LTC1798 Series
1
The LTC
1798/LTC1798-2.5/LTC1798-3/LTC1798-4.1/
LTC1798-5 are micropower bandgap references that com-
bine high accuracy and low drift with very low supply
current and small package size. The combination of ultralow
quiescent current and low dropout voltage of only 200mV
(max) makes them ideal for battery-powered equipment.
The output voltage is set by an external resistor divider for
the adjustable LTC1798.
This series of references uses curvature compensation to
obtain low temperature coefficient and trimmed thin-film
resistors to achieve high output accuracy. These refer-
ences can source up to 10mA and sink up to 2mA, making
them ideal for precision regulator applications. They are
stable without an output bypass capacitor, but are also
stable with capacitance up to 1
F. This feature is important
in critical applications where PC board space is a premium
and fast settling is demanded.
The LTC1798 series references provided power dissipa-
tion advantages over shunt references. In addition to
supply current, shunt references must also idle the entire
load current to operate.
The LTC1798 series is available in the SO-8 package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
s
200mV Max Dropout at 10mA Output Current
s
4
A Typical Quiescent Current
s
0.15% Max Initial Accuracy
s
No Output Capacitor Required
s
Output Sources 10mA, Sinks 2mA
s
40ppm/
C Max Drift
s
Voltage Options: 2.5V, 3V, 4.1V, 5V and Adjustable
APPLICATIO S
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FEATURES
DESCRIPTIO
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TYPICAL APPLICATIO
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Micropower Low
Dropout References
s
Battery-Powered Systems
s
Handheld Instruments
s
Precision Power Supplies
s
A/D and D/A Converters
2.5V Battery-Powered Reference
LTC1798-2.5 Temperature Drift
LTC1798-2.5
OUT
IN
GND
4
2
2.7V
TO 12.6V
6
2.5V
1798 TA01
0.1
F
TEMPERATURE (
C)
40
20
0
20
40
60
80
100
REFERENCE VOLTAGE CHANGE (mV)
1798 TA02
4
3
2
1
2
1
3
4
0
LTC1798 Series
2
ABSOLUTE AXI U
RATI GS
W
W
W
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PACKAGE/ORDER I FOR ATIO
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U
W
(Note 1)
ELECTRICAL CHARACTERISTICS
Supply Voltage ....................................................... 13V
Input Voltages .......................................... 0.3v to 13V
Output Voltages ........................................ 0.3V to 13V
Output Short-Circuit Duration .......................... Indefinite
Operating Temperature Range
(Note 2) ........................................... 40
C to 100
C
Specified Temperature Range ..................... 0
C to 70
C
Storage Temperature Range (Note 3) ... 65
C to 150
C
Lead Temperature (Soldering, 10 sec)................. 300
C
LTC1798CS8
LTC1798CS8-2.5
LTC1798CS8-3
LTC1798CS8-4.1
LTC1798CS8-5
T
JMAX
= 125
C,
JA
= 190
C/W
ORDER PART
NUMBER
Consult factory for parts specified with wider operating temperature range.
S8 PART MARKING
1798
179825
17983
179841
17985
1
2
3
4
8
7
6
5
TOP VIEW
DNC*
DNC*
OUT
DNC*
*DNC
IN
**DNC/FB
GND
S8 PACKAGE
8-LEAD PLASTIC SO
* CONNECTED INTERNALLY. DO NOT
CONNECT EXTERNAL CIRCUITRY TO
THESE PINS
** DNC FOR LTC1798-2.5/LTC1798-3/
LTC1798-4.1/LTC1798-5, FB FOR LTC1798
OUTPUT
TEMPERATURE
TEMPERATURE
PACKAGE TYPE
VOLTAGE
RANGE
ACCURACY
COEFFICIENT
SO-8 (S8)
(V)
(
C)
(%)
(ppm/
C)
ORDER NUMBER
PART MARKING
2.5
0 to 70
0.15
40
LTC1798CS8-2.5
179825
3
0 to 70
0.15
40
LTC1798CS8-3
17983
4.096
0 to 70
0.15
40
LTC1798CS8-4.1
179841
5
0 to 70
0.15
40
LTC1798CS8-5
17985
Adjustable
0 to 70
0.4
40
LTC1798CS8
1798
AVAILABLE OPTIO S
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The
q
denotes specifications which apply over the full specified temperature range, otherwise specifications are at T
A
= 25
C.
