LT1118/LT1118-2.5
LT1118-2.85/LT1118-5
Low I
Q
, Low Dropout,
800mA, Source and Sink
Regulators Adjustable and
Fixed 2.5V, 2.85V, 5V Output
FEATURES
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■
■
■
■
■
■
■
DESCRIPTIO
Regulates While Sourcing or Sinking Current
Provides Termination for up to 27 SCSI Lines
600µA Quiescent Current
Ultralow Power Shutdown Mode
Current Limit and Thermal Shutdown Protection
Stable for Any C
LOAD
≥
0.22µF
Fast Settling Time
1V Dropout Voltage
APPLICATIO S
■
■
■
■
■
Active Negation SCSI Terminations
Computers
Disk Drives
CD-ROM
Supply Splitter
The LT
®
1118 family of low dropout regulators has the
unique capability of maintaining output regulation while
sourcing or sinking load current. The 2.85V output voltage
regulator is ideal for use as a Boulay termination of up to
27 SCSI data lines. The regulator maintains regulation
while both sourcing and sinking current, enabling the use
of active negation drivers for improved noise immunity on
the data lines. Regulation of output voltage is maintained
for TERMPWR voltages as low as 4.0V. When unloaded,
quiescent supply current is a low 600µA, allowing continu-
ous connection to the TERMPWR lines. An ultralow power
shutdown mode is also available on the SO-8 version. In
Shutdown the output is high impedance and supply cur-
rent drops to less than 10µA.
Current limits in both sourcing and sinking modes, plus
on-chip thermal shutdown make the circuit tolerant of
output fault conditions.
The LT1118 is available in 3-lead SOT-223 and 8-lead SO
packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
Load Transient Response
0.2V
IN
LT1118-2.85 OUT
GND
5V
2.2µF
1µF
CERAMIC
∆V
OUT
0V
– 0.2V
800mA
I
LOAD
1118 TA01
I
LOAD
0mA
– 400mA
U
1118 TA02.tif
U
U
1118fc
1
LT1118/LT1118-2.5
LT1118-2.85/LT1118-5
ABSOLUTE
AXI U RATI GS
Supply Voltage (V
CC
) ............................................... 15V
Input Voltage (Enable) ................................– 0.2V to 7V
Output Voltage ................................ – 0.2V to V
CC
+ 0.5V
Short-Circuit Duration ..................................... Indefinite
PACKAGE DESCRIPTIO
TOP VIEW
GND 1
NC 2
EN 3
FB 4
8 GND
7 IN
6 OUT
5 IN
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JC
= 15°C/W
ORDER
PART NUMBER
LT1118CS8
S8 PART
MARKING
1118
ORDER
PART NUMBER
LT1118CS8-2.5
LT1118CS8-2.85
LT1118CS8-5
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
PARAMETER
Quiescent Current (V
IN
)
Quiescent Current in Shutdown (V
IN
)
Enable Input Thresholds
Enable Input Current
Feedback Voltage
Output Voltage
LT1118
LT1118-2.5
LT1118-2.85
LT1118-5
CONDITIONS
V
EN
= 5V
V
EN
= 0V
Input Low Level
