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L4957A
Up to 5A ULDO linear regulator
General features

1.5V, 1.8V, 2.5V and 3.3V fixed output voltage 3V to 14V input voltage range 200m RDS(on) typical @ tJ = 125C 0.6V max. drop-out at 2A Excellent load regulation 0.6mA quiescent current at any load Short circuit protection Thermal shutdown
3 1
D2PAK
Description
The L4957AD devices are Ultra Low Drop Output linear regulators with an internal N-channel MOSFET of 200m particulary suitable for low voltage/low dropout applications. Operating with a input voltage from 3V to 14V they are capable to deliver up to 5A. The devices are ideal for use as one of the suppliesrequired by processor, for example they are the cost effective and efficient solution for conversion from 3.3V (rail bus) to 2.5V @ 2.5A or to 1.5V with high current rating. Fast response transient minimise the output capacitor value. A minimum of 22F assures the stability in all load conditions. The on-chip trimming technique offers a tighter voltage reference tolerance (with 2% including line and load variation) beside to ensure a controlled short circuit current. Thermal shutdown provides protection against overload conditions that creates excessive junction temperature.
Applications

Mother boards Processor I/O & supplies Low voltage memory & chip set supplies Graphic & sound cards Low voltage logic supplies Post regulator for SMPS
Order codes
Part number Tube L4957AD1.5 L4957AD1.8 L4957AD2.5 L4957AD3.3 April 2006 Rev 6 Tape and Reel L4957AD1.5TR L4957AD1.8TR L4957AD2.5TR L4957AD3.3TR 1/12
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Contents
L4957A
Contents
1 2 Block diagram and typical application . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 2.2 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 3.2 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 5 6
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
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L4957A
Block diagram and typical application
1
Block diagram and typical application
Figure 1. Block diagram
VIN 10F
IN 1 CHARGE PUMP
VREF
CURRENT LIMIT
PRE REGULATOR
+ -
E/A
BUFFER
POWER DMOS 200m OUT RX 3 VOUT 22F
THERMAL SHUTDOWN
RY 2 GND
D00IN1108A
Figure 2.
Typical application
3V to 14V
IN
1
3
OUT
VOUT
L4957AD
C1 2 GND
D00IN1107B
C2
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Pin description
L4957A
2
2.1
Pin description
Pin connection
Figure 3. Pin connection (top view)
3 2 1 GND
OUT
IN
D98IN933A
D2PAK
2.2
Pin description
Table 1. Pin description
Name 1 2 3 Pin N IN GND OUT Description Unregulated input voltage; this pin must be bypassed with a capacitor larger than 10F. To connect to Ground to get 1.5V, 1.8V, 2.5V or 3.3V output. Regulated output voltage. A minimum bypass capacitor of 22F is required to insure stability.
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L4957A
Maximum ratings
3
3.1
Maximum ratings
Absolute maximum ratings
Table 2. Absolute maximum ratings
Symbol VIN TJ TSTG Supply input voltage Junction temperature Storage temperature Parameter Value 16 -40 to +150 -40 to +150 Unit V C C
3.2
Thermal data
Table 3. Thermal data
Symbol RthJC RthJA Parameter Maximum thermal resistance junction-case Maximum thermal resistance junction-ambient Thermal Shutdown Thermal Hysteresis Typ. Typ. Value 3 60 150 29 Unit C/W C/W C C
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Electrical characteristics
L4957A
4
Electrical characteristics
Table 4. Electrical Characteristcs (TJ = 25C, VIN = 5V, unless otherwise specified)
Symbol VIN VO Parameter Operating Supply Voltage Output Voltage 3.15V < VIN < 5.25V; IO = 0.1A VIN = 3.3V 5%; 0.1A < IO < 5A (1) VIN = 3.3V 5% IO = 0.1A VIN = 5V 5% VIN = 3.3V 5% (0.1A < IO< 4.5A) (1) VIN = 5V 5% 0.1A < IO< 5A VIN = 3.3V 5% IO = 0.1A VIN = 5V 5% VIN = 3.3V 5% (0.1A < IO< 2.2A) (1) VIN = 5V 5% 0.1A < IO< 5A VIN = 5V 5% IO = 0.1A VIN = 5V 5% 0.1A < IO< 5A (1) RDS(on) IO IQ Drain-Source ON Resistance Current Limiting Quiescent Current Ripple Rejection
(1) (1)
