L4971D 1.5A STEP DOWN SWITCHING REGULATOR 1 FEATURES 2 DESCRIPTION L4971. Figure 1. Package

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1 1.A STEP DOWN SWITCHING REGULATOR 1 FEATURES UP TO 1.A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 8V TO V PRECISE 3.3V (±1%) INTERNAL REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM 3.3V TO V SWITCHING FREQUENCY ADJUSTABLE UP TO 3KHz VOLTAGE FEEDFORWARD ZERO LOAD CURRENT OPERATION INTERNAL CURRENT LIMITING (PULSE- BYPULSE AND HICCUP MODE) INHIBIT FOR ZERO CURRENT CONSUMPTION PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN SOFT START FUNCTION DESCRIPTION The L4971 is a step down monolithic power switching regulator delivering 1.A at a voltage between 3.3V and V (selected by a simple external divider). Realized in BCD mixed technology, the device uses an internal power D-MOS transistor (with a typical Rdson of.ω) to obtain very high efficency and high switching speed. Figure 1. Package DIP8 Table 1. Order Codes Part Number L4971 L4971D L4971D13TR SO16W Package DIP8 SO16W SO16 in Tape & Reel A switching frequency up to 3KHz is achievable (the maximum power dissipation of the packages must be observed). A wide input voltage range between 8V to V and output voltages regulated from 3.3V to V cover the majority of today s applications. Features of this new generations of DC-DC converter include pulse-by-pulse current limit, hiccup mode for short circuit protection, voltage feedforward regulation, soft-start, protection against feedback loop disconnection, inhibit for zero current consumption and thermal shutdown. The device is available in plastic dual in line, DIP8 for standard assembly, and SO16W for SMD assembly. Figure 1. Block Diagram Vi=8V to V C 1 µf 63V C 7 nf R 1 K C.7nF 3 L L1 16µH (771) V O =3.3V/1.A C 1nF R 9.1K C 4 nf C 6 1nF D1 STPS 3L6U C 8 33µF D97IN748A May Rev. 11 1/13

2 Figure. Block Diagram VCC SS_INH COMP FB V THERMAL SHUTDOWN INHIBIT E/A OSCILLATOR VOLTAGES MONITOR SOFTSTART PWM INTERNAL INTERNAL 3.3V REFERENCE SUPPLY.1V R S Q DRIVE CBOOT CHARGE CBOOT CHARGE AT LIGHT LOADS 6 BOOT OSC GND OUT D97IN94 Figure 3. Pin Connections N.C N.C. GND 1 N.C. GND SS_INH OSC OUT 1 8 FB COMP BOOT VCC D97IN9 SS_INH OSC OUT OUT N.C. N.C FB COMP BOOT VCC N.C. N.C. DIP8 D97IN96 SO16 Table. Pin Description DIP SO (*) Name Function 1 GND Ground 3 SS_INH A logic signal (active low) disables the device (sleep mode operation). A capacitor connected between this pin and ground determines the soft start time. When this pin is grounded disabled the device (driven by open collector/drain). 3 4 OSC An external resistor connected between the unregulated input voltage and this pin and a capacitor connected from this pin to ground fix the switching frequency. (Line feed forward is automatically obtained) 4, 6 OUT Stepdown regulator output 11 VCC Unregulated DC input voltage 6 1 BOOT A capacitor connected between this pin and OUT allows to drive the internal DMOS Transistor 7 13 COMP E/A output to be used for frequency compensation 8 14 FB Stepdown feedback input. Connecting directly to this pin results in an output voltage of 3.3V. An external resistive divider is required for higher output voltages. (*) Pins 1, 7, 8, 9, 1, 1 and 16 are not internally, electrically connected to the die. /13

3 Table 3. Absolute Maximum Ratings Symbol Minidip S16 Parameter Value Unit V V 11 Input voltage 8 V V4 V,V 6 Output DC voltage -1 V Output peak voltage at t =.1µs f=khz - V I 4 I,I 6 Maximum output current int. limit. V 6 -V V 1 -V V V 6 V 1 Bootstrap voltage 7 V V 7 V 13 Analogs input voltage (V CC = 4V 1 V V V 3 Analogs input voltage (V CC = 4V) 13 V V 8 V 14 (V CC = V) P tot Power dissipation a Tamb 6 C DIP8 1 W SO16.8 W T j,t stg Junction and storage temperature -4 to 1 C V V Table 4. Thermal Data Symbol Parameter DIP8 SO16 Unit R th(j-amb) Thermal Resistance Junction to ambient Max. (*) 11 (*) C/W (*) Package mounted on board. 3 ELECTRICAL CHARACTERISTCS Table. (T j = C, Cosc =.7nF, Rosc = kω, V CC = 4V, unless otherwise specified.) * Specification Refered to T j from to 1 C Symbol Parameter Test Condition Min. Typ. Max. Unit DYNAMIC CHARACTERISTIC V I Operating input voltage range Vo = 3.3 to V; Io = 1.A * 8 V Vo Output voltage Io =.A V Io =. to 1.A V Vcc = 8 to V * V Vd Dropout voltage Vcc = 1V; Io = 1.A.44. V *.88 V I l Maximum limiting current V cc = 8 to V *. 3 A Efficiency Vo = 3.3V; Io = 1.A 8 % fs Switching frequency * 1 11 KHz SVRR Supply voltage ripple rejection Vi = Vcc+V RMS ; Vo = Vref; Io = 1.A; f ripple = 1Hz 6 db Voltage stability of switching frequency Temp. stability of switching frequency Vcc = 8 to V 3 6 % Tj = to 1 C 4 % 3/13

