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(R)
L4976
1A STEP DOWN SWITCHING REGULATOR
UP TO 1A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM 8V TO 55V PRECISE 5.1V REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM 3.3V TO 50V SWITCHING FREQUENCY ADJUSTABLE UP TO 500KHz VOLTAGE FEEDFORWARD ZERO LOAD CURRENT OPERATION INTERNAL CURRENT LIMITING (PULSE-BYPULSE AND HICCUP MODE) PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN DESCRIPTION The L4976 is a step down monolithic power switching regulator delivering 1A at a voltage between 3.3V and 50V (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 0.25) to obtain very high efficency and high switching speed. A switching frequency up to 250KHz is achievable (the maximum power dissipation of the packTYPICAL APPLICATION CIRCUIT
Minidip
SO16W
ORDERING NUMBERS: L4976 (Minidip) L4976D (SO16)
ages must be observed). A wide input voltage range between 8V to 55V and output voltages regulated from 3.3V to 40V 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, protection against feedback loop disconnection and thermal shutdown. The device is available in plastic dual in line, MINIDIP 8 for standard assembly, and SO16W for SMD assembly.
Vi=8V to 55V 5 R1 20K 3 C1 220F 63V C7 220nF C2 2.7nF 2 7 8
L4976
4 1 6 L1 260H (77120) D1 GI SB360 C8 330F VO=3.3V/1A
R2 9.1K C4 22nF
C6 100nF
May 2000
1/11
L4976
BLOCK DIAGRAM
VCC 5 THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE VREF 2 VREF 5.1V COMP FB 7 8 E/A 3.3V PWM R S Q DRIVE OSCILLATOR CBOOT CHARGE AT LIGHT LOADS INTERNAL REFERENCE 6
BOOT
3.3V
3 OSC
1 GND
4 OUT
PIN CONNECTIONS
N.C. GND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 N.C. N.C. FB COMP BOOT VCC N.C. N.C.
GND VREF OSC OUT
1 2 3 4
8 7 6 5
FB COMP BOOT VCC
VREF OSC OUT OUT N.C. N.C.
Minidip
SO16W
PIN FUNCTIONS
DIP 1 2 3 SO (*) 2 3 4 Name GND VREF OSC Function Ground 5.1V Reference voltage with 20mA current capability. 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) Stepdown regulator output Unregulated DC input voltage A capacitor connected between this pin and OUT allows to drive the internal VDMOS E/A output to be used for frequency compensation 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.
4 5 6 7 8
5, 6 11 12 13 14
OUT VCC BOOT COMP FB
(*) Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die.
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L4976
THERMAL DATA
Symbol R th(j-amb) Parameter Thermal Resistance Junction to ambient Max. Minidip 90 (*) SO16 110 (*) Unit C/W
(*) Package mounted on board.
OPERATING TEMPERATURE RATING
Symbol TJ Parameter Junction Temperature Range Value -40 to 150 Unit C
ABSOLUTE MAXIMUM RATINGS
Symbol Minidip V5 V4 I4 V6-V5 V6 V7 V8 Ptot Tj,Tstg S016 V11 V5,V6 I5,I6 V12-V11 V12 V13 V14 Bootstrap voltage Analogs input voltage (VCC = 24V) (VCC = 20V) Power dissipation a Tamb 60C Junction and storage temperature Minidip SO16 Input voltage Output DC voltage Output peak voltage at t = 0.1s f=200KHz Maximum output current Parameter Value 58 -1 -5 int. limit. 14 70 12 6 -0.3 1 0.8 -40 to 150 V V V V V W W C Unit V V V
ELECTRICAL CHARACTERISTICS (Tj = 25C, Cosc = 2.7nF, Rosc = 20k, VCC = 24V, unless otherwise specified.) * Specification Refered to Tj from 0 to 125C
