LTC1798 Series
Micropower Low
Dropout References
FEATURES
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DESCRIPTION
The LTC
®
1798/LTC1798-2.5/LTC1798-3/LTC1798-4.1/
LTC1798-5 are micropower bandgap references that
combine 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 references
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 1µF 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 dissipation
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.
200mV Max Dropout at 10mA Output Current
4µA Typical Quiescent Current
0.15% Max Initial Accuracy
No Output Capacitor Required
Output Sources 10mA, Sinks 2mA
40ppm/°C Max Drift
Voltage Options: 2.5V, 3V, 4.1V, 5V and Adjustable
APPLICATIONS
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Battery-Powered Systems
Handheld Instruments
Precision Power Supplies
A/D and D/A Converters
Available in the SO-8 Package
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
2.5V Battery-Powered Reference
LTC1798-2.5
2.7V
TO 12.6V
2
0.1µF
GND
4
1798 TA01
LTC1798-2.5 Temperature Drift
4
REFERENCE VOLTAGE CHANGE (mV)
3
2
1
0
–1
–2
–3
–4
–40
–20
0
20
40
60
TEMPERATURE (°C)
80
100
IN
OUT
6
2.5V
1798 TA02
1798fc
1
LTC1798 Series
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
*DNC 1
IN 2
**DNC/FB 3
GND 4
8
7
6
5
DNC*
DNC*
OUT
DNC*
Operating Temperature Range...................... 0°C to 70°C
Extended Commercial Operating
Temperature Range .................................. –40°C to 85°C
Junction Temperature ........................................... 110°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
q
JA
= 190°C/W
* 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
ORDER INFORMATION
LEAD FREE FINISH
LTC1798CS8#PBF
(OBSOLETE)
LTC1798CS8-2.5#PBF
LTC1798CS8-3#PBF
LTC1798CS8-4.1#PBF
LTC1798CS8-5#PBF
TAPE AND REEL
LTC1798CS8#TRPBF
LTC1798CS8-2.5#TRPBF
LTC1798CS8-3#TRPBF
LTC1798CS8-4.1#TRPBF
LTC1798CS8-5#TRPBF
PART MARKING
1798
179825
17983
179841
17985
PACKAGE DESCRIPTION
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
SPECIFIED TEMPERATURE RANGE
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
AVAILABLE OPTIONS
OUTPUT VOLTAGE
(V)
2.5
3
4.096
5
Adjustable
TEMPERATURE
RANGE
(ºC)
0 to 70
0 to 70
0 to 70
0 to 70
0 to 70
ACCURACY
(%)
0.15
0.15
0.15
0.15
0.4
TEMPERATURE
COEFFICIENT
(PPM/ºC)
40
40
40
40
40
PACKAGE STYLE
SO-8 (S8)
ORDER NUMBER
LTC1798CS8-2.5
LTC1798CS8-3
LTC1798CS8-4.1
LTC1798CS8-5
LTC1798CS8
PART MARKING
179825
17983
179841
17985
1798
1798fc
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LTC1798 Series
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
I
IN
V
OUT
PARAMETER
Input Voltage Range
Input Current
Output Voltage (Note 4)
FB = OUT for LTC1798
l
The
l
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.
CONDITIONS
l
MIN
TYP
4
MAX
12.6
6.5
8.5
2.3945
0.4
2.5037
3.0045
4.102
5.0075
0.15
40
120
0.3
4
6.5
UNITS
V
µA
µA
V
%
V
V
V
V
%
ppmP-P
ppm/°C
ppm/V
mV/mA
mV/mA
mV/mA
mA
mA
LTC1798, FB = OUT
LTC1798 ADJ
LTC1798-2.5
LTC1798-3
LTC1798-4.1
LTC1798-5
LTC1798 All Fixed Options
0.1Hz ≤ f ≤ 10Hz
T
MIN
≤ T
J
≤ T
MAX
V
IN
= (V
OUT(NOMINAL)
+ 0.2V) to 12.6V
Sourcing 0mA to 10mA
Sinking 0mA to 2mA
l
l
l
l
2.3755
–0.4
2.4963
2.9955
4.090
4.9925
–0.15
2.385
2.5
3
4.096
5
8
15
30
0.1
1.75
e
n
TC
V
OUT
/V
IN
V
OUT
/I
OUT
Output Voltage Noise (Note 5)
Output Voltage Temp Coefficient (Note 6)
Line Regulation
Load Regulation (Note 7)
I
SC
∆V
DO
V
HYST
I
FB
Short-Circuit Output Current
Dropout Voltage (Note 8)
Output Hysteresis (Note 9)
FB Pin Input Current
V
OUT
Shorted to GND
V
OUT
Shorted to V
IN
I
OUT
= 0,
∆V
OUT
≤ 0.1%
I
OUT
= 10mA,
∆V
OUT
≤ 0.1%
∆T
= –40°C to 85°C
∆T
= 0°C to 70°C
LTC1798, OUT = FB
l
l
20
2
40
4
100
200
200
50
10
mV
mV
ppm
ppm
nA
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:
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.