Test condition
Min 3 1.485 1.47 1.782
Typ
Max 14
Unit V V V V
1.5 1.5 1.8
1.515 1.53 1.818
1.764
1.8
1.836
V
2.475
2.5
2.525
V
2.45 3.267 3.234
2.5 3.3 3.3
2.55 3.333 3.366 300
V V V m A mA dB
5.1
6.3 0.6
7.5 2
3V < VIN< 14V (1) f = 120Hz, IO = 1A VIN = 5V VIN = 2V PP 60
75
1. Specifications referred to TJ from 0C to +125C.
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L4957A
Electrical characteristics
Figure 4.
5 O u tp u t V o lta g e D e v ia tio n [m V ] 4 .5 4 3 .5 3 2 .5 2 1 .5 1 0 .5 0 -4 0 -2 0
Line regulation vs. junction temperature
Figure 5.
Load regulation
O u tp u t V o lta g e D e v ia tio n [m V ]
5 4 3 2 1 0 -1 -2 -3 -4
3 V < V in < 6 .5 V Io u t = 1 0 m A
V in = 5 V T j = 2 5 C ( P u ls e d te c h n iq u e h a s b e e n u s e d )
V o u t = 1 .5 V
0
20
40
60 80 100 120 140 160 T j [ C ]
-5
0
1
2 Io u t [A ]
3
4
5
Figure 6.
Maximum output current vs. junction temperature
Figure 7.
DC operating area
O u tp u t C u rre n t [A ] 10 9 8 7 6 5 4 3 2 1 0 -4 0 -2 0 0 20 40 60 80 100 120 140 160 T j [ C ] (V in -V o u t) > 2 V p in 2 = G N D
O u tp u t C u r re n t [A ] 8 7 6
R d son lim it V in > 2 .8 V T j= 1 2 5 C C u rre n t L im ita tio n P o w e r D issip a tio n L im it T c =2 5 C P d m a x= 40 W
5 4 3
D C O p e ra tin g A re a T c= 7 0C P dm a x= 22 W
2 1 0 0 1 2 3 4 5 (V in - V o u t) [V ] 6 7 8
* P u ls e d te c n iq u e h a s b e e n u s e d
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Electrical characteristics Figure 8. Ripple rejection vs. frequency Figure 9.
L4957A Output voltage vs. output current (VOUT = 1.5V)
D00IN1109
R ip p le R e je c tio n [d B ] 100 90 80 70 60 50 40 30 20 10 0 10 100 1k F re q u e n c y [ H z ] 10k 10 0 k
C in = 2 2 u F C o u t= 2 2 u F V o u t= 1 .5 V V in m in = 3 V Io u t= 5 A V rip p le = 3 V p - p V r ip p le = 0 .5 V p -p
VOUT (V)
6.3
IOUT(A)
Figure 10. Maximum output current vs. junction temperature
Io [A ] 5 4 .5 4 3 .5 3 2 .5 2 1 .5 1 0 .5 0 0 0 .2 0 .4 0 .6 0 .8 1 1 .2 1 .4 1 .6 1 .8 2 V = V in - V o m a x im u m R o n lim its T j = 2 5 C Tj = 125C Tj = 100C
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L4957A
Package mechanical data
5
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK(R) 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
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Package mechanical data Table 5. D 2PAK Mechanical data
mm. Dim. Min A A1 A2 B B2 C C2 D E G L L2 L3 R V2 0 4.30 2.49 0.03 0.70 1.25 0.45 1.21 8.95 10.00 4.88 15.00 1.27 1.40 0.40 8 0 1.40 0.60 1.36 9.35 10.28 5.28 15.85 1.40 1.75 Typ Max 4.60 2.69 0.23 0.93 Min 0.169 0.098 0.001 0.027 0.049 0.017 0.047 0.352 0.393 0.192 0.590 0.050 0.055 0.016 0.055 Typ inch
L4957A
Max 0.181 0.106 0.009 0.037
0.024 0.054 0.368 0.405 0.208 0.624 0.055 0.069
8
Figure 11. Package dimensions
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L4957A
Revision history
6
Revision history
Table 6. Revision history
Date 12-Feb-2002 20-Apr-2006 Revision 5 6 Changes Removed the L4957AV part number and its references in the whole document New template
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L4957A
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