Symbol VI Vo Parameter Operating input voltage range Output voltage Test Condition Vo = 3.3 to 50V; Io = 1A Io = 0.5A Io = 0.2 to 1A Vcc = 8 to 55V Vcc = 10V; Io = 1A Vcc = 8 to 55V Vo = 3.3V; Io = 1A Vi = Vcc+2VRMS; Vo = Vref; Io = 1.A; f ripple = 100Hz Vcc = 8 to 55V Tj = 0 to 125C * Min. 8 3.33 3.292 3.22 Typ. Max. 55 3.39 3.427 3.5 0.55 0.88 2.5 110 Unit V V V V V V A % KHz dB % %
DYNAMIC CHARACTERISTIC
3.36 3.36 3.36 0.44 2 85 100
* * * *
Vd Il fs SVRR
Dropout voltage Maximum limiting current Efficiency Switching frequency Supply voltage ripple rejection Voltage stability of switching frequency Temp. stability of switching frequency
1.5 90 60
3 4
6
3/11
L4976
ELECTRICAL CHARACTERISTICS (continued)
Symbol Parameter Reference Section Reference Voltage Test Condition Min. 5.0 4.950 Typ. 5.1 5.1 5 2 6 65 Max. 5.2 5.250 10 10 25 100 Unit V V mV mV mV mA
Line Regulation Load Regulation Short Circuit Current
Iref = 0 to 10mA; VCC = 8 to 55V Iref = 0mA; VCC = 8 to 55V Vref = 0 to 5mA; VCC = 0 to 20mA
*
30
DC Characteristics
Iqop Iq VFB RL Total operating quiescent current Quiescent current Voltage Feedback Input Line regulation Ref. voltage stability vs temperature High level output voltage Low level output voltage Source output current Sink output current Source bias current Supply voltage ripple rejection DC open loop gain Transconductance 4 Duty Cycle = 0; VFB = 3.8V 3.33 Vcc = 8 to 55V * VFB = 2.5V VFB = 3.8V Vcomp = 6V; V FB = 2.5V Vcomp = 6V; V FB = 3.8V Vcomp = Vfb; Vcc = 8 to 55V RL = Icomp = -0.1 to 0.1mA Vcomp = 6V 10.3 0.65 180 200 60 50 220 300 2 80 57 2.5 2.5 3.36 5 0.4 6 3.5 3.39 10 mA mA V mV mV/C V V A A A dB dB ms
Error Amplifier
VoH VoL Io source Io sink Ib SVRR E/A gm
3
Oscillator Section
Ramp Valley Ramp peak Maximum duty cycle Maximum Frequency Vcc = 8V Vcc = 55V Duty Cycle = 0% Rosc = 13k, Cosc = 820pF 0.78 2 9 95 0.85 2.15 9.6 97 0.92 2.3 10.2 500 V V V % kHz
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L4976
Figure 1. Quiescent drain current vs. input voltage.
Iq (mA)
200KHz R 1=22K C 2=1.2nF 100KHz R 1=20K C 2=2.7nF
D97IN724
Figure 2. Quiescent current vs. junction temperature
Iq (mA) 5
D97IN731
5
200KHz R1=22K C2=1.2nF 100KHz R1 =20K C2 =2.7nF 0Hz
4
4
3
0Hz
3
VCC=35V 0% DC
2
Tamb=25C 0% DC
2
1 0 5 10 15 20 25 30 35 40 45 50 Vcc(V)
1 -50 -30 -10 10 30 50 70 90 110 Tj(C)
Figure 3. Line Regulation
VO (V) 3.377
Tj=125C
D97IN733
Figure 4. Load regulation
VO (V) 3.378 3.376 3.374
Tj=25C
Tj=25C
D97IN734
VCC=35V
3.376 3.375 3.374 3.373 3.372 3.371 3.370 0 5 10 15 20 25 30 35 40 45 50 VCC(V)
3.372 3.370 3.368 3.366 3.364 3.362 3.360 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 I O(A)
Tj=125C
Figure 5. Switching frquency vs. R1 and C2
fsw (KHz) 500
0.8
Figure 6. Switching Frequency vs. input voltage.
fsw (KHz) 107.5 105.0
D97IN735
D97IN784
Tamb=25C
200 100 50 20
2nF 1.2 nF
102.5
nF
F
Tj=25C
2.2
100.0 97.5
4.7n F
3.3n
5.6n
F
95.0 92.5
10 5 0 20 40 60 80 R1(K)
90.0 0 5 10 15 20 25 30 35 40 45 50 VCC(V)
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L4976
Figure 7. Switching frequency vs. junction temperature.
fsw (KHz)
D97IN785
Figure 8. Dropout voltage between pin 5 and 4.
V (V) 0.5
Tj=125C
D97IN736
105
0.4
Tj =2 C 5
100
0.3 0.2
Tj=-25C
95
0.1 0.0
90 -50 0 50 100 Tj(C)
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)
Figure 9. Efficiency vs output voltage.
