L5973D
2.5 A switch step down switching regulator
Features
■
■
■
■
■
■
■
■
■
■
■
■
■
2.5 A internal switch
Operating input voltage from 4 V to 36 V
3.3 V / (±2%) reference voltage
Output voltage adjustable from 1.235 V to 35 V
Low dropout operation: 100 % duty cycle
250 kHz internally fixed frequency
Voltage feedforward
Zero load current operation
Internal current limiting
Inhibit for zero current consumption
Synchronization
Protection against feedback disconnection
Thermal shutdown
Applications
■
■
■
■
Consumer: STB, DVD, TV, VCR, car radio,
LCD monitors
Networking: XDSL, modems, DC-DC modules
Computer: printers, audio/graphic cards, optical storage, hard disk drive
Industrial: changers, car battery, DC-DC converters
Description
Figure 1.
Test application circuit
VIN = 4.4V to 35V
3.3V
VREF
VCC
C1
10 µF
35V
CERAMIC
C4
22nF
SYNC.
COMP
C3
220pF
R3
4.7K
6
8
2
L5973D
4
INH
3 7
GND
1
5
HSOP8 exposed pad
The L5973D is a step down monolithic power switching regulator with a minimum switch current limit of 2.5 A so it is able to deliver more than 2 A
DC current to the load depending on the application conditions.
The output voltage can be set from 1.235 V to
35 V. The high current level is also achieved thanks to an SO8 package with exposed frame, that allows to reduce the Rth(j-amb) down to approximately 40 °C/W.
The device uses an internal P-channel D-MOS transistor (with a typical Rdson of 250 m
Ω) as switching element to minimize the size of the external components.
An internal oscillator fixes the switching frequency at 250 kHz.
Having a minimum input voltage of 4 V only, it is particularly suitable for 5 V 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.
OUT
FB
L1 15
µH
D1
STPS340U
R1
5.6K
R2
3.3K
VOUT=3.3V
C2
330
µF
10V
January 2008 Rev 16
D03IN1439
1/17 www.st.com
17
7
8
9
5
6
3
4
Contents
Contents
1
2
L5973D
Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1
Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Order code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2/17
L5973D Pin settings
Figure 2.
Pin connection (top view)
OUT
SYNC
INH
COMP
1
2
3
4
D98IN955
6
5
8
7
VCC
GND
VREF
FB
Table 1.
N°
1
2
5
6
7
8
3
4
Pin description
Type
OUT
SYNC
INH
COMP
FB
VREF
GND
VCC
Description
Regulator output.
Master/slave synchronization.
A logical signal (active high) disables the device. If INH not used the pin must be grounded. When it is open an internal pull-up disable the device.
E/A output for frequency compensation.
Feedback input. Connecting directly to this pin results in an output voltage of 1.23 V. An external resistive divider is required for higher output voltages.
3.3 V V
REF
. No cap is requested for stability.
Ground.
Unregulated DC input voltage.
3/17
Electrical data L5973D
Table 2.
Symbol
Absolute maximum ratings
Parameter
V
8
V
1
I
1
V
4
, V
5
V
3
V
2
P
TOT
T
J
T
STG
Input voltage
Output DC voltage
Output peak voltage at t = 0.1
µs
Maximum output current
Analog pins
INH
SYNC
Power dissipation at T
A
≤ 60 °C
Operating junction temperature range
Storage temperature range
Value
40
-1 to 40
-5 to 40 int. limit.
4
-0.3 V to V
CC
-0.3 to 4
2.25
-40 to 150
-55 to 150
V
V
W
°C
°C
Unit
V
V
V
Table 3.
Symbol
Thermal data
Parameter
R thJA
Maximum thermal resistance junction-ambient
1.
Package mounted on board
HSOP8
Exposed Pad
40
(1)
Unit
°C/W
4/17
L5973D Electrical characteristics
Table 4.
Symbol
Electrical characteristics
( T
J
= 25 °C, V
CC
= 12 V, unless otherwise specified)
Parameter Test condition
V
CC
R
DS(on)
I l
Operating input voltage range
Mosfet on
Resistance
Maximum limiting current
V o
= 1.235 V; I o
= 2 A
V
CC
= 4.4 V to 36 V
(1)
(1)
Min
4
2.5
(1) f s
Switching frequency
212
225
0 Duty cycle
Dynamic characteristics (see test circuit ).
