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 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 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.
■
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
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
Micropower Low
Dropout References
■
Battery-Powered Systems
■
Handheld Instruments
■
Precision Power Supplies
■
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
62.5V
1798 TA01
0.1µF
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
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
(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
TJMAX = 125°C, θJA = 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
U
The ● denotes specifications which apply over the full specified temperature range, otherwise specifications are at TA = 25°C.
VIN = VOUT(NOMINAL) + 0.2V, IOUT = 0mA unless otherwise noted. FB = OUT for the LTC1798.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Input Voltage Range ●12.6 V
I
IN
Input Current FB = OUT for LTC1798 4.0 6.5 µA
●8.5 µA
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 ● denotes specifications which apply over the full specified temperature range, otherwise specifications are at TA = 25°C.
VIN = VOUT(NOMINAL) + 0.2V, IOUT = 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
●15 40 ppm/°C
V
OUT
/V
IN
Line Regulation V
IN
= (V
OUT(NOMINAL)
+ 0.2V) to 12.6V ●30 120 ppm/V
V
OUT
/I
OUT
Load Regulation (Note 7) Sourcing 0mA to 10mA ●0.1 0.3 mV/mA
Sinking 0mA to 2mA 1.75 4.0 mV/mA
●6.5 mV/mA
I
SC
Short-Circuit Output Current V
OUT
Shorted to GND 20 40 mA
V
OUT
Shorted to V
IN
24 mA
∆V
DO
Dropout Voltage (Note 8) I
OUT
= 0, ∆V
OUT
≤ 0.1% ●100 mV
I
OUT
= 10mA, ∆V
OUT
≤ 0.1% ●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
UW
OUTPUT SOURCE CURRENT (mA)
DROPOUT VOLTAGE (mV)
100
90
80
70
60
50
40
30
20
10
00 1 10 100
1798 G01
0.1
T
A
= 25°C
TEMPERATURE (°C)
–50 –25
INPUT CURRENT (µA)
150
1798 G02
025
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
025
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
UW
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
046810
1258-G04
12 14
T
A
= 25°C
OUTPUT SHORTED
TO V
IN
INPUT VOLTAGE (V)
2
OUTPUT SHORT-CIRCUIT CURRENT (mA)
42
41 46810
1798 G05
12 14
TA = 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 46810
1798 G07
12 14
T
A
= 25°C
INPUT VOLTAGE (V)
2
INPUT CURRENT (µA)
7
6
5
446810
1798 G08
12 14
TA = 25°C
FREQUENCY (Hz)
POWER SUPPLY REJECTION RATIO (dB)
60
50
40
30
20
10
010 1k 10k
1798 G09
100
V
IN
= 2.7V
5µV/DIV
1798 G10
1SEC/DIV
V
IN
= 2.7V
INPUT VOLTAGE (V)
012345678910
INPUT CURRENT (µA)
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)
00.5 1 1.5 2 2.5 3 3.5 4 4.5 5
INPUT CURRENT (µA)
1798 G12
250
200
150
100
50
0
TA = 25°C
TA = –55°C
TA = 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 0.1µF
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.
VV
RR
R
OUT
=+
2 385 12
2
.;
R1 is connected from OUT
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.
–
+
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
W
PI FU CTIO S
UUU
LTC1798 Series
6
Longer Battery Life
Series references have an advantage over shunt style
references. To operate, shunt references require a resistor
between the power supply and the output. This resistor
must be chosen to supply the maximum current that is
demanded by the circuit being regulated. When the circuit
being controlled is not operating at this maximum current,
the shunt reference must always sink this current, result-
ing in high power dissipation and short battery life.
The LTC1798 series low dropout references do not require
a current setting resistor and can operate with any supply
voltage from (V
OUT(NOMINAL)
+ 0.2V) to 12.6V. When the
circuitry being regulated does not demand current, the
LTC1798 series reduces its dissipation and battery life is
extended. If the reference is not delivering load current it
dissipates only 10.8µW when operating on a 2.7V supply
for LTC1798-2.5, yet the same connection can deliver
10mA of load current when demanded.
