STMICROELECTRONICS L4973

L4973
3.5A step down switching regulator
Features
■
Up to 3.5A step down converter
■
Operating input voltage from 8V to 55V
■
3.3V and 5.1V (±1%) fixed output, and
adjustable outputs from:
– 0.5V to 50V (3.3 type)
– 5.1V to 50V (5.1 type)
DIP-18 (12+3+3)
Description
■
Frequency adjustable up to 300kHz
■
Voltage feed forward
■
Zero load current operation (min 1mA)
■
Internal current limiting (pulse by pulse and
HICCUP mode)
■
Precise 5.1V (1.5%) reference voltage
externally available
■
Input/output synchronization function
■
Inhibit for zero current consumption (100mA
typ. at VCC = 24V)
■
Protection against feedback disconnection
■
Thermal shutdown
■
Output over voltage protection
■
Soft start function
Figure 1.
The L4973 is a step down monolithic power
switching regulator delivering 3.5A at fixed
voltages of 3.3V or 5.1V and using a simple
external divider output adjustable voltage up to
50V. Realized in BCD mixed technology, the
device uses an internal power D-MOS transistor
(with a typical RDS(on) of 0.15Ω) to obtain very
high efficiency and very fast switching times.
Switching frequency up to 300KHz are achievable
(the maximum power dissipation of the packages
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 the today applications.
Features of this new generation of DC-DC
converter includes pulse by pulse current limit,
hiccup mode for output short circuit protection,
voltage feed forward regulation, soft start,
input/output synchronization, protection against
feedback loop disconnection, inhibit for zero
current consumption and thermal shutdown.
Packages available are in plastic dual in line, DIP18 (12+3+3) for standard assembly, and SO20
(12+4+4) for SMD assembly.
Internal schematic diagram
VCC (8V to 55V)
7
C2
CBOOT
12
8
ROSC
CIN
SO-20 (12+4+4)
9
1
4,5,6,10
13,14,15
L4973
16
3
11
17
2
VO(3.3V or 5.1V)
L1
RCOMP
COSC
CSS
D1
COUT
CCOMP
D97IN554A
May 2007
Rev 17
1/27
www.st.com
27
Contents
L4973
Contents
1
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3
2.1
Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5
Evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6
Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7
Typical charcteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8
Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
10
Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
11
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2/27
L4973
1
Block diagram
Block diagram
Figure 2.
Block diagram
INH
VCC
V5.1
10(11)
16(18)
VCC
7(8)
8(9)
CBOOT
CHARGE
ZERO CURRENT
INHIBIT
VREF
GOOD
5.1V
INTERNAL
REFERENCE
INTERNAL
SUPPLY
5.1V
3.3V
17(19)
SS
COMP
HICCUP CURRENT
LIMITING
SOFT
START
11(12)
CURRENT
LIMITING
THERMAL
SHUTDOWN
5.1V
3.3V
VFB
12(13)
SYNC
+
E/A
-
PWM
+
R
Q
S
Q
9(10)
BOOT
OSCILLATOR
18(20)
DRIVER
4,5,6,13,14,15
(4,5,6,7,14,15,16,17)
1(1)
OSC
2(2)
GND
OUT
3(3)
OUT
D94IN161B
Pin x = Powerdip
Pin (x) = S020
2
Pin settings
2.1
Pin connection
Figure 3.
Pin connection (top view)
OSC
1
18
SYNC
OUT
2
17
SS
OUT
3
16
V5.1
GND
4
15
GND
GND
5
14
GND
GND
6
13
GND
VCC
7
12
VFB
VCC
8
11
COMP
BOOT
9
10
INH
OSC
1
20
SYNC
OUT
2
19
SS
OUT
3
18
V5.1
GND
4
17
GND
GND
5
16
GND
GND
6
15
GND
GND
7
14
GND
VCC
8
13
VFB
VCC
9
12
COMP
10
11
INH
BOOT
D94IN162A
D94IN163A
DIP -18 (12+3+3)
SO20 (12+4+4)
3/27
Pin settings
2.2
L4973
Pin description
Table 1. Pin description
N° Pin
Name
SO-20
11
12
COMP
10
11
INH
9
10
BOOT
A capacitor connected between this pin and the output
allows to drive the internal D-MOS.