V
5
Voltage feedback
4.4 V < V
CC
< 36 V,
20 mA < I
O
< 2 A
V
O
= 5 V, V
CC
= 12 V
(1)
Typ Max Unit
0.250
0.5
3
36
3.5
250 280
250 275
100
1.220
1.235
1.25
1.198
1.235
1.272
90
V
Ω
A kHz kHz
% h Efficiency
DC characteristics
I qop
Total operating quiescent current
(1)
3 5
V
V
% mA
I q
I qst-by
Quiescent current
Total stand-by quiescent current
Duty Cycle = 0;
V
FB
= 1.5 V
V inh
> 2.2 V
V
CC
= 36 V;
V inh
> 2.2 V
(1)
(1)
50
80
2.5
100
150 mA
µA
µA
Inhibit
INH threshold voltage
Device ON
Device OFF 2.2
0.8
V
V
Error amplfier
V
OH
V
OL
I o source
I o sink
High level output voltage
Low level output voltage
Source output current
Sink output current
VFB = 1 V
VFB = 1.5 V
V
COMP
= 1.9 V;
V
FB
= 1 V
V
COMP
= 1.9 V;
V
FB
= 1.5 V
3.5
200
1
300
1.5
0.4
V
V
µA mA
5/17
Electrical characteristics L5973D
Table 4.
Symbol
Electrical characteristics (continued)
( T
J
= 25 °C, V
CC
= 12 V, unless otherwise specified)
Parameter Test condition
I b gm
Source bias current
DC open loop gain R
L
=
∞
Transconductance
I comp
= -0.1 mA to
0.1 mA
V
COMP
= 1.9 V
Min
50
Sync function
High input voltage
Low input voltage
Slave sink current
V
CC
= 4.4 V to 36 V
V
CC
= 4.4 V to 36 V
V sync
= 0.74 V
(2)
V sync
= 2.33 V
2.5
0.11
0.21
Master output amplitude
I source
= 3 mA 2.75
Output pulse width no load,
V sync
= 1.65 V
Typ Max Unit
2.5
57
4
µA dB
2.3
3
0.20
0.35
V
REF
0.74
0.25
0.45
mS
V
µs
V
V mA mA
Reference section
Reference voltage 3.234
3.3
3.366
V
Line regulation
Load regulation
Short circuit current
I
REF
= 0 to 5 mA
V
CC
= 4.4 V to 36 V
I
REF
= 0 mA
V
CC
= 4.4 V to 36 V
I
REF
= 0 to 5 mA
(1)
3.2
10
3.3
5
8
18
3.399
10
15
30
V mV mV mA
1.
Specification Referred to T
J
from -40 to 125 °C. Specification over the -40 to +125 T
J
Temperature range are assured by design, characterization and statistical correlation.
2.
Guaranteed by design.
6/17
L5973D Typical characteristics
1.8
1.6
1.4
1.2
-50
Figure 3.
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
Vcc = 12V
Vo = 3.3V
10
Tj = 25°C
Tj = 125°C
20
Vcc (V)
30
Figure 4.
Shutdown current vs junction temperature
Ishd ( µA)
70
60
50
40
Vcc = 12V
40
30
-50 0 50
Tj (°C)
100 150
Figure 5.
Output voltage vs junction temperature
Vo (V)
1.25
1.24
1.23
1.22
Vcc = 12V
Vcc=12V
1.21
1.2
-50 0 50
Tj (°C)
100 150
Figure 6.
Switching frequency vs junction temperature
Fsw (KHz)
260
250
240
230
220
-50
Vcc = 12V
Vo = 3.3V
0 50
Tj (°C)
100 150
Figure 7.
Quiescent current vs junction temperature
Iq (mA)
2
Vcc = 12V
DC = 0%
0 50
Tj (°C)
100 150
7/17
Typical characteristics L5973D
Figure 8.
Junction temperature vs output current
Tj(°C)
120
110
100
90
80
70
60
50
40
30
Vin=5V
Tamb=25°C
Vo=3.3V
Vo=2.5V
Vo=1.8V
20
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6
Io(A)
Figure 9.
Junction temperature vs output current
Tj (°C)
120
110
100
90
80
Vin=12V
Tamb=25°C
Vo=5V
Vo=3.3V
Vo=2.5V
70
60
50
40
30
20
0.2 0.4 0.6 0.8
1 1.2 1.4 1.6 1.8
2 2.2 2.4 2.6
Io (A)
Figure 10.
Efficiency vs output current Figure 11.