4 Table. (T j = C, Cosc =.7nF, Rosc = kω, V CC = 4V, unless otherwise specified.) * Specification Refered to T j from to 1 C Soft Start Soft start charge current 3 4 µa Soft start discharge current µa Inhibit V LL Low level voltage *.9 V I sll Isource Low level * 1 µa DC Characteristics Iqop Total operating quiescent current 4 6 ma Iq Quiescent current Duty Cycle = ; V FB = 3.8V. 3. ma Iqst-by Total stand-by quiescent V inh <.9V 1 µa current Vcc = V; Vinh<.9V 1 3 µa Error Amplifier V FB Voltage Feedback Input V R L Line regulation Vcc = 8 to V 1 mv Ref. voltage stability vs temperature *.4 mv/ C V oh High level output voltage V FB =.V 1.3 V V ol Low level output voltage V FB = 3.8V.6 V Io source Source output current V comp = 6V; V FB =.V 3 µa Io sink Sink output current V comp = 6V; V FB = 3.8V 3 µa I b Source bias current 3 µa SVRR E/A Supply voltage ripple rejection V comp = V fb ; V cc = 8 to V 6 8 db DC open loop gain R L = 7 db gm Transconductance I comp = -.1 to.1ma V comp = 6V. ms Oscillator Section Ramp Valley V Ramp peak Vcc = 8V.1.3 V Vcc = V V Maximum duty cycle 9 97 % Maximum Frequency Duty Cycle = % ; R osc = 13kΩ, C osc = 8pF 3 khz 4/13

Table 6. Typical Performance (Using Evaluation Board) fsw = 1kHz Output Voltage Output Ripple Efficiency V CC =3V I O = 1.A Line Regulation I o = 1.A V CC = 8 to V Load Regulation V CC =3V I O =.

5 Table 6. Typical Performance (Using Evaluation Board) fsw = 1kHz Output Voltage Output Ripple Efficiency V CC =3V I O = 1.A Line Regulation I o = 1.A V CC = 8 to V Load Regulation V CC =3V I O =. to 1.A 3.3V 1mV 84 (%) 3mV 6mV.1V 1mV 86 (%) 3mV 6mV 1V 1mV 93 (%) 3mV (V CC =1 to V) 4mV Figure 4. Test and valuation board circuit. Vi=8V to V C 1 µf 63V C 7 nf R 1 K C.7nF 3 L L1 16µH (771) V O =3.3V/1.A R 3 C 1nF C 4 nf R 9.1K C 6 1nF D1 ST PS3L6U C 8 33µF R 4 D97IN749A C1=µF/63V EKE C=.7nF C=1nF C6=1nF C7=nF/63V C8=33µF/3V CG Sanyo L1=16µH KoolMu Turns -.mm R1=K R=9.1K D1=STPS3L6U L4971 V O (V) R3(KΩ) R4(KΩ) Figure. PCB and component layout of the figure 4. /13

6 Figure 6. Quiescent drain current vs. input voltage. Figure 9. Line Regulation Iq (ma) KHz R 1 =K C =1.nF D97IN74 V O (V) Tj=1 C D97IN KHz R 1 =K C =.7nF Tj= C 3 1 Tamb= C % DC Hz Vcc(V) V CC (V) Figure 7. Quiescent current vs. junction temperature Iq (ma) 4 3 V CC =3V % DC KHz R 1 =K C =1.nF 1KHz R 1 =K C =.7nF Hz D97IN Tj( C) Figure 1. Line Regulation V O (V) Tj=1 C Tj= C V CC =3V D97IN I O (A) Figure 8. Stand-by drain current vs. input voltage Figure 11. Switching frquency vs. R1 and C Ibias (µa) Vss=GND Tj= C Tj=1 C D97IN V CC (V) fsw (KHz) 1 1.8nF 1.nF.nF 3.3nF.6nF 4.7nF Tamb= C D97IN R1(KΩ) 6/13