18
20
SYNC
Input/Output synchronization.
7,8
8,9
VCC
Unregulated DC input voltage
2,3
2,3
OUT
Stepdown regulator output.
4/27
1
E/A output to be used for frequency compensation
A logic signal (active high) disables the device (sleep
mode operation). If not used it must be connected to
GND; if floating the device is disabled.
12
13
VFB
Stepdown feedback input. Connecting the output
directly to this pin results in an output voltage of 3.3V for
the L4973V3.3 and 5.1V for L4973V5.1. An external
resistive divider is required for higher output voltages.
For output voltage resistive divider is required for higher
output voltages. For output voltage less than 3.3V, see
Note: 1 and Figure 33.
16
18
V5.1
Reference voltage externally available.
4,5,6
13,14,15
4,5,6,7
14,15,16,17
GND
Signal ground
OSC
An external resistor connected between the unregulated
input voltage and Pin 1 and a capacitor connected from
Pin 1 to ground fixes the switching frequency. (Line feed
forward is automatically obtained)
1
Note:
Description
DIP-18
1
The maximum power dissipation of the package must be observed.
L4973
Electrical data
3
Electrical data
3.1
Maximum ratings
Table 2. Absolute maximum ratings
Symbol
Parameter
DIP-18
S0-20
V7,V8
V9,V8
V2,V3
V2,V3
I2,I3
I2,I3
V9-V8
V10-V8
V9
V10
V11
Value
Unit
Input voltage
58
V
Output DC voltage
Output peak voltage at t = 0.1µs f = 200KHz
-1
-5
V
V
Maximum output current
int. limit.
14
V
Bootstrap voltage
70
V
V12
Analogs input voltage (VCC = 24V)
12
V
V17
V19
Analogs input voltage (VCC = 24V)
13
V
V12
V13
(VCC = 20V)
6
-0.3
V
V
V18
V20
(VCC = 20V)
5.5
0.3
V
V
V10
V11
Inhibit
VCC
-0.3
V
V
5
1.3
2
W
W
W
4
W
-40 to 150
°C
Ptot
DIP 12+3+3
Power dissipation a Tpins ≤ 90°C
(TA = 70°C no copper area)
(TA = 70°C 4cm copper area on PCB)
SO-20
Power dissipation a Tpins = 90°C
TJ,TSTG
3.2
Junction and storage temperature
Thermal data
Table 3. Thermal data
Symbol
Parameter
RthJP
Maximum thermal resistance junction-pin
RthJA
Maximum thermal resistance junction-ambient
DIP-18
SO-20
Unit
12
15
°C/W
60 (1)
80 (1)
°C/W
1. Package mounted on board
5/27
Electrical characteristics
4
L4973
Electrical characteristics
Table 4. Electrical characteristics
(Refer to the test circuit,VCC = 24V; TJ = 25°C, COSC = 2.7nF; ROSC = 20KΩ;
unless otherwise specified)
Symbol
Parameter
Test condition
Min
Typ
Max
Unit
55
V
Dynamic characteristics
Input Voltage Range (1)
Output Voltage
L4973V5.1
Output Voltage
L4973V3.3
η
VO = VREF to 40V; IO = 3.5A
5.05
5.1
5.15
V
IO = 0.5A to 3.5A VCC = 8V
to 55V
5.00
5.1
5.20
V
4.95
5.1
5.25
V
IO = 1A
3.326
3.36
3.393
V
IO = 0.5A to 3.5A VCC = 8V