Input High Level
0V
≤
V
EN
≤
5V
No Load (25°C)
All Operating Conditions (Note 3)
No Load (25°C)
All Operating Conditions (Note 3)
No Load (25°C)
All Operating Conditions (Note 3)
No Load (25°C)
All Operating Conditions (Note 3)
●
●
●
●
●
●
●
●
●
2
U
U
W W
W
(Note 1)
Operating Temperature Range ..................... 0°C to 70°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
IN 1
OUT 2
GND 3
IN 4
8 EN
7 GND
6 GND
5 NC
TAB IS
GND
FRONT VIEW
3
2
1
IN
GND
OUT
S8 PACKAGE
8-LEAD PLASTIC SO
ST PACKAGE
3-LEAD PLASTIC SOT-223
T
JMAX
= 125°C,
θ
JC
= 15°C/W
T
JMAX
= 125°C,
θ
JC
= 15°C/W
S8 PART
MARKING
111825
111828
11185
ORDER
PART NUMBER
LT1118CST-2.5
LT1118CST-2.85
LT1118CST-5
ST PART
MARKING
111825
111828
11185
MIN
TYP
0.6
1
MAX
1
10
2
25
1.237
1.250
2.53
2.55
2.88
2.91
5.05
5.1
UNITS
mA
µA
V
V
µA
V
V
V
V
V
V
V
V
0.4
–1
1.213
1.200
2.47
2.45
2.82
2.79
4.95
4.90
1.4
1.4
1.225
1.225
2.5
2.5
2.85
2.85
5
5
1118fc
LT1118/LT1118-2.5
LT1118-2.85/LT1118-5
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
PARAMETER
Line Regulation (Note 4)
LT1118
LT1118-2.5
LT1118-2.85
LT1118-5
LT1118
LT1118-2.5
LT1118-2.85
LT1118-5
Dropout Voltage (Note 5)
FB Pin Bias Current
Minimum Output Voltage
Ripple Rejection
Load Transient Settling Time,
∆V
= 1%
Output Short-Circuit Current
I
SC+
I
SC–
LT1118
LT1118
f
RIPPLE
= 120Hz, V
IN
– V
OUT
= 2V
V
RIPPLE
= 0.5V
P-P
0mA
≤
I
L
≤
800mA, C
LOAD
= 1µF
– 400mA
≤
I
L
≤
0mA, C
LOAD
= 1µF
V
OUT
= 0V
V
OUT
= V
IN
No Load
No Load
800
●
CONDITIONS
I
L
= 0mA, 4.2V
≤
V
IN
≤
15V
I
L
= 0mA, 4.2V
≤
V
IN
≤
15V
I
L
= 0mA, 4.75V
≤
V
IN
≤
15V
I
L
= 0mA, 6.5V
≤
V
IN
≤
15V
0mA
≤
I
L
≤
800mA
– 400mA
≤
I
L
≤
0mA
0mA
≤
I
L
≤
800mA
– 400mA
≤
I
L
≤
0mA
0mA
≤
I
L
≤
800mA
– 400mA
≤
I
L
≤
0mA
0mA
≤
I
L
≤
800mA
– 400mA
≤
I
L
≤
0mA
I
L
= 100mA
I
L
= 800mA
●
●
●
●
●
●
●
●
●
●
●
●
MIN
TYP
MAX
6
6
6
10
6
6
12
12
12
12
25
25
UNITS
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
V
V
µA
V
dB
µs
µs
Load Regulation (Note 4)
0.85
1
0.35
60
80
5
5
1200
– 700
170
50
1.1
1.3
1
2.1
– 400
mA
mA
°C
µs
Thermal Shutdown Junction Temperature
Enable Turn-On Delay
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
Unless otherwide specified, testing done at V
CC
= 5V
(LT1118-2.5, LT1118-2.85) or V
CC
= 7V (LT1118-5). V
EN
= V
CC
. Output
C
LOAD
= 1µF, I
LOAD
= 0.
Note 3:
All operating conditions include the combined effects of load
current, input voltage and temperature over each parameter’s full range.
Note 4:
Load and line regulation are tested at a constant junction
temperature by low duty cycle pulse testing.
Note 5:
Dropout voltage is defined as the minimum input to output voltage
measured while sourcing the specified current.