7 Figure 1. Switching Frequency vs. input voltage. fsw (KHz) Tj= C D97IN V CC (V) Figure 13. Switching frequency vs. junction temperature. Figure 1. Efficiency vs output voltage. η (%) KHz KHz V CC =3V I O =1.A D97IN V O (V) Figure 16. Efficiency vs. output current. fsw (KHz) D97IN78 η (%) V CC =8V D97IN738 V CC =1V V CC =4V V CC =48V 9 7 fsw=1khz V O =.1V 6-1 Tj( C) Figure 14. Dropout voltage between pin and I O (A) Figure 17. Efficiency vs. output current. V (V) D97IN736 η (%) D97IN739. Tj=1 C V CC =8V.4.3 Tj= C 8 8 V CC =1V V CC =4V..1 Tj=- C V CC =48V fsw=1khz V O =3.36V I O (A) I O (A) 7/13

8 Figure 18. Efficiency vs. output current. Figure 1. Power dissipation vs. Vcc. η (%) 8 V CC =1V V CC =4V V CC =8V D97IN74 Pdiss (mw) 8 V O =.1V fsw=1khz D97IN743 8 V CC =48V 6 I O =1.A I O =1A fsw=khz V O =.1V I O =.A I O (A) V CC (V) Figure 19. Efficiency vs. output current. Figure. Efficiency vs. V O η (%) 8 8 V CC =1V V CC =8V V CC =4V D97IN741 Pdiss (mw) 8 6 V CC =3V fsw=1khz I O =1.A D97IN V CC =48V fsw=khz V O =3.36V I O (A) I O =1A 4 I O =.A V (V) Figure. Efficiency vs. V CC. η (%) 8 V =.1V-f SW =1KHz V =.1V-f SW =KHz D97IN74 Figure 3. Pulse by pulse limiting current vs. junction temperature. Ilim (A).9.8 fsw=1khz V CC =3V D97IN747 8 V =3.36V-f SW =1KHz V =3.36V-f SW =KHz I O =1.A V CC (V) Tj( C) 8/13

9 Figure 4. Load transient. Figure 7. Soft start capacitor selection vs. Inductor and Vccmax L (µh) fsw=khz D97IN746 6nF 3 47nF 33nF 1 nf V CC max(v) Figure. Line transient. V CC (V) 3 D97IN786 Figure 8. Open loop frequency and phase of error amplifier GAIN (db) D97IN787 Phase GAIN 1 1 1ms/DIV I O = 1A f sw = 1KHz V O (mv) Phase f(hz) 4 13 Figure 6. Soft start capacitor selection Vs inductor and Vccmax. L (µh) 4 fsw=1khz 68nF D97IN74 47nF 3 33nF nf 1 1nF V CCmax (V) 9/13

10 Figure 9. DIP8 Mechanical Data & Package Dimensions mm inch DIM. MIN. TYP. MAX. MIN. TYP. MAX. A OUTLINE AND MECHANICAL DATA a1.1. B b b D E e.4.1 e e F I.8. L Z 1..6 DIP-8 1/13

11 Figure 3. SO16 Mechanical Data & Package Dimensions mm inch DIM. MIN. TYP. MAX. MIN. TYP. MAX. A OUTLINE AND MECHANICAL DATA A B C D (1) E e 1.7. H h L k (min.), 8 (max.) ddd.1.4 (1) D dimension does not include mold flash, protusions or gate burrs. Mold flash, protusions or gate burrs shall not exceed.1mm per side. SO16 (Wide) 161 C 11/13

12 4 REVISION HISTORY Table 7. Revision History Date Revision Description of Changes October 4 1 First Issue in EDOCS May 11 Updated the Layout look & feel. Changed name of the D1 on the figs. 1 and 4. 1/13

13 Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics. All other names are the property of their respective owners STMicroelectronics - All rights reserved STMicroelectronics group of companies Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan - Malaysia - Malta - Morocco - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America 13/13

14 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: STMicroelectronics: L4971D L4971 L4971D13TR E-L4971D13TR E-L4971D E-L4971

L4971D 1.5A STEP DOWN SWITCHING REGULATOR 1 FEATURES 2 DESCRIPTION L4971. Figure 1. Package

L4971D 1.5A STEP DOWN SWITCHING REGULATOR 1 FEATURES 2 DESCRIPTION L4971. Figure 1. Package 1.5A STEP DOWN SWITCHING REGULATOR 1 FEATURES UP TO 1.5A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 8V TO 55V PRECISE 3.3V (±1%) INTERNAL REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM 3.3V TO