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L5972D
2A SWITCH STEP DOWN SWITCHING REGULATOR
s s s s s s s s s s
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 250m) as switching element to minimize the size of the external components. 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.
APPLICATIONS: s CONSUMER: STB, DVD, TV, VCR,CAR RADIO, LCD MONITORS s NETWORKING: XDSL, MODEMS,DC-DC MODULES s COMPUTER: PRINTERS, AUDIO/GRAPHIC CARDS, OPTICAL STORAGE, HARD DISK DRIVE s INDUSTRIAL: CHARGERS, CAR BATTERY DC-DC CONVERTERS
TEST APPLICATION CIRCUIT
VIN = 4.4V to 35V VCC OUT L1 33H D1 STPS2L40U 7 5 FB GND R3 4.7K R2 3.3K VOUT=3.3V
8
1
C1 10F 35V CERAMIC
COMP C4 22nF C3 220pF
L5972D
4 6 2 3
R1 5.6K
C2 100F 10V
D03IN1436
May 2003
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L5972D
PIN CONNECTION
OUT GND GND COMP
1 2 3 4
D02IN1367
8 7 6 5
VCC GND GND FB
PIN DESCRIPTION
N 1 2,3,6,7 4 5 8 Pin OUT GND COMP FB VCC Regulator Output. Ground. 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. Function
THERMAL DATA
Symbol Rth (j-amb) Parameter Thermal Resistance Junction to ambient
(4cm2 ground-plane)
Value Max. 65 (*)
Unit C/W
(*) Package mounted on board
ABSOLUTE MAXIMUM RATINGS
Symbol V8 V1 I1 V4, V5 Ptot Tj Tstg Input Voltage Out pin DC voltage Out pin peak voltage at t = 0.1s Maximum output current Analog pins Power dissipation at Tamb 70C Operating junction temperature range Storage temperature range Parameter Value 40 -1 to 40 -5 to 40 int. limit. 4 1.2 -40 to 150 -55 to 150 V W C C Unit V V V
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L5972D
ELECTRICAL CHARACTERISTICS (Tj = 25C, VCC = 12V, unless otherwise specified.) (*) Specification Referred to Tj from -40 to 125C.
Symbol VCC Vd Il fs Parameter Operating input voltage range Dropout voltage Maximum limiting current Switching frequency Test Condition Vo = 1.235V; Io = 1.5A VCC = 4.4V; Io = 1.5A VCC = 4.4V to 36V * * * * 2 212 225 Duty cycle DYNAMIC CHARACTERISTICS (see test circuit ). V5 Voltage feedback 4.4V < VCC < 36V, 20mA < IO < 1.5A VO = 5V, VCC = 12V 1.220 * 1.198 1.235 1.235 90 1.25 1.272 V V % 0 Min. 4.4 0.375 2.5 250 250 Typ. Max. 36 0.75 3 280 275 100 Unit V V A KHz KHz %
h
Efficiency
DC CHARACTERISTICS Iqop Iq Total operating quiescent current Quiescent current Duty Cycle = 0; VFB = 1.5V * 3 5 2.5 mA mA
ERROR AMPLIFIER VOH VOL Io source Io sink Ib High level output voltage Low level output voltage Source output current Sink output current Source bias current DC open loop gain gm Transconductance RL = Icomp = -0.1mA to 0.1mA VCOMP = 1.9V 50 VFB = 1V VFB = 1.5V VCOMP = 1.9V; VFB = 1V VCOMP = 1.9V; VFB = 1.5V 200 1 300 1.5 2.5 65 2.3 4 3.5 0.4 V V A mA A dB mS
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L5972D
Figure 1. Output Voltage vs. Junction Temperature
Vo (V) 3.312 3.308 3.304 3.3 3.296 3.292 3.288 3.284 3.28 3.276 0 0.5 Io (A) 1 1.5 Tj = 125C
1.2 -50 0 50 Tj (C) 100 150 1.4
Figure 4. Quiescent Current vs. Junction
Iq (mA)
2
Vcc = 12V Vo = 3.3V Tj = 25C
1.8
1.6 Vcc = 12V DC = 0%
Figure 2. Line Regulation
Vo (V) 3.312 3.308 3.304 3.3 3.296 3.292 3.288 3.284 3.28 3.276 0 10 20 Vcc (V) 30 40 Tj = 125C Vcc = 12V Vo = 3.3V Tj = 25C
Figure 5. Shutdown Current vs.Junction Temperature
Ishd (A) 70
60
Vcc = 12V
50
40
30 -50 0 50 Tj (C) 100 150
Figure 3. Output Voltage vs. Junction Temperature
Vo (V) 1.25 1.24 1.23 1.22 Vcc = 12V 1.21 1.2 -50 0 50 Tj (C) 100 150 Vcc=12V
Figure 6. Switching Frequency vs.Junction Temperature
Iq (mA)
2
1.8
1.6 Vcc = 12V DC = 0%
1.4
1.2 -50 0 50 Tj (C) 100 150
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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
VCC
8
1
OUT
L1 33H D1 STPS2L25U
VOUT=3.3V
C1 10F 25V CERAMIC
COMP C4 22nF C3 220pF R3 4.7K
L5972D
4 6 2 3 7 5 FB GND
R1 5.6K
C2 100F 10V
R2 3.3K
D03IN1438
Table 1. Component List
Reference C1 C2 C3 C4 R1 R2 R3 D1 L1 STPS2L25U DO3316P-333 POSCAP 10TPB100M C1206C221J5GAC C1206C223K5RAC Part Number Description 10F, 25V 100F, 10V 220pF, 5%, 50V 22nF, 10%, 50V 5.6K, 1%, 0.1W 0603 3.3K, 1%, 0.1W 0603 4.7K, 1%, 0.1W 0603 2A, 25V 33H, 2.1A Manufacturer TOKIN Sanyo KEMET KEMET Neohm Neohm Neohm ST COILCRAFT
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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.