to 40V
3.292
3.36
3.427
V
3.26
3.36
3.46
V
0.15
0.22
Ω
0.35
Ω
VCC = 10.5V IO = 3.5A
Maximum Limiting
Current
VCC = 8V to 55V
(2)
(2)
(2)
(2)
3.8
4.5
5.5
A
4
4.5
5.5
A
VO = 5.1V; IO = 3.5A
90
%
VO = 3.3V; IO = 3.5A
85
%
(2)
Switching Frequency
∆fsw
8
IO = 1A
RDS(on )
Efficiency
(2)
Supply Voltage Ripple
Rejection
Vi = VCC+2VRMS VO = Vref;
IO = 1A; fripple = 100Hz
Switching Frequency
Stability vs., Supply
Voltage
VCC = 8V to 55V
90
100
110
60
KHz
dB
2
5
%
5.025
5.1
5.175
V
4.950
5.1
5.250
V
Reference section
Reference Voltage
(2)
Line Regulation
Iref = 0mA;
VCC = 8 to 55V
5
10
mV
Load Regulation
Vref = 0 to 5mA;
VCC = 0 to 20mA
2
6
10
25
mV
mV
65
100
mA
Short Circuit Current
6/27
Iref = 0 to 20mA;
VCC = 8 to 55V
30
L4973
Electrical characteristics
Table 4. Electrical characteristics (continued)
(Refer to the test circuit,VCC = 24V; TJ = 25°C, COSC = 2.7nF; ROSC = 20KΩ;
unless otherwise specified)
Symbol
Parameter
Test condition
Min
Typ
Max
Unit
Soft Start Charge
Current
30
45
60
µA
Soft Start Discharge
Current
15
22
30
µA
Soft start
Inhibit
High Level Voltage
(2)
Low Level Voltage
(2)
3.0
V
0.8
V
Isource High Level
VINH = 3V
(2)
10
16
50
µA
Isource Low Level
VINH = 0.8V
(2)
10
15
50
µA
4
6
mA
2.7
4
mA
100
200
µA
150
300
µA
DC characteristics
Total Operating
Quiescent Current
Duty Cycle = 50%
Quiescent Current
Duty Cycle = 0
VCC = 24V; VINH = 5V
Total stand-by quiescent
current
VCC = 55V; VINH = 5V
Error amplifier
High Level Output
Voltage
11.0
V
Low Level Output
Voltage
0.65
V
1
2
3
µA
Source Output Current
200
300
600
µA
Sink Output Current
200
300
µA
Source Bias Current
Supply Voltage Ripple
Rejection
VCOMP = VFB
CREF = 4.7µF 1-5mA load
current
60
80
dB
DC Open Loop Gain
RL = ∞
50
60
dB
Transconductance
Icomp = -0.1 to 0.1mA;
Vcomp = 6V
2.5
mS
Oscillator section
Ramp valley
0.78
0.85
0.92
V
7/27
Electrical characteristics
L4973
Table 4. Electrical characteristics (continued)
(Refer to the test circuit,VCC = 24V; TJ = 25°C, COSC = 2.7nF; ROSC = 20KΩ;
unless otherwise specified)
Symbol
Parameter
Ramp peak
Test condition
VCC = 8V
VCC = 55V
Maximum Duty Cycle
Maximum Frequency
Min
Typ
Max
Unit
1.9
9
2.1
9.6
2.3
10.2
V
V
95
97
Duty Cycle = 0%;
ROSC =13KΩ; COSC = 820pF;
%
300
KHz
Sync function
High Input Voltage
VCC = 8V to 55V
Low Input Voltage
VCC = 8V to 55V
Slave Sink Current
Master Output
Amplitude
Isource = 3mA
Output Pulse Width
no load, Vsync = 4.5V
1. Pulse testing with a low duty cycle
2. Specifications referred to TJ from -40°C to 125°C.
8/27
3.5
V
0.9
V
0.45
mA
0.15
0.25
4
4.5
V
0.20
0.35
µs
L4973
5
Evaluation board
Evaluation board
Figure 4.
