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LTC1798
Technical data
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LINEAR TECHNOLOGY LTC1798 Technical data

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FEATURES
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
Micropower Low
Dropout References
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DESCRIPTIO
■
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
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APPLICATIO S
■
Battery-Powered Systems
■
Handheld Instruments
■
Precision Power Supplies
■
A/D and D/A Converters
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.
TYPICAL APPLICATIO
2.5V Battery-Powered Reference
2.7V
TO 12.6V
0.1µF
2
IN
LTC1798-2.5
GND
4
OUT
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The LTC1798 series is available in the SO-8 package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
LTC1798-2.5 Temperature Drift
6
2.5V
1798 TA01
1
LTC1798 Series
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
WW
W
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ABSOLUTE AXI U RATI GS
(Note 1)
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
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AVAILABLE OPTIO S
UUW
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
LTC1798CS8 LTC1798CS8-2.5 LTC1798CS8-3 LTC1798CS8-4.1 LTC1798CS8-5
T
= 125°C, θJA = 190°C/W
JMAX
* 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
Consult factory for parts specified with wider operating temperature range.
S8 PART MARKING
1798 179825 17983 179841 17985
OUTPUT TEMPERATURE TEMPERATURE
VOLTAGE RANGE ACCURACY COEFFICIENT
(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
PACKAGE TYPE
SO-8 (S8)
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full specified temperature range, otherwise specifications are at TA = 25°C. VIN = V
OUT(NOMINAL)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
I
IN
V
OUT
2
+ 0.2V, I
Input Voltage Range ● 12.6 V Input Current FB = OUT for LTC1798 4.0 6.5 µA
Output Voltage (Note 4) LTC1798, FB = OUT 2.3755 2.385 2.3945 V
= 0mA unless otherwise noted. FB = OUT for the LTC1798.
OUT
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 %
● 8.5 µA
LTC1798 Series
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full specified temperature range, otherwise specifications are at TA = 25°C. VIN = V
OUT(NOMINAL)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
e
n
TC Output Voltage Temp Coefficient (Note 6) T V
OUT/VIN
V
OUT/IOUT
I
SC
∆V
DO
V
HYST
I
FB
+ 0.2V, I
Output Voltage Noise (Note 5) 0.1Hz ≤ f ≤ 10Hz 8 ppm
Line Regulation VIN = (V
= 0mA unless otherwise noted. FB = OUT for the LTC1798.
OUT
≤ TJ ≤ T
MIN
MAX
OUT(NOMINAL)
+ 0.2V) to 12.6V ● 30 120 ppm/V
P-P
● 15 40 ppm/°C
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
Short-Circuit Output Current V
Dropout Voltage (Note 8) I
Shorted to GND 20 40 mA
OUT
Shorted to V
V
OUT
= 0, ∆V
OUT
= 10mA, ∆V
I
OUT
IN
≤ 0.1% ● 100 mV
OUT
≤ 0.1% ● 200 mV
OUT
24 mA
Output Hysteresis (Note 9) ∆T = –40°C to 85°C 200 ppm
∆T = 0°C to 70°C 50 ppm
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 nominal value at V
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.
UW
TYPICAL PERFOR A CE CHARACTERISTICS
LTC1798-2.5* Dropout Voltage vs Output Source Current
100
TA = 25°C
90 80 70 60 50 40 30
DROPOUT VOLTAGE (mV)
20 10
0
0 1 10 100
*Similar performance characteristics can be expected for all voltage options.
0.1
OUTPUT SOURCE CURRENT (mA)
1798 G01
LTC1798-2.5* Input Current vs Temperature
8
VIN = 2.7V
7
6
5
4
3
INPUT CURRENT (µA)
2
1
0
–50 –25
025
50 75
TEMPERATURE (°C)
100 125
1798 G02
IN
150
– V
) when V
OUT
= V
OUT
IN
+ 0.5V.
LTC1798 Series Output Short­Circuit Current vs Temperature
70
TA = 25°C V
= V
60
IN
OUT(NOM)
50
40
30
20
10
5
OUTPUT SHORT-CIRCUIT CURRENT (mA)
0
–50 –25
025
falls to 0.1% below its
OUT
+ 0.2V
50 75
TEMPERATURE (°C)
OUTPUT SHORTED TO GND
OUTPUT SHORTED TO V
100 125
IN
1798 G03
150
3
LTC1798 Series
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
TA = 25°C V
IN
= V
OUT(NOM)
+ 0.2V
SINKING
SOURCING
UW
TYPICAL PERFOR A CE CHARACTERISTICS
LTC1798-2.5* Output Short-Circuit Current vs Input Voltage
25
TA = 25°C OUTPUT SHORTED TO V
20
15
10
OUTPUT SHORT-CIRCUIT CURRENT (mA)
IN
5
0
2
6810
4
INPUT VOLTAGE (V)
LTC1798-2.5* Output Voltage vs Input Voltage
2.5010
2.5005
TA = 25°C
12 14
1258-G04
LTC1798-2.5* Output Short-Circuit Current vs Input Voltage
42
TA = 25°C OUTPUT SHORTED TO GND
OUTPUT SHORT-CIRCUIT CURRENT (mA)
41
2
6810
4
INPUT VOLTAGE (V)
LTC1798-2.5* Input Current vs Input Voltage
7
TA = 25°C
6
LTC1798 Series Load Regulation
12 14
1798 G05
LTC1798-2.5 PSRR vs Frequency
60
VIN = 2.7V
50
40
2.5000
OUTPUT VOLTAGE (V)
2.4995 2
6810
4
INPUT VOLTAGE (V)
LTC1798-2.5 0.1Hz to 10Hz Noise
VIN = 2.7V
5µV/DIV
4
1SEC/DIV
12 14
1798 G07
1798 G10
5
INPUT CURRENT (µA)
4
2
6810
4
INPUT VOLTAGE (V)
LTC1798-5 Input Current vs Input Voltage in Dropout
1400
TA = –55°C
TA = 25°C
TA = 125°C
0
012345678910
INPUT VOLTAGE (V)
INPUT CURRENT (µA)
1200
1000
800
600
400
200
12 14
1798 G08
1798 G11
30
20
10
POWER SUPPLY REJECTION RATIO (dB)
0
10 1k 10k
100
FREQUENCY (Hz)
LTC1798-2.5 Input Current vs Input Voltage in Dropout
250
200
TA = 125°C
150
100
INPUT CURRENT (µA)
50
0
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
INPUT VOLTAGE (V)
TA = 25°C
TA = –55°C
1798 G09
1798 G12
VV
RR
R
OUT
=
+
 
 
2 385
12
2
.;
UUU
PI FU CTIO S
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
+ 0.2V) ≤ VIN ≤ 12.6V.
