L5972D 2A SWITCH STEP DOWN SWITCHING REGULATOR ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 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 ZERO LOAD CURRENT OPERATION INTERNAL CURRENT LIMITING PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN SO8 (4+2+2) ORDERING NUMBERS: L5972D (SO8) L5972D013TR (Tape & Reel) DESCRIPTION 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. The output voltage can be set from 1.235V to 35V. 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. 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: CHARGERS, CAR BATTERY DC-DC CONVERTERS An internal oscillator fixes the switching frequency at 250KHz. Having a minimum input voltage of 4.4V only, it is particularly suitable for 5V 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. 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 May 2003 1/10 L5972D PIN CONNECTION OUT 1 8 VCC GND 2 7 GND GND 3 6 GND COMP 4 5 FB D02IN1367 PIN DESCRIPTION N° Pin Function 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. THERMAL DATA Symbol Rth (j-amb) Parameter Thermal Resistance Junction to ambient (*) Package mounted on board (4cm2 Max. Value Unit 65 (*) °C/W Value Unit 40 V V V ground-plane) ABSOLUTE MAXIMUM RATINGS Symbol V8 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. V4, V5 Ptot Tj Tstg 2/10 Parameter Analog pins 4 V 1.2 W Operating junction temperature range -40 to 150 °C Storage temperature range -55 to 150 °C Power dissipation at Tamb ≤ 70°C L5972D ELECTRICAL CHARACTERISTICS (Tj = 25°C, VCC = 12V, unless otherwise specified.) (*) Specification Referred to Tj from -40 to 125°C. Symbol Parameter Test Condition Min. Typ. Max. Unit 36 V 0.375 0.75 V Operating input voltage range Vo = 1.235V; Io = 1.5A * Dropout voltage VCC = 4.4V; Io = 1.5A * Il Maximum limiting current VCC = 4.4V to 36V * 2 2.5 3 A fs Switching frequency * 212 250 280 KHz 225 250 275 KHz 100 % VCC Vd Duty cycle 4.4 0 DYNAMIC CHARACTERISTICS (see test circuit ). V5 h Voltage feedback Efficiency 4.4V < VCC < 36V, 20mA < IO < 1.5A * 1.220 1.235 1.25 V 1.198 1.235 1.272 V VO = 5V, VCC = 12V 90 % DC CHARACTERISTICS Iqop Iq Total operating quiescent current Quiescent current * 3 Duty Cycle = 0; VFB = 1.5V 5 mA 2.5 mA ERROR AMPLIFIER VOH High level output voltage VFB = 1V VOL Low level output voltage VFB = 1.5V Source output current VCOMP = 1.9V; VFB = 1V Io sink Sink output current VCOMP = 1.9V; VFB = 1.5V Ib Source bias current Io source gm 3.5 V 0.4 200 300 µA 1 1.5 mA 2.5 DC open loop gain RL = ∞ Transconductance Icomp = -0.1mA to 0.1mA VCOMP = 1.9V V 50 4 µA 65 dB 2.3 mS 3/10 L5972D Figure 4. Quiescent Current vs. Junction Figure 1. Output Voltage vs. Junction Temperature Iq (mA) Vo (V) 3.312 2 Vcc = 12V Vo = 3.3V 3.308 1.8 3.304 Tj = 25°C 3.3 1.6 3.296 3.292 1.4 3.288 3.284 Vcc = 12V DC = 0% Tj = 125°C 1.2 3.28 -50 3.276 0 0.5 1 0 1.5 50 Tj (°C) 100 150 Io (A) Figure 5. Shutdown Current vs.Junction Temperature Figure 2. Line Regulation Vo (V) Ishd (µA) 70 3.312 Vcc = 12V Vo = 3.3V 3.308 3.304 Tj = 25°C 60 3.3 Vcc = 12V 3.296 3.292 50 Tj = 125°C 3.288 3.284 40 3.28 3.276 0 10 20 Vcc (V) 30 40 30 -50 Figure 3. Output Voltage vs. Junction Temperature 0 50 Tj (°C) 100 150 Figure 6. Switching Frequency vs.Junction Temperature Vo (V) 1.25 Iq (mA) 2 1.24 1.8 1.23 1.6 1.22 Vcc = 12V 1.21 Vcc=12V 1.4 Vcc = 12V DC = 0% 1.2 -50 4/10 0 50 Tj (°C) 100 150 1.2 -50 0 50 Tj (°C) 100 150 L5972D APPLICATION CIRCUIT In figure 7 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 7. Demo board Application Circuit VIN = 4.4V to 25V C1 10µF 25V CERAMIC VCC COMP C3 220pF 4 2 3 VOUT=3.3V D1 STPS2L25U L5972D 6 C4 22nF L1 33µH OUT 1 8 7 R1 5.6K 5 FB GND C2 100µF 10V R2 3.3K R3 4.7K D03IN1438 Table 1. Component List Reference Part Number C1 Description Manufacturer 10µF, 25V TOKIN 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 5/10 L5972D Figure 8. PCB layout (component side) 42mm 34mm Figure 9. PCB layout (bottom side) Figure 10. PCB layout (front side) Sideways two graphs show the Tj versus output current in different conditions of the input and output voltage. 6/10 L5972D Figure 13. Efficiency vs. Output Current Figure 11. Junction Temperature vs. Output Current TJ(°C) 95 100.0 93 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 30.0 Vcc=5V 71 69 20.0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 67 2 0.1 0.3 0.5 0.7 Io(A) 0.9 1.1 1.3 1.5 1.7 Io (A) Figure 12. Junction Temperature vs. Output Current Figure 14. Efficiency vs. Output Current TJ(°C) 96 100.0 94 92 90.0 Vin=12V Tamb= 25°C Vo=3.3V Vo=5V 90 88 Efficiency (%) 80.0 Vo=5V 70.0 60.0 Vo=2.5V 50.0 Vo=3.3V 86 84 82 80 Vo=2.5V 78 76 40.0 74 30.0 Vin=12V 72 70 20.0 0.2 0.4 0.6 0.8 1 1.2 Io(A) 1.4 1.6 1.8 2 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 Io (A) 7/10 L5972D APPLICATION IDEAS Figure 15. Positive Buck-Boost regulator 8 L5972D 2 6 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 16. Buck-Boost regulator 8 1 COMP C1 10uF 10V Ceramic C2 10uF C3 25V Ceramic 220pF L1 33uH OUT Vcc VIN=5V 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 17. Dual output voltage with auxiliary winding n=N1/N2=2 D2 N2 STPS2L25U VIN=12V OUT Vcc 8 1 L5972D COMP C1 10uF 25V 8/10 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 mm DIM. MIN. TYP. A a1 inch MAX. MIN. TYP. 1.75 0.1 0.25 a2 MAX. 0.069 0.004 0.010 1.65 0.065 a3 0.65 0.85 0.026 0.033 b 0.35 0.48 0.014 0.019 b1 0.19 0.25 0.007 0.010 C 0.25 0.5 0.010 0.020 c1 45° (typ.) D (1) 4.8 5.0 0.189 0.197 E 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 3.81 0.150 F (1) 3.8 4.0 0.15 0.157 L 0.4 1.27 0.016 0.050 M S OUTLINE AND MECHANICAL DATA 0.6 0.024 SO8 8 ° (max.) (1) D and F do not include mold flash or protrusions. Mold flash or potrusions shall not exceed 0.15mm (.006inch). 9/10 L5972D Information furnished is believed to be accurate and reliable. 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