(%) 96 94 92
100KHz
D97IN737
Figure 10. Efficiencyvs. output current.
(%) 90 85
VCC=24V VCC=12V
D97IN738
VCC=8V
200KHz
80
90 88 86 84 82 0 5 10 15 20 25 VO(V)
VCC=35V IO=1.5A
75 70 65
VCC =48V fsw=100KHz VO=5.1V
60 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)
Figure 11. Efficiencyvs. output current.
(%) 90 85 80 75 70 65 60 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)
VCC=48V VCC =12V VCC=24V VCC=8V
D97IN739
Figure 12. Efficiencyvs. output current.
(%) 90 85 80
V CC=48V V CC=12V VCC=24V
D97IN740
VCC=8V
75
fsw=100KHz VO=3.36V
70 65 60
fsw=200KHz V O=5.1V
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)
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L4976
Figure 13. Efficiencyvs. output current.
(%) 90 85 80 75 70 65 60 55 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A) 70 0 10 20 30 40 50 VCC(V)
VCC=48V fsw=200KHz VO=3.36V VCC=8V VCC=12V VCC=24V
V0=
D97IN741
Figure 14. Efficiencyvs. Vcc.
(%)
V0=5 .1V-f
SW=10
D97IN742
0KHz
85
V0 =
5.1
V-f
SW
=2
00
KH
z
100
80
3.36
-fS
V
V-f
0=
3.3
SW =
6V
KHz
W=
75
12 0
0K
IO=1.5A
Hz
Figure 15. Power dissipation vs. Vcc.
Pdiss (mW)
V O=5.1V fsw=100KHz
D97IN743
Figure 16. Efficiencyvs. Vo.
Pdiss (mW)
VCC=35V fsw=100KHz
D97IN744
800
800
IO=1.5A IO=1.5A IO=1A
600
600
IO=1A
400
IO=0.5A
400
IO=0.5A
200
200
0
0
10
20
30
40
50 VCC(V)
0
0
5
10
15
20
25
30 V0(V)
Figure 17. Pulse by pulse limiting current vs. junction temperature.
Ilim (A) 2.9 2.8 2.7 2.6 2.5 2.4 2.3 -50 -25 0 25 50 75 100 125 Tj(C)
fsw=100KHz VCC=35V
D97IN747
Figure 18. Load transient.
7/11
L4976
Figure 19. Line transient.
VCC (V) 30
D97IN786
Figure 20. Open loop frequency and phase of error amplifier
GAIN (dB) 50
D97IN787
Phase
20 10 1
I O = 1A f sw = 100KHz
GAIN
0
0 45 90
Phase
VO (mV) 100
-50 -100
2
0 -100
1ms/DIV
-150 -200 10
135
102 103 104 10 5 10 6 10 7 108 f(Hz)
8/11
L4976
DIM. MIN. A a1 B b b1 D E e e3 e4 F I L Z 3.18 7.95 0.51 1.15 0.356 0.204
mm TYP. 3.32 0.020 1.65 0.55 0.304 10.92 9.75 2.54 7.62 7.62 6.6 5.08 3.81 1.52 0.125 0.313 0.045 0.014 0.008 MAX. MIN.
inch TYP. 0.131 MAX.
OUTLINE AND MECHANICAL DATA
0.065 0.022 0.012 0.430 0.384 0.100 0.300 0.300 0.260 0.200 0.150 0.060
Minidip
9/11
L4976
DIM. MIN. A A1 B C D E e H h L K 10 0.25 0.4 2.35 0.1 0.33 0.23 10.1 7.4
mm TYP. MAX. 2.65 0.3 0.51 0.32 10.5 7.6 1.27 10.65 0.75 1.27 0.394 0.010 0.016 MIN. 0.093 0.004 0.013 0.009 0.398 0.291
inch TYP. MAX. 0.104 0.012 0.020 0.013 0.413 0.299 0.050 0.419 0.030 0.050
OUTLINE AND MECHANICAL DATA
0 (min.)8 (max.)
SO16 Wide
L
h x 45
A B e K H D A1 C
16
9
E 1 8
10/11
L4976
Information furnished is believed to be accurate and reliable. However, STMicroelectroni cs 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. Specification 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 (c) 2000 STMicroelectronics GROUP OF COMPANIES Australia - Brazil - China - Finland - France - Germany - Hong Kong - India - Italy - Japan - Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom - U.S.A. http://www.st.com
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