V
IN
= V
OUT(NOMINAL)
+ 0.2V, I
OUT
= 0mA unless otherwise noted. FB = OUT for the LTC1798.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Input Voltage Range
q
12.6
V
I
IN
Input Current
FB = OUT for LTC1798
4.0
6.5
A
q
8.5
A
V
OUT
Output Voltage (Note 4)
LTC1798, FB = OUT
2.3755
2.385
2.3945
V
LTC1798 ADJ
0.4
0.4
%
LTC1798-2.5
2.4963
2.5
2.5037
V
LTC1798-3
2.9955
3
3.0045
V
LTC1798-4.1
4.090
4.096
4.102
V
LTC1798-5
4.9925
5
5.0075
V
LTC1798 All Fixed Options
0.15
0.15
%
LTC1798 Series
3
The
q
denotes specifications which apply over the full specified temperature range, otherwise specifications are at T
A
= 25
C.
V
IN
= V
OUT(NOMINAL)
+ 0.2V, I
OUT
= 0mA unless otherwise noted. FB = OUT for the LTC1798.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
e
n
Output Voltage Noise (Note 5)
0.1Hz
f
10Hz
8
ppm
P-P
TC
Output Voltage Temp Coefficient (Note 6)
T
MIN
T
J
T
MAX
q
15
40
ppm/
C
V
OUT
/V
IN
Line Regulation
V
IN
= (V
OUT(NOMINAL)
+ 0.2V) to 12.6V
q
30
120
ppm/V
V
OUT
/I
OUT
Load Regulation (Note 7)
Sourcing 0mA to 10mA
q
0.1
0.3
mV/mA
Sinking 0mA to 2mA
1.75
4.0
mV/mA
q
6.5
mV/mA
I
SC
Short-Circuit Output Current
V
OUT
Shorted to GND
20
40
mA
V
OUT
Shorted to V
IN
2
4
mA
V
DO
Dropout Voltage (Note 8)
I
OUT
= 0,
V
OUT
0.1%
q
100
mV
I
OUT
= 10mA,
V
OUT
0.1%
q
200
mV
V
HYST
Output Hysteresis (Note 9)
T = 40
C to 85
C
200
ppm
T = 0
C to 70
C
50
ppm
I
FB
FB Pin Input Current
LTC1798, OUT = FB
10
nA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: The LTC1798 is guaranteed functional over the operating
temperature range of 40
C to 100
C.
Note 3: If the part is stored outside of the specified operating temperature
range, the output may shift due to hysteresis.
Note 4: ESD (Electostatic Discharge) sensitive device. Extensive use of
ESD protection devices are used internal to the LTC1798, however, high
electrostatic discharge can damage or degrade the device. Use proper ESD
handling precautions.
Note 5: Peak-to-peak noise is measured with a single pole highpass filter
at 0.1Hz and 2-pole lowpass filter at 10Hz.
Note 6: Temperature coefficient is the change in output voltage divided by
the nominal output voltage divided by the specified temperature range.
Note 7: Load regulation is measured on a pulse basis from no load to the
specified load current. Output changes due to die temperature change
must be taken into account separately.
Note 8: Dropout voltage is (V
IN
V
OUT
) when V
OUT
falls to 0.1% below its
nominal value at V
IN
= V
OUT
+ 0.5V.
Note 9: Hysteresis in output voltage is created by package stress that
differs depending on whether the IC was previously at a higher or lower
temperature. Output voltage is always measured at 25
C, but the IC is
cycled hot or cold before successive measurements. Hysteresis is not
normally a problem for operational temperature excursions where the
instrument might be stored at high or low temperature.
LTC1798-2.5* Dropout Voltage
vs Output Source Current
LTC1798-2.5*
Input Current vs Temperature
LTC1798 Series Output Short-
Circuit Current vs Temperature
*Similar performance characteristics can be expected for all voltage options.