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Figure 11. Junction Temperature vs. Output Current
TJ(C) 100.0 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 0.2 0.4 0.6 0.8 1 1.2 Io(A) 1.4 1.6 1.8 2
Figure 13. Efficiency vs. Output Current
95 93 91
Vo=3.3V
Vin=5V Tamb.=25 C
Vo=2.5V
Vo=3.3V
Efficiency (%)
89 87 85 83 81 79 77 75 73 71 69 67 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7
Vo=2.5V
Vo=1.8V
Vo=1.8V
Vcc=5V
Io (A)
Figure 12. Junction Temperature vs. Output Current
TJ(C) 100.0 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 0.2 0.4 0.6 0.8 1 1.2 Io(A) 1.4 1.6 1.8 2 Vo=2.5V Vin=12V Tamb= 25C Vo=5V Vo=3.3V
Figure 14. Efficiency vs. Output Current
96 94 92 90 88 Efficiency (%) 86 84 82 80 78 76 74 72 70 0.1 0.3 0.5 0.7 0.9 Io (A) 1.1 1.3 1.5 1.7 Vin=12V Vo=2.5V Vo=3.3V Vo=5V
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APPLICATION IDEAS Figure 15. Positive Buck-Boost regulator
L1 33uH
VIN=5V
Vcc
OUT
D2 STPS2L25U
VOUT=12V/0.45A
8
COMP C1 10uF 10V Ceramic
1 L5972D
FB D1 STPS2L25U 24k
4 2
C2 220pF C3 22nF R3 4.7k
6
GND
7
5 3
M1 STN4NE03L
2.7k
C4 100uF 16V
Figure 16. Buck-Boost regulator
OUT
VIN=5V
Vcc
L1 33uH
8
COMP C1 10uF 10V Ceramic
1 L5972D
FB D1 STPS2L25U 2.7k
C2 10uF C3 25V Ceramic 220pF
4 2
C4 22nF R3 4.7k
VOUT=-12V/0.45A
6
GND
7
5 3
24k
C5 100uF 16V
Figure 17. Dual output voltage with auxiliary winding
n=N1/N2=2 D2 N2 STPS2L25U VIN=12V Vcc OUT VOUT1=5V 50mA
8
COMP C1 10uF 25V
1 L5972D
FB
N1 D1 STPS2L25U
VOUT=3.3V
4 2
C2 220pF C3 22nF R3 4.7k
6
GND
7
5 3
C4 100uF 10V
C5 47uF 10V
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DIM. MIN. A a1 a2 a3 b b1 C c1 D (1) E e e3 F (1) L M S 3.8 0.4 4.8 5.8 0.65 0.35 0.19 0.25 0.1
mm TYP. MAX. 1.75 0.25 1.65 0.85 0.48 0.25 0.5 0.026 0.014 0.007 0.010 0.004 MIN.
inch TYP. MAX. 0.069 0.010 0.065 0.033 0.019 0.010 0.020
OUTLINE AND MECHANICAL DATA
45 (typ.) 5.0 6.2 1.27 3.81 4.0 1.27 0.6 8 (max.) 0.15 0.016 0.189 0.228 0.050 0.150 0.157 0.050 0.024 0.197 0.244
SO8
(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. 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 2003 STMicroelectronics - All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan -Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom - United States. http://www.st.com
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