Evaluation board circuit
VCC
(DIP18)
R2
7,8
12
1
C1
C2
C7
16
9
L4973
17
10
11
C8
4,5,6
2,3
13,14,15
L1
VO
R3
C3
C4
C5
D1
R1
3x
C0
C12
C6
R4
D97IN515C
C1=1000µF/63V
C2=220nF/63V
C3=470nF
C4=1µF/50V
C5=220pF
C6=22nF
C7=2.7nF
C8=220nF/63V
C0=100µF/40V(C9,C10,C11)
C12=Optional (220nF)
L1=150µH KOOLµ 77310 - 40 Turns - 0.9mm
R1=9.1K
R2=20K
D1=STPS5L60
L4973 V3.3
VO(V)
R3(KΩ)
3.3
0
5.1
2.7
12
12
15
L4973 V5.1
R4(KΩ)
VO(V)
R3(KΩ)
5.1
0
R4(KΩ)
4.7
12
6.2
4.7
4.7
15
9.1
4.7
16
4.7
18
12
4.7
18
20
4.7
24
18
4.7
24
30
4.7
Table 5. Typical performance (using evaluation board) fSW = 100kHz
Output voltage
Output
ripple
Efficiency
Line regulator
Io = 3.5A VCC = 8 to 50V
Load regulator
VCC =35V IO = 1 to 3.5A
3.3V
20mV
81.5 (%)
3mV
6mV
5.1V
20mV
86.7 (%)
3mV
6mV
12V
30mV
93.5 (%)
3mV (VCC =15 to 50V)
4mV
9/27
Evaluation board
10/27
L4973
Figure 5.
Evaluation board (components side)
Figure 6.
Evaluation board (solder side)
L4973
6
Application circuit
Application circuit
Figure 7.
Application circuit (see Figure 4 part list)
VCC
R2
INH
SYNC
10
18
7,8
9
C8
1
L4973V5.1
17
C1
C2
C7
C3
16
C4
4,5,6
13,14,15
11
C5
L1
12
Vo
2,3
3x
C0
D1
R1
C12
C6
D97IN665A
Figure 8.
Application circuit (see Figure 4 part list)
VCC
R2
7,8
INH
SYNC
10
18
9
C8
1
L4973V3.3
17
C1
C2
C7
C3
16
C4
C5
4,5,6
13,14,15
11
R1
L1
12
Vo
2,3
D1
3x
C0
C12
C6
D97IN664A
11/27
Typical characteristics
7
L4973
Typical characteristics
Figure 9.
Quiescent drain current vs.
input voltage (0% duty cycle)
Ibias
(mA)
D97IN633A
Figure 10. Quiescent drain current vs.
junction temperature
Ibias
(mA)
D97IN634
200KHz-R2=22K
C7=1.2nF
5.0
Tamb=25˚C
0% DC
200KHz-R2=22K
C7=1.2nF
4.0
4.5
100KHz-R2=20K
C7=2.7nF
4.0
100KHz-R2=20K
C7=2.7nF
3.5
3.5
0% DC
VCC = 35V
0Hz
3.0
3.0
0Hz
2.5
2.0
0
10
20
30
40
50 VCC(V)
Figure 11. Stand by drain current vs.
input voltage
Ibias
(µA)
D97IN635A
2.5
-50
0
50
100
Tj(˚C)
Figure 12. Reference voltage vs. junction
temperature (pin 16)
VREF
(V)
D97IN637
Pin 16
Vinh = 5V
5.15
150
Vcc=35V
25˚C
5.1
100
125˚C
5.05
50
0
12/27
10
20
30
40
50 VCC(V)
5.0
-40 -20
0
20
40
60
80 100 Tj(˚C)
L4973
Typical characteristics
Figure 13. Reference voltage vs.
input voltage (pin 16)
VREF
(V)
Figure 14. Reference voltage vs.
