®
L4973V3.3 - L4973V5.1
L4973D3.3 - L4973D5.1
3.5A STEP DOWN SWITCHING REGULATOR
UPTO 3.5ASTEP DOWNCONVERTER
OPERATING INPUT VOLTAGE FROM 8V TO
55V
3.3V AND 5.1V (±1%) FIXED OUTPUT, AND
ADJUSTABLE OUTPUTS FROM:
0V TO 50V (3.3V type)
5.1V TO 50V (5.1 type)
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 VOLT-
AGE EXTERNALLY AVAILABLE
INPUT/OUTPUT SYNCHRONIZATION FUNC-
TION
INHIBIT FOR ZERO CURRENT CONSUMP-
TION (100µA Typ. at V
CC
= 24V)
PROTECTION AGAINST FEEDBACK DIS-
CONNECTION
THERMAL SHUTDOWN
OUTPUT OVERVOLTAGE PROTECTION
SOFT START FUNCTION
TYPICAL APPLICATION CIRCUIT (POWERDIP)
MULTIPOWER BCD TECHNOLOGY
POWERDIP (12+3+3)
SO20(12+4+4)
ORDERING NUMBERS:
L4973V3.3 (Powerdip)
L4973D3.3
(SO20)
L4973V5.1 (Powerdip)
L4973D5.1
(SO20)
DESCRIPTION
The L4973 is a step down monolithic power
switching regulator delivering 3.5A at fixed volt-
ages 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
V
CC
(8V to 55V)
R
OSC
C
IN
C2
7
8
10 12
C
BOOT
V
O
(3.3V or 5.1V)
L1
1
4,5,6,
13,14,15 16
L4973
17
9
3
11 2
R
COMP
C
OSC
C
SS
C
COMP
D1
C
OUT
D97IN554A
April 2000
1/16
L4973V3.3 - L4973V5.1 - L4973D3.3 - L4973D5.1
uses an internal power D-MOS transistor (with a
typical Rdson of 0.15ohm) to obtain very high effi-
ciency 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 con-
PIN CONNECTIONS (Top view
)
verter 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 consump-
tion and thermal shutdown.
Packages available are in plastic dual in line, DIP-
18 (12+3+3) for standard assembly, and SO20
(12+4+4) for SMD assembly.
OSC
OUT
OUT
GND
GND
GND
V
CC
V
CC
BOOT
1
2
3
4
5
6
7
8
9
D94IN162A
18
17
16
15
14
13
12
11
10
SYNC
SS
V5.1
GND
GND
GND
VFB
COMP
INH
OSC
OUT
OUT
GND
GND
GND
GND
V
CC
V
CC
BOOT
1
2
3
4
5
6
7
8
9
10
D94IN163A
20
19
18
17
16
15
14
13
12
11
SYNC
SS
V5.1
GND
GND
GND
GND
VFB
COMP
INH
POWERDIP (12+3+3)
SO20 (12+4+4)
BLOCK DIAGRAM
INH
10(11)
V5.1
16(18)
V
CC
7(8)
8(9)
CBOOT
CHARGE
ZERO CURRENT
INHIBIT
VREF
GOOD
INTERNAL
REFERENCE
INTERNAL
SUPPLY
5.1V
V
CC
5.1V
3.3V
SS
17(19)
SOFT
START
HICCUP CURRENT
LIMITING
COMP
11(12)
THERMAL
SHUTDOWN
5.1V
3.3V
+
E/A
-
CURRENT
LIMITING
R
S
Q
Q
9(10)
BOOT
VFB
-
PWM
12(13)
+
SYNC
18(20)
OSCILLATOR
DRIVER
1(1)
OSC
4,5,6,13,14,15
(4,5,6,7,14,15,16,17)
GND
2(2)
OUT
3(3)
OUT
D94IN161B
Pin x = Powerdip
Pin (x) = S020
2/16
L4973V3 - L4973V5 - L4973D3 - L4973D5
THERMAL DATA
Symbol
R
th(j-pin)
R
th(j-amb)
Parameter
Thermal Resistance Junction to pin
Thermal Resistance to Ambient
Max.