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LTC1798 Series
TYPICAL PERFORMANCE CHARACTERISTICS
LTC1798-2.5* Dropout Voltage
vs Output Source Current
100
90
DROPOUT VOLTAGE (mV)
80
70
60
50
40
30
20
10
0
0
0.1
1
10
OUTPUT SOURCE CURRENT (mA)
100
1798 G01
LTC1798-2.5*
Input Current vs Temperature
8
7
INPUT CURRENT (µA)
6
5
4
3
2
1
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
1798 G02
LTC1798 Series Output Short-Circuit
Current vs Temperature
70
OUTPUT SHORT-CIRCUIT CURRENT (mA)
60
50
40
30
20
10
5
0
–50 –25
0
OUTPUT
SHORTED
TO V
IN
25 50 75 100 125 150
TEMPERATURE (°C)
1798 G03
T
A
= 25°C
V
IN
= 2.7V
T
A
= 25°C
V
IN
= V
OUT(NOM)
+ 0.2V
OUTPUT
SHORTED
TO GND
LTC1798-2.5* Output Short-Circuit
Current vs Input Voltage
25
OUTPUT SHORT-CIRCUIT CURRENT (mA)
OUTPUT SHORT-CIRCUIT CURRENT (mA)
T
A
= 25°C
OUTPUT SHORTED
TO V
IN
42
LTC1798-2.5* Output Short-Circuit
Current vs Input Voltage
5
4
∆V
OUT
FROM NO LOAD (mV)
3
2
1
0
–1
–2
–3
–4
12
14
1798 G05
LTC1798 Series
Load Regulation
T
A
= 25°C
V
IN
= V
OUT(NOM)
+ 0.2V
SINKING
20
15
SOURCING
10
5
T
A
= 25°C
OUTPUT SHORTED
TO GND
41
2
4
6
8
10
INPUT VOLTAGE (V)
0
2
4
6
8
10
INPUT VOLTAGE (V)
12
14
1798 G04
–5
0
0.1
1
10
OUTPUT CURRENT (mA)
100
1798 G06
LTC1798-2.5*
Output Voltage vs Input Voltage
2.5010
T
A
= 25°C
7
LTC1798-2.5*
Input Current vs Input Voltage
60
POWER SUPPLY REJECTION RATIO (dB)
T
A
= 25°C
50
40
30
20
10
0
LTC1798-2.5
PSRR vs Frequency
V
IN
= 2.7V
OUTPUT VOLTAGE (V)
2.5005
INPUT CURRENT (µA)
12
14
1798 G07
6
2.5000
5
2.4995
2
4
6
8
10
INPUT VOLTAGE (V)
4
2
4
6
8
10
INPUT VOLTAGE (V)
12
14
1798 G08
10
100
1k
FREQUENCY (Hz)
10k
1798 G09
1798fc
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LTC1798 Series
TYPICAL PERFORMANCE CHARACTERISTICS
LTC1798-2.5
0.1Hz to 10Hz Noise
1400
V
IN
= 2.7V
1200
INPUT CURRENT (µA)
1000
800
600
400
200
1SEC/DIV
0
1798 G10
LTC1798-5 Input Current
vs Input Voltage in Dropout
250
T
A
= –55°C
T
A
= 25°C
INPUT CURRENT (µA)
T
A
= 125°C
200
150
100
LTC1798-2.5 Input Current
vs Input Voltage in Dropout
T
A
= 125°C
T
A
= 25°C
5µV/DIV
T
A
= –55°C
50
0
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
0
0.5
1
1.5 2 2.5 3 3.5
INPUT VOLTAGE (V)
4
4.5
5
1798 G11
1798 G12
PIN FUNCTIONS
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 0.1µF capaci-
tor 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.
R1
+
R2
V
OUT
=
2.385V
;
R1 is connected from OUT
R2
to FB and R2 from FB to GND. Selecting R2 ≥ 10k will
make I
OUT
< 250µA.
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 0µF to 1µF
.
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