ELECTRICAL CHARACTERISTICS
TYPICAL PERFOR A CE CHARACTERISTICS
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OUTPUT SOURCE CURRENT (mA)
DROPOUT VOLTAGE (mV)
100
90
80
70
60
50
40
30
20
10
0
0
1
10
100
1798 G01
0.1
T
A
= 25
C
TEMPERATURE (
C)
50 25
INPUT CURRENT (
A)
150
1798 G02
0
25
50
75
100 125
8
7
6
5
4
3
2
1
0
V
IN
= 2.7V
TEMPERATURE (
C)
50 25
OUTPUT SHORT-CIRCUIT CURRENT (mA)
150
1798 G03
0
25
50
75
100 125
70
60
50
40
30
20
10
5
0
T
A
= 25
C
V
IN
= V
OUT(NOM)
+ 0.2V
OUTPUT
SHORTED
TO V
IN
OUTPUT
SHORTED
TO GND
LTC1798 Series
4
TYPICAL PERFOR A CE CHARACTERISTICS
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W
LTC1798-2.5* Output Short-Circuit
Current vs Input Voltage
LTC1798 Series
Load Regulation
LTC1798-2.5* Output Short-Circuit
Current vs Input Voltage
LTC1798-2.5*
Output Voltage vs Input Voltage
LTC1798-2.5*
Input Current vs Input Voltage
LTC1798-2.5 PSRR vs Frequency
LTC1798-2.5 0.1Hz to 10Hz Noise
LTC1798-5 Input Current vs Input
Voltage in Dropout
LTC1798-2.5 Input Current vs Input
Voltage in Dropout
INPUT VOLTAGE (V)
2
OUTPUT SHORT-CIRCUIT CURRENT (mA)
25
20
15
10
5
0
4
6
8
10
1258-G04
12
14
T
A
= 25
C
OUTPUT SHORTED
TO V
IN
INPUT VOLTAGE (V)
2
OUTPUT SHORT-CIRCUIT CURRENT (mA)
42
41
4
6
8
10
1798 G05
12
14
T
A
= 25
C
OUTPUT SHORTED
TO GND
OUTPUT CURRENT (mA)
V
OUT
FROM NO LOAD (mV)
5
4
3
2
1
0
1
2
3
4
5
0
1
10
100
1798 G06
0.1
T
A
= 25
C
V
IN
= V
OUT(NOM)
+ 0.2V
SINKING
SOURCING
INPUT VOLTAGE (V)
2
OUTPUT VOLTAGE (V)
2.5010
2.5005
2.5000
2.4995
4
6
8
10
1798 G07
12
14
T
A
= 25
C
INPUT VOLTAGE (V)
2
INPUT CURRENT (
A)
7
6
5
4
4
6
8
10
1798 G08
12
14
T
A
= 25
C
FREQUENCY (Hz)
POWER SUPPLY REJECTION RATIO (dB)
60
50
40
30
20
10
0
10
1k
10k
1798 G09
100
V
IN
= 2.7V
5
V/DIV
1798 G10
1SEC/DIV
V
IN
= 2.7V
INPUT VOLTAGE (V)
0
1
2
3
4
5
6
7
8
9
10
INPUT CURRENT (
A)
1798 G11
1400
1200
1000
800
600
400
200
0
T
A
= 55
C
T
A
= 25
C
T
A
= 125
C
INPUT VOLTAGE (V)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
INPUT CURRENT (
A)
1798 G12
250
200
150
100
50
0
T
A
= 25
C
T
A
= 55
C
T
A
= 125
C
LTC1798 Series
5
DNC (Pins 1, 5, 7, 8): Do Not Connect. Connected
internally for post package trim. These pins must be left
unconnected.
IN (Pin 2): Positive Supply. Bypassing with a 0.1
F
capacitor is recommended if the output loading changes.
(V
OUT
+ 0.2V)
V
IN
12.6V.
DNC (Pin 3): (LTC1798-2.5/LTC1798-3/LTC1798-4.1/
LTC1798-5) Do Not Connect. Connected internally for
post package trim. This pin must be left unconnected.
FB (Pin 3): (LTC1798) Resistor Divider Feedback Pin.
Connect a resistor divider from OUT to GND and the center
tap to FB. This pin sets the output potential.
V
V
R
R
R
OUT
=
+
2 385
1
2
2
.
; R1 is connected from OUT
to FB and R2 from FB to GND. Selecting R2
10k will
make I
OUT
< 250
A.
GND (Pin 4): Negative Supply or Ground Connection.
OUT (Pin 6): Reference Output. The output can source up
to 10mA and sink up to 2mA. It is stable with output bypass
capacitor ranging from 0
F to 1
F.
+
IN
6
1798 BD
2
4
OUT
3 (LTC1798)
FB
2.385V
GND
R1
R2
NOTE: R1 AND R2 ARE NOT CONNECTED FOR LTC1798
BLOCK DIAGRA
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PI FU CTIO S
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