Output Bypass Capacitor
The LTC1798 series is designed to be stable with or
without capacitive loads. With no capacitive load, the
reference is ideal for fast settling applications, or where PC
board space is at a premium.
In applications with significant output loading changes,
an output bypass capacitor of up to 1µF can be used to
improve the output transient response. Figure 1 shows
the response of the reference to a 1mA to 0µA load step
with a 1µF output capacitor. If more than 1µF of output
capacitance is required, a resistor in series with the
capacitor is recommended to reduce the output ringing.
Figure 2 illustrates the use of a damping resistor for
capacitive loads greater than 1µF. Figure 3 shows the
resistor and capacitor values required to achieve critical
damping.
Figure 1. Reference Output Load Transient Response, 1µF Output Capacitor
Figure 2. Adding a Damping Resistor with
Output Capacitors Greater Than 1µF
Figure 3. Damping Resistance vs Output Capacitor Value
1mA
0mA
I
OUT
V
OUT
100mV/DIV
10ms/DIV
1798 F01a
1mA
0mA
I
OUT
V
OUT
100mV/DIV
0.5ms/DIV
1798 F01b
LTC1798-5
OUT
IN
GND
4
2
5.2V
TO
12.6V
65V
1798 F02
0.1µF
C
OUT
>1µF
DAMPING RESISTOR
<1k
OUTPUT CAPACITOR VALUE (µF)
1
10
RESISTOR VALUE (Ω)
100
1k
10k
10 100 1000
1798 F03
APPLICATIO S I FOR ATIO
WUUU
LTC1798 Series
7
Internal P-Channel Pass Transistor
The LTC1798 series features an internal P-channel MOSFET
pass transistor. This provides several advantages over
similar designs using a PNP bipolar pass transistor.
These references consume only 4µA of quiescent current
under light and heavy loads as well as in dropout; whereas,
PNP-based references waste considerable amounts of
current when the pass transistor is saturated. In addition,
the LTC1798 series provides a lower dropout voltage
(200mV max) than PNP-based references.
APPLICATIO S I FOR ATIO
WUUU
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) unless otherwise noted.
0.016 – 0.050
(0.406 – 1.270)
0.010 – 0.020
(0.254 – 0.508)× 45°
0°– 8° TYP
0.008 – 0.010
(0.203 – 0.254)
SO8 1298
0.053 – 0.069
(1.346 – 1.752)
0.014 – 0.019
(0.355 – 0.483)
TYP
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
1234
0.150 – 0.157**
(3.810 – 3.988)
8765
0.189 – 0.197*
(4.801 – 5.004)
0.228 – 0.244
(5.791 – 6.197)
DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
LTC1798 Series
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 1999
1798fa LT/LCG 1100 2K REV A • PRINTED IN USA
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LT1460 Micropower Series Reference 0.075% Max, 10ppm/°C Max Drift, 2.5V, 5V and 10V Outputs
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MICROWIRE is a trademark of National Semiconductor Corporation.
+
–
1
4
8
V
SS
= –4V
V
OUT
= –3V
0.2V ≤ V
CC
≤ 8.5V
3
2
LTC1798-3
1/2 LTC1542
OUT
GND
4
6
1798 TA03
IN
2
0.1µF
LTC1798-2.5
OUT
IN
GND
4
2
V
CC
= 5V 62.5V
VIRTUAL
GROUND
1798 TA04
0.1µF0.1µF
LTC1798-3
LTC1096L
MPU
SERIAL DATA LINK
(MICROWIRE
TM
AND
SPI COMPATIBLE)
OUT
IN
GND
CS/
SHDN
+IN
–IN
GND
V
CC
CLK
D
OUT
V
REF
ANALOG INPUT
0V TO 3V RANGE
1
2
3
4
8
7
6
5
42V
IN
3.2V TO
12.6V
6
1798 TA05
1µF
SERIAL DATA LINK
0.1µF
Micropower Low Dropout Negative Reference Supply Splitter
Low Power, Low Voltage Supply Reference for LTC1096L
TYPICAL APPLICATIO S
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