 GRM32DR61E106KA12L 10µF, 25V MURATA C2 POSCAP 10TPB100M 100µF, 10V Sanyo C3 C1206C221J5GAC 220pF, 5%, 50V KEMET C4 C1206C223K5RAC 22nF, 10%, 50V KEMET R1 5.6K, 1%, 0.1W 0603 Neohm R2 3.3K, 1%, 0.1W 0603 Neohm R3 4.7K, 1%, 0.1W 0603 Neohm D1 STPS2L25U 2A, 25V ST L1 DO3316P-333 33µH, 2.1A COILCRAFT 7/15 Application circuit L5972D Figure 10. PCB layout (component side) Figure 11. PCB layout (bottom side) Figure 12. PCB layout (front side) Sideways two graphs show the TJ versus output current in different conditions of the input and output voltage. 8/15 L5972D Application circuit Figure 13. Junction temperature vs output current Figure 14. Efficiency vs output current 95 TJ(°C) 93 100.0 Vo=3.3V 91 Vo=2.5V Vin=5V Tamb.=25 °C 80.0 89 Vo=3.3V 87 70.0 Efficiency (%) 90.0 Vo=1.8V 60.0 50.0 85 Vo=2.5V 83 81 79 Vo=1.8V 77 75 40.0 73 Vin=5V 71 30.0 69 20.0 67 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0.1 0.3 0.5 0.7 Io(A) 1.1 1.3 1.5 1.7 Io (A) Figure 15. Junction temperature vs output current Figure 16. Efficiency vs output current TJ(°C) 96 100.0 94 92 90.0 Vo=5V Vin=12V Tamb= 25°C Vo=5V 90 Vo=3.3V 88 Efficiency (%) 80.0 0.9 70.0 60.0 Vo=2.5V 50.0 Vo=3.3V 86 84 82 80 Vo=2.5V 78 76 40.0 74 Vin=12V 72 30.0 70 20.0 0.1 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 Io (A) Io(A) 9/15 Application ideas 6 L5972D Application ideas Figure 17. Positive buck-boost regulator 8 L5972D 6 2 C3 22nF R3 4.7k D1 STPS2L25U FB 4 C2 220pF D2 STPS2L25U VOUT=12V/0.45A 1 COMP C1 10uF 10V Ceramic L1 33uH OUT Vcc VIN=5V 24k 5 3 7 C4 100uF 16V M1 STN4NE03L GND 2.7k Figure 18. Buck-boost regulator VIN=5V 8 1 COMP C2 10uF C3 25V Ceramic 220pF C1 10uF 10V Ceramic L1 33uH OUT Vcc L5972D FB 4 2 6 C4 22nF R3 4.7k 7 5 3 D1 STPS2L25U 2.7k GND 24k VOUT=-12V/0.45A C5 100uF 16V Figure 19. Dual output voltage with auxiliary winding n=N1/N2=2 D2 N2 STPS2L25U VIN=12V OUT Vcc 8 1 L5972D COMP C1 10uF 25V 10/15 4 2 C2 220pF C3 22nF R3 4.7k VOUT1=5V 50mA 6 7 GND 5 3 N1 D1 STPS2L25U VOUT=3.3V FB C4 100uF 10V C5 47uF 10V L5972D 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 11/15 Package mechanical data Table 6. L5972D SO-8 Mechanical data mm. inch Dim. Min Typ Max Min Typ Max A 1.35 1.75 0.053 0.069 A1 0.10 0.25 0.004 0.010 A2 1.10 1.65 0.043 0.065 B 0.33 0.51 0.013 0.020 C 0.19 0.25 0.007 0.010 D (1) 4.80 5.00 0.189 0.197 E 3.80 4.00 0.15 0.157 e 1.27 0.050 H 5.80 6.20 0.228 0.244 h 0.25 0.50 0.010 0.020 L 0.40 1.27 0.016 0.050 k ddd 0° (min.), 8° (max.) 0.10 0.004 1. Dimensions D does not include mold flash, protru-sions or gate burrs. Mold flash, potrusions or gate burrs shall not exceed 0.15mm (.006inch) in total (both side). Figure 20. Package dimensions 12/15 L5972D 8 Order codes Order codes Table 7. Order codes Part number Package Packaging L5972D SO8 Tube L5972D013TR SO8 Tape and reel 13/15 Revision history 9 L5972D Revision history Table 8. 14/15 Revision history Date Revision Changes 02-Feb-2007 8 Updated Table 5 on page 7 10-Apr-2007 9 Mechanical data typo 16-Oct-2007 10 Updated Section 5: Application circuit on page 7 L5972D 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. All ST products are sold pursuant to ST’s terms and conditions of sale. Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no liability whatsoever relating to the choice, selection or use of the ST products and services described herein. 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