1118fc
3
LT1118/LT1118-2.5
LT1118-2.85/LT1118-5
TYPICAL PERFORMANCE CHARACTERISTICS
Dropout Voltage vs Output Current
1.4
1.2
T
J
= 25°C
T
J
= 75°C
RIPPLE REJECTION (dB)
60
80
800mA
RIPPLE REJECTION (dB)
10mA
60
DROPOUT VOLTAGE
1
0.8
0.6
0.4
0.2
T
J
= 125°C
0
0
200
400
600
OUTPUT CURRENT (mA)
800
1118 G01
Output Impedance vs Frequency
10
NO CURRENT
100mA SOURCE
CURRENT (nA)
10mA SOURCE
0.1
300
250
200
150
100
50
450
400
RIPPLE REJECTION (dB)
1
Z
OUT
(mA)
0.01
100mA SINK
10mA SINK
0.001
10
2
10
3
10
4
10
5
FREQUENCY (Hz)
Input Current vs
Output Sink Current
2000
1750
GROUND PIN CURRENT (µA)
INPUT CURRENT (µA)
800
700
600
500
400
300
200
100
0
1500
1250
1000
750
500
250
0
0
50
100 150 200 250 300 350 400
OUTPUT SINK CURRENT (mA)
1118 G07
4
U W
Ripple Rejection vs Frequency
80
Ripple Rejection vs Frequency
400mA
10mA
40
NO LOAD
20
SOURCING CURRENT
0
10
100
1k
10k
FREQUENCY (Hz)
100k
1118 G02
40
NO LOAD
20
SINKING CURRENT
0
10
100
1k
10k
FREQUENCY (Hz)
100k
1118 G03
Feedback Current vs Temperature
80
Ripple Rejection vs Load Current
C
IN
= C
LOAD
= 1µF
60
350
40
20
10
6
1118 G04
0
–55 –35 –15
5
25 45
TEMP
65
85 105 125
1118 G05
0
–400 –200
0
200
400
LOAD CURRENT (mA)
600
800
1118 G06
Ground Pin Current vs
Output Source Current
0
400
200
600
OUTPUT SOURCING CURRENT (mA)
800
1118 G08
1118fc
LT1118/LT1118-2.5
LT1118-2.85/LT1118-5
PIN FUNCTIONS
IN:
Input Supply Pin. This pin should be decoupled with a
1µF or larger low ESR capacitor. The two IN pins on the
SO-8 package must be directly connected on the printed
circuit board to prevent voltage drops between the two
inputs. When used as a SCSI active termination, IN con-
nects to term power. When used as a supply splitter, IN is
also the positive supply output.
GND:
Ground Pin. The multiple GND pins on the SO-8
package are internally connected, but lowest load regula-
tion errors will result if these pins are tightly connected on
the printed circuit board. This will also aid heat dissipation
at high power levels.
EN:
TTL/CMOS Logic Input. A high level allows normal
operation. A low level reduces supply current to zero. This
pin is internally connected to V
IN
on 3-lead ST packaged
devices.
V
IN
1µF
EN
OPERATIO
Output Capacitor
The LT1118 family of voltage regulators require an output
capacitor for stability. The regulators are stable with
output capacitors larger than 0.2µF. Load transient re-
sponse is very sensitive to output capacitor value and
dielectric choice. Low ESR ceramic capacitors are the best
choice for fast settling to load transients. Output capaci-
tors between 0.2µF and 1µF give good performance in
most applications. Larger tantalum output capacitors may
be used to reduce load transient amplitudes. Larger ca-
pacitors should be paralleled with a 0.1µF ceramic capaci-
tor to maintain quick settling time performance and to
insure stability of the regulator control loop. Capacitors
larger than 10µF may be safely used with the regulators,
but little transient settling performance improvement re-
sults from their use.
U
U
U
U
OUT:
Regulated Output Voltage. Output can source or sink
current. Current limit for sourcing and sinking current is
provided to protect the device from fault conditons. The
output must have a low ESR output filter capacitor. C
OUT
≥
0.22µF to guarantee stability. A 0.1µF ceramic capacitor
may be needed in parallel with C
OUT
if the ESR of the main
C
OUT
is too high.
FB:
Feedback Pin. The feedback pin is used to program the
output voltage of the adjustable S8 part. The output
voltage range that can be achieved is 2.1V to 6.5V. The
output voltage is determined by the selection of feedback
resistors defined by the following formula:
V
OUT
= V
FB
(1 + R
1
/R
2
) + I
FB
R
1
LT1118 Adjustable
IN
LT1118
FB
R
2
1118 TA06
OUT
1µF
R
1
V
OUT
= V
FB
1 +
(
R
1
+ I
FB
R
1
R
2
)
GND
Worst case transient response of the LT1118 regulators
occurs at zero output current. In order to obtain the fastest
transient settling performance, the regulator output may
be preloaded with a small current. The preload current
reduces the regulator output impedance, reducing output
voltage settling time.
Thermal Considerations
The LT1118 regulators are packaged in plastic SOT-223
and fused lead S8 packages. These small footprint pack-
ages are unable to convectively dissipate the heat gener-
ated when the regulator is operating at high current levels.
In order to control die operating temperatures, the PC
board layout should allow for maximum possible copper
area at the ground pins of the LT1118. The ground pins
and the tab on the SOT-223 package are electrically and
1118fc
5
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