Max.
Powerdip
12
60 (*)
SO20
15
80 (*)
Unit
°C/W
°C/W
(*) Package mounted on board.
ABSOLUTE MAXIMUM RATINGS
Symbol
DIP-18
V
7
,V
8
V
2
,V
3
I
2
,I
3
V
9
-V
8
V
9
V
11
V
17
V
12
V
18
V
10
P
tot
S0-20
V
9
,V
8
V
2
,V
3
I
2
,I
3
V
10
-V
8
V
10
V
12
V19
V
13
V
20
V
11
Bootstrap voltage
Analogs input voltage (V
CC
= 24V)
Analogs input voltage (V
CC
= 24V)
(V
CC
= 20V)
(V
CC
= 20V)
Inhibit
Power dissipation a T
pins
≤
90°C
(T
amb
= 70°C no copper area)
(T
amb
= 70°C 4cm copper area on PCB)
Power dissipation a T
pins
= 90°C
T
J
,T
STG
Junction and storage temperature
DIP
12+3+3
SO20
Input voltage
Output DC voltage
Output peak voltage at t = 0.1µs f=200KHz
Maximum output current
Parameter
Value
58
-1
-5
int. limit.
14
70
12
13
6
-0.3
5.5
-0.3
Vcc
-0.3
5
1.3
2
4
-40 to 150
V
V
V
V
V
V
V
V
V
V
W
W
W
W
°C
Unit
V
V
V
PIN FUNCTIONS
Powerdip
11
10
9
18
7,8
2,3
12
SO20
12
11
10
20
8,9
2,3
13
NAME
COMP
INH
BOOT
SYNC
Vcc
OUT
VFB
DESCRIPTION
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.
A capacitor connected between this pin and the output allows to drive the
internal D-MOS.
Input/Output synchronization.
Unregulated DC input voltage
Stepdown regulator output.
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. An external
resistive divider is required for higher output voltages. For output voltage
less than 3.3V, see note ** and Figure 32.
Reference voltage externally available.
Signal ground
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)
16
4,5,6
13,14,15
1
18
4,5,6,7
14,15,16,17
1
V5.1
GND
OSC
3/16
L4973V3.3 - L4973V5.1 - L4973D3.3 - L4973D5.1
ELECTRICAL CHARACTERISTICS
( Refer to the test circuit,V
CC
= 24V; T
j
= 25
°
C, C
OSC
= 2.7nF;
R
OSC
= 20K
Ω
; unless otherwise specified)
•
= specifications referred to T
J
from 0 to 125°C.
Symbol
Parameter
Test Conditions
V
O
= V
REF
to 40V; I
O
= 3.5A
I
O
= 1A
I
O
= 0.5A to 3.5A
V
CC
= 8V to 55V
I
O
= 1A
I
O
= 0.5A to 3.5A
V
CC
= 8V to 40V
V
CC
= 10.5V
I
O
= 3.5A
V
CC
= 8V to 55V
V
O
= 5.1V; I
O
= 3.5A
V
O
= 3.3V; I
O
= 3.5A
V
i
= V
CC
+2V
RMS
V
O
= V
ref
; I
O
= 1A; f
ripple
= 100Hz
V
CC
= 8V to 55V
Min.
Typ.
Max.