reference input current
D97IN636A
Tj=25˚C
Pin 16
VREF
(V)
5.15
5.2
5.1
5.1
D97IN638
Vcc=40V
Vcc=10V
5.0
5.05
Tj=25˚C
4.9
5.0
0
10
20
30
40
Figure 15. Inhibit current vs. inhibit
voltage (pin 10)
Iinh
(µA)
D97IN651
Vcc=35V
Pin 10
0
50 VCC(V)
10
20
30
40
50 IREF(mA)
Figure 16. Line regulation (see Figure 7)
VO
(V)
D97IN639A
Tj=0˚C
5.12
100
Tj=125˚C
˚C
5
=2
Tj
Tj=25˚C
5.1
50
Tj=125˚C
5.08
0
IO = 1A
5.06
-50
0
5
10
15
0
Vinh(V)
10
20
30
40
50
VCC(V)
Figure 17. Load regulation (see Figure 7) Figure 18. Line regulation (see Figure 8)
VO
(V)
D97IN640
VO
(V)
D97IN660A
3.35
VCC = 35V
5.15
Tj=125˚C
3.34
Tj=125˚C
Tj=25˚C
3.33
5.1
Tj=25˚C
3.32
5.05
IO = 1A
3.31
3.3
5.0
0
1
2
3
IO(A)
0
10
20
30
40
50
VCC(V)
13/27
Typical characteristics
L4973
Figure 19. Load regulation (see Figure 4) Figure 20. Switching frequency vs.
R2 and C7 (Figure 4)
VO
(V)
D97IN661
fsw
(KHz)
D97IN630
500
VCC = 35V
3.35
Tamb=25˚C
0.8
2nF
200
3.34
1.2
Tj=125˚C
nF
100
2.2
3.33
50
nF
3.3n
F
Tj=25˚C
3.32
4.7n
F
20
5.6n
F
3.31
10
5
3.3
0
1
2
3
Figure 21. Switching frequency vs.
input voltage
fsw
(KHz)
0
IO(A)
D97IN631
20
40
60
80
R2(KΩ)
Figure 22. Switching frequency vs.
junction temperature
(see Figure 4)
fsw
(KHz)
D97IN632
Tamb=25˚C
105
105
100
100
95
95
90
90
0
14/27
10
20
30
40
50 VCC(V)
-50
0
50
100
Tj(˚C)
L4973
Typical characteristics
Figure 23. Dropout voltage between pin
7,8 and 2,3
∆V
(V)
D97IN643
η
(%)
D97IN641
98
Tj=125˚C
0.6
Figure 24. Efficiency vs. output voltage
(see Figure 6)
100KHz
C
5˚
96
=2
Tj
94
200KHz
0.4
92
Tj=0˚C
90
0.2
IO = 3A
VCC = 50V
88
86
0
0
1
2
3
Figure 25. Dropout voltage between pin
7,8 and 2,3
∆V
(V)
D97IN643
10
20
30
40 VO(V)
Figure 26. Efficiency vs. output voltage
(see Figure 4)
η
(%)
D97IN641
98
Tj=125˚C
0.6
0
IO(A)
100KHz
C
5˚
=2
Tj
96
94
200KHz
0.4
92
Tj=0˚C
90
0.2
IO = 3A
VCC = 50V
88
86
0
0
1
2
3
IO(A)
0
10
20
30
40 VO(V)
15/27
Typical characteristics
L4973
Figure 27. Efficiency vs. output voltage
(Diode STPS745D)