Efficiency vs output current
95
93
91
89
87
85
83
81
79
77
75
73
71
69
67
Vo=2.5V
Vo=1.8V
Vin=5V
Vo=3.3V
0.1
0.3 0.5 0.7
0.9 1.1
1.3 1.5 1.7
1.9
2.1 2.3
Io (A)
91
89
87 Vo=5V
85
83
81
79
77
75
Vo=3.3V
Vo=2.5V
73
71
Vin=12V
69
67
65
0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7
1.9 2.1 2.3
Io (A)
8/17
L5973D Application circuit
In figure 6 is shown the demonstration board application circuit, where the input supply voltage, V
CC
, can range from 4 V to 25 V due to the rated voltage of the input capacitor and the output voltage is adjustable from 1.235 V to V
CC
.
Figure 12.
Demonstration board application circuit
VIN = 4.4V to 25V
3.3V
VREF
VCC
C1
10
µF
25V
CERAMIC
6
C4
22nF
SYNC.
COMP
C3
220pF
R3
4.7K
8
2
4
INH
L5973D
3 7
GND
1
5
OUT
FB
L1 15
µH
D1
STPS2L25U
R1
5.6K
VOUT=3.3V
C2
330
µF
6.3V
R2
3.3K
D03IN1440
Table 5.
Component list
Reference Part number
C4
R1
R2
R3
C1
C2
C3
D1
L1
GRM32DR61E106KA12L
POSCAP 6TPB330M
C1206C221J5GAC
C1206C223K5RAC
STPS2L25U
DO3316P-153
Description
10
µF, 25 V
330
µF, 6.3 V
220 pF, 5%, 50 V
22 nF, 10%, 50 V
5.6 K, 1%, 0.1 W 0603
3.3 K, 1%, 0.1 W 0603
4.7 K, 1%, 0.1 W 0603
2 A, 25 V
15
µH, 3 A
Manufacturer
Murata
Sanyo
KEMET
KEMET
Neohm
Neohm
Neohm
ST
COILCRAFT
9/17
Application circuit
Figure 13.
PCB layout (component side)
L5973D
Figure 14.
PCB layout (bottom side)
Figure 15.
PCB layout (front side)
10/17
Below some graphs show the T
J
versus output current in different conditions of the input and output voltage and some efficiency measurements.
L5973D
Figure 16.
Positive buck-boost regulator
Application ideas
Figure 17.
Buck-boost regulator
Figure 18.
Dual output voltage with auxiliary winding
11/17
Application ideas L5973D
When an output voltage below the internal reference (1.235 V) is required, the circuit reported in the figure 18 can been used. In this case the minimum voltage reachable is 0.6 V and can be easily calculated with the following formula:
V
OUT
= V
FB
- [(V
REF
- V
FB
)x(R
2
/ R
1
)]
If the load is not present, a resistor connected between V
OUT
and GND is required in order to avoid that the voltage across C
OUT
increases.
The value of this resistor has to be calculated taking into account that the current flowing through this resistance has to be higher than the current flowing through R
2
.
Figure 19.
Output voltage below the 1.235 V internal voltage reference
12/17
L5973D
7 Package mechanical data
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
13/17
Package mechanical data
Table 6.
Dim
HSOP8 mechanical data mm
Min Typ h
L k ccc
E1
E2 e c
D
D1
E
A
A1
A2 b
0.00
1.25
0.31
0.17
4.80
3
5.80
3.80
2.31
0.25
0.40
Figure 20.
Package dimensions
4.90
3.1
6.00
3.90
2.41
1.27
Max
1.70
0.10
0.51
0.25
5.00
3.2
6.20
4.00
2.51
Min
0.50
0.0098
1.27
0.0157
0 ° (min), 8° (max)
0.10
0.0492
0.0122
0.0067
0.1890
0.118
0.2283
0.1496
0.091
L5973D inch
Typ
0.00
0.1929
0.122
0.095
Max
0.0669
0.0039
0.0201
0.0098
0.1969
0.126
0.2441
0.1575
0.099
0.0197
0.0500
0.0039
14/17
L5973D Order code
Table 7.
Order code
Part number
L5973D
L5973D013TR
Package
HSOP8 (Exposed pad)
HSOP8 (Exposed pad)
Packaging
Tube
Tape and reel
15/17
Revision history L5973D
pp
Table 8.
Date
Revision history
01-Nov-2005
22-May-2006
13-Nov-2006
26-Jan-2007
17-Oct-2007
24-Oct-2007
07-Jan-2008
Revision
10
11
12
13
14
15
16
Changes
Updated package information
Electrical characteristic
Table 4 updated, new application idea
Figure 19 added, new template
Typo in order codes
Updated
Table 4 on page 5
Updated
Section 5: Application circuit on page 9
Updated
Table 6 on page 14
Updated
Table 6 on page 14
16/17
L5973D
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