55
5.1
5.1
5.1
3.36
3.36
3.36
0.15
4.5
90
85
100
5.15
5.20
5.25
3.393
3.427
3.46
0.22
0.35
5.5
Unit
V
V
V
V
V
V
V
Ω
Ω
A
%
%
KHz
dB
%
DYNAMIC CHARACTERISTICS
Input Voltage Range (*)
Output Voltage
L4973V5.1
Output Voltage
L4973V3.3
R
DSON
Maximum Limiting Current
Efficiency
Switching Frequency
Supply Voltage Ripple
Rejection
Switching Frequency Stability
vs, Supply Voltage
Reference Voltage
I
ref
= 0 to 20mA;
V
CC
= 8 to 55V
I
ref
= 0mA;
V
CC
= 8 to 55V
V
ref
= 0 to 5mA;
V
CC
= 0 to 20mA
•
•
•
•
•
•
8
5.05
5.00
4.95
3.326
3.292
3.26
4
η
90
60
110
∆f
sw
2
5
REFERENCE SECTION
•
5.025
4.950
5.1
5.1
5
2
6
65
45
22
5.175
5.250
10
10
25
100
60
30
V
V
mV
mV
mV
mA
µA
µA
Line Regulation
Load Regulation
Short Circuit Current
30
30
15
SOFT START
Soft Start Charge Current
Soft Start Discharge Current
INHIBIT
High Level Voltage
Low Level Voltage
I
source
High Level
I
source
Low Level
V
INH
= 3V
V
INH
= 0.8V
Duty Cycle = 50%
Duty Cycle = 0
V
CC
= 24V; V
INH
= 5V
V
CC
= 55V; V
INH
= 5V
•
•
•
•
3.0
10
10
16
15
4
2.7
100
150
0.8
50
50
6
4
200
300
V
V
µA
µA
mA
mA
µA
µA
V
V
µA
µA
DC CHARACTERISTICS
Total Operating Quiescent
Current
Quiescent Current
Total stand-by quiescent
current
ERROR AMPLIFIER
High Level Output Voltage
Low Level Output Voltage
Source Bias Current
Source Output Current
4/16
11.0
1
200
2
300
0.65
3
600
L4973V3 - L4973V5 - L4973D3 - L4973D5
ELECTRICAL CHARACTERISTICS
(continued)
Sink Output Current
Supply Voltage Ripple
Rejection
DC Open Loop Gain
Transconductance
V
COMP
= VFB
C
REF
=4.7µF 1-5mA load
current
R
L
=
∞
I
comp
= -0.1 to 0.1mA;
V
comp
= 6V
200
60
300
80
µA
dB
50
60
2.5
dB
mS
OSCILLATOR SECTION
Ramp valley
Ramp peak
Maximum Duty Cycle
Maximum Frequency
V
CC
= 8V
V
CC
= 55V
Duty Cycle = 0%; R
OSC
=
13KΩ; C
OSC
= 820pF;
V
CC
= 8V to 55V
V
CC
= 8V to 55V
I
source
= 3mA
no load, V
sync
= 4.5V
3.5
0.15
4
0.20
0.25
4.5
0.35
0.9
0.45
0.78
1.9
9
95
0.85
2.1
9.6
97
0.92
2.3
10.2
500
V
V
V
%
KHz
SYNC FUNCTION
High Input Voltage
Low Input Voltage
Slave Sink Current
Master Output Amplitude
Output Pulse Width
(*) Pulse testing with a low duty cycle.
(**) The maximum power dissipation of the package must be observed.
V
V
mA
V
µs
Figure 1. Evaluation Board Circuit
V
CC
(DIP18)
R2
7,8
1
17
12
L4973
11
10
9
C8
L1
V
O
R3
C1
C2
C7
16
4,5,6
2,3
13,14,15
C3
C4
C5
R1
C6
D1
3x
C0
C12
R4
D97IN515B
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 K
OOL
µ
77310 - 40 Turns - 0.9mm
R1=9.1K
R2=20K
D1=GI SB560
L4973 V3.3
V
O
(V)
3.3
5.1
12
15
18
24
R3(KΩ)
0
2.7
12
16
20
30
4.7
4.7
4.7
4.7
4.7
R4(KΩ)
V
O
(V)
5.1
12
15
18
24
L4973 V5.1
R3(KΩ)
0
6.2
9.1
12
18
4.7
4.7
4.7
4.7
R4(KΩ)
5/16
PCB Design
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