η
(%)
D97IN642
Figure 28. Efficiency vs. output current (
see Figure 7)
η
(%)
D97IN645
98
VO = 5.1V
fsw = 100KHz
100KHz
95
96
Vcc=12V
94
200KHz
90
92
Vcc=24V
90
Vcc=48V
85
IO = 3A
VCC = 35V
88
86
80
0
5
10
15
20
25
30
Figure 29. Efficiency vs. output current
(see Figure 7)
η
(%)
0
VO(V)
D97IN646
1
2
3
IO(A)
Figure 30. Efficiency vs. output current
(see Figure 8)
η
(%)
D97IN644
VO = 3.3V
fsw = 100KHz
Vcc=12V
90
90
Vcc=12V
Vcc=24V
85
85
Vcc=24V
Vcc=48V
80
80
VO = 5.1V
fsw = 200KHz
75
75
0
16/27
Vcc=48V
1
2
3
IO(A)
0
1
2
3
IO(A)
L4973
Typical characteristics
Figure 31. Efficiency vs. output current
(see Figure 8)
η
(%)
D97IN662
Pdiss
(W)
D97IN647A
VO = 5.1V
fsw = 100KHz
VO = 3.3V
fsw = 200KHz
90
Figure 32. Power dissipation vs. input
voltage (device only)
(see Figure 7)
1.5
Vcc=12V
IO=3.5A
85
Vcc=24V
IO=3A
1.0
80
IO=2.5A
Vcc=48V
0.5
75
IO=2A
0
70
0
0.5
1
1.5
2
2.5
3
Figure 33. Power dissipation vs. output
voltage (device only)
Pdiss
(W)
D97IN648
3.0
VCC = 35V
fsw = 100KHz
0
3.5 IO(A)
10
20
30
40
50
Vcc(V)
Figure 34. Pulse by pulse limiting
current vs.
junction temperature
Ilim
(A)
D97IN652
5.2
IO=3.5A
2.5
5
2.0
IO=3A
1.5
IO=2.5A
4.8
Vcc=35
4.6
1.0
IO=2A
0.5
IO=1A
4.4
0
0
5
10
15
20
25
30
VO(V)
4.2
-40 -20 0
20 40 60 80 100 120
Tj(˚C)
17/27
Typical characteristics
L4973
Figure 35. Load transient
IO
(A)
Figure 36. Line transient
VCC
(V)
D97IN649
3
30
2
20
1
D97IN650
10
T
VO
(mV)
2
VO
(mV)
1
200µs/DIV
IO = 1A
fsw = 100KHz
100
1
T
0
VCC = 35V
fsw = 100KHz
2
0
-100
-100
Figure 37. Source current rise and fall
time, pin 2, 3 (see Figure 4)
100
1ms/DIV
Figure 38. Soft start capacitor selection
vs. inductor and VCC max (ref.
AN938)
Lomax
(µH)
D97IN653
Css=1µF
Css=820nF
300
fsw = 100KHz
250
Css=680nF
200
Css=470nF
150
100
Css=220nF
Css=100nF
50
0
25
18/27
30
35
40
45
50
Vi(V)
L4973
Typical characteristics
Figure 39. Soft start capacitor selection Figure 40. Open loop frequency and
vs. inductor and VCC max (ref.