OUT
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.
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BLOCK DIAGRA
LTC1798 Series
R1 is connected from OUT
to FB and R2 from FB to GND. Selecting R2 ≥ 10k will make I
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.
< 250µA.
OUT
2 IN
+
2.385V
GND
4
NOTE: R1 AND R2 ARE NOT CONNECTED FOR LTC1798
–
OUT
R1
R2
1798 BD
6
3 (LTC1798)FB
5
LTC1798 Series
OUTPUT CAPACITOR VALUE (µF)
1
10
RESISTOR VALUE (Ω)
100
1k
10k
10 100 1000
1798 F03
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WUU
APPLICATIO S I FOR ATIO
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, result­ing 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)
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.
+ 0.2V) to 12.6V. When the
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.
5.2V TO
12.6V
0.1µF
Figure 2. Adding a Damping Resistor with Output Capacitors Greater Than 1µF
LTC1798-5
2
IN
GND
4
OUT
6
C
OUT
>1µF
DAMPING RESISTOR <1k
5V
1798 F02
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
1mA
I
OUT
0mA
V
OUT
100mV/DIV
Figure 3. Damping Resistance vs Output Capacitor Value
1mA
I
OUT
0mA
V
OUT
100mV/DIV
10ms/DIV
6
Figure 1. Reference Output Load Transient Response, 1µF Output Capacitor
1798 F01a
0.5ms/DIV
1798 F01b
LTC1798 Series
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WUU
APPLICATIO S I FOR ATIO
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.
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PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
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.
0.189 – 0.197* (4.801 – 5.004)
7
8
5
6
0.228 – 0.244
(5.791 – 6.197)
0.010 – 0.020
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
*
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
×
°
45
0.016 – 0.050
(0.406 – 1.270)
0°– 8° TYP
0.053 – 0.069
(1.346 – 1.752)
0.014 – 0.019
(0.355 – 0.483)
TYP
0.150 – 0.157** (3.810 – 3.988)
1
3
2
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
SO8 1298
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 represen­tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
7
LTC1798 Series
TYPICAL APPLICATIO S
Micropower Low Dropout Negative Reference Supply Splitter
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2
–
1/2 LTC1542
3
+
= –4V
V
SS
OUT
CC
= –3V
≤ 8.5V
LTC1798-2.5
0.1µF
2
IN
GND
4
V
= 5V
CC
OUT
6
0.1µF
1798 TA04
2.5V VIRTUAL GROUND
2
IN
6
LTC1798-3
OUT
8
4
0.1µF
1
GND
4
0.2V ≤ V
V
1798 TA03
Low Power, Low Voltage Supply Reference for LTC1096L
ANALOG INPUT
0V TO 3V RANGE
1
CS/ SHDN
2
+IN
LTC1096L
3
–IN
4
GND
4
D
V
V
CLK
OUT
REF
CC
GND
8 7 6 5
OUT
LTC1798-3
1µF
SERIAL DATA LINK
6
2
IN
0.1µF
MPU
SERIAL DATA LINK
(MICROWIRE
SPI COMPATIBLE)
V
IN
3.2V TO
12.6V
TM
AND
1798 TA05
MICROWIRE is a trademark of National Semiconductor Corporation.
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT®1389 Nanopower Precision Shunt Voltage Reference 800nA Quiescent Current, 0.05% Max, 10ppm/°C Max Drift
1.25V and 2.5V Versions, SO-8 Package
LT1634 Micropower Precision Shunt Voltage Reference 0.05% Max, 25ppm/°C Max Drift, 1.25V, 2.5V, 4.096V and 5V Outputs LT1460 Micropower Series Reference 0.075% Max, 10ppm/°C Max Drift, 2.5V, 5V and 10V Outputs LT1461 Micropower Precision Series Voltage Reference 0.04% Max, 3ppm/°C Max Drift, 35µA Quiescent Current LT1790 SOT-23, LDO Precision Micropower Reference 0.05% Max, 10ppm/°C Max, 2.5V, 60µA Supply
1798fa LT/LCG 1100 2K REV A • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1999
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear-tech.com
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