phase of error amplifier
AN938)
Lomax
(µH)
Cs
s=6
8nF
Cs
s=
56
nF
D97IN654
fsw = 200KHz
GAIN
(dB)
D97IN663
Phase
50
GAIN
0
0
-50
45
Cs
s=
47
nF
150
100
nF
3
=3
s
Cs
90
-100
F
50
n
22
Phase
s=
Cs
135
-150
-200
0
15
20
25
30
35
40
45
50 Vi(V)
10
102 103 104 105 106 107 108 f(Hz)
19/27
Application ideas
8
L4973
Application ideas
Figure 41. 3.5A at VO < 3.3V (see part list Figure 4)
VCC
R2
7,8
INH
SYNC
10
18
9
C7
11
R1
C5
D1
C4
C6
1.5
2K
2K
2
4.7K
3.6K
2.5
7.5K
3.6K
3
5.1K
1K
VO=3.36-1.74•
R3
R5
Vo
12
R5
C3
4.7K
2,3
4,5,6
13,14,15
16
R3
3.6K
L1
L4973V3.3
17
C2
R5
1
C8
1
C1
VP
R3
3x
C0
D97IN666A
Figure 42. 12V to 3.3V high performance buck converter (fsw = 200kHz)
VCC
12V±5%
R2
22k
7,8
INH
SYNC
10
18
16
C2
220nF
C3
33nF
L4973V3.3
17
C7
1.2nF
C1
560uF-25V
HFQ
Panasonic
C4
1uF
C5
220pF
4,5,6
13,14,15
11
R1
9k1
C6
22nF
η
(%)
C8
220nF
9
1
92
L1
2,3
90
12
Vo=3.33V
Io=3.5A
D1
C9
470uF-25V
HFQ
Panasonic
88
86
84
82
L1
D1
20/27
KoolMm 77120- 24 Turns- 0.9mm
STPS1025
D97IN668A
80
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Io(A)
L4973
Application ideas
Figure 43. Synchronization example
VCC2
VCC1
7,8
7,8
1
VCC
L4973
18
18
4,5,6
13,14,15
L4973
7,8
1
1
18
7,8
L4973
L4973
4,5,6
13,14,15
4,5,6
13,14,15
18
4,5,6
13,14,15
1
D97IN669
Figure 44. Multi output not isolated (pin out referred to DIP12+3+3)
VCC
INH
SYNC
10
18
7,8
Vo2
D2
C8
R2
9
1
C1
C2
C7
C3
C4
C5
17
L4973
16
4,5,6
13,14,15
11
R1
n2
12
2,3
L1
Vo1
n1
D1
C9
C10
C11
C6
VO2 = VO1
n1 + n2
n1
D97IN667A
PO2 < 20% PO1
21/27
Package mechanical data
9
L4973
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
22/27
L4973
Package mechanical data
Table 6. DIP-18 mechanical data
mm.
inch
Dim.
Min
a1
0.51
B
0.85
b
b1
Typ
Max
Min
Typ
Max
0.020
1.40
0.033
0.50
0.38
0.020
0.50
D
0.055
0.015
0.020
24.80
0.976
E
8.80
0.346
e
2.54
0.100
e3
20.32
0.800
F
7.10
0.280
I
5.10
0.201
L
3.30
Z
0.130
2.54
0.100
Figure 45. Package dimensions
23/27
Package mechanical data
L4973
Table 7. SO-20 mechanical data
mm.
inch
Dim.
Min
Typ
Min
Typ
Max
A
2.35
2.65
0.093
0.104
A1
0.10
0.30
0.004
0.012
B
0.33
0.51
0.013
0.200
C
0.23
0.32
0.009
0.013
D (1)
12.60
13.00
0.496
0.512
E
7.40
7.60
0.291
0.299
e
1.27
0.050
H
10.0
10.65
0.394
0.419
h
0.25
0.75
0.010
0.030
L
0.40
1.27
0.016
0.050
k
ddd
Figure 46. Package dimensions
24/27
Max
0° (min.), 8° (max.)
0.10
0.004
L4973
10
Order code
Order code
Table 8. Order code
Part number
Package
Packaging
L4973D3.3, E-L4973D3.3
SO-20
Tube
L4973D3.3-013TR, E-L4973D3.3-TR
SO-20
Tape and reel
L4973D5.1
SO-20
Tube
L4973D5.1-013TR
SO-20
Tape and reel
L4973V3.3, E-L4973V3.3
DIP-18
Tube
L4973V5.1, E-L4973V5.1
DIP-18
Tube
25/27
Revision history
11
L4973
Revision history
Table 9. Revision history
26/27
Date
Revision
Changes
12-Sep-2001
13
First Issue
07-May-2005
14
Updated the Layout look & feel.
Changed name of the D1 on the fig. 5.
14-Dec-2005
15
Added the ECOPACK part numbers in the Table 1. Order Codes.
06-Dec-2006
16
The document has been reformatted, and order codes updated
07-May-2007
17
New data on Table 4
L4973
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27/27