Datasheet

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LTC6655

6655fd

For more information www.linear.com/LTC6655

Typical applicaTion

DescripTion

0.25ppm Noise, Low Drift

Precision References

The LTC

6655 is a complete family of precision bandgap

voltage references, offering exceptional noise and drift

performance. This low noise and drift is ideally suited for

the high resolution measurements required by instrumenta

tion and test equipment. In addition, the LTC6655 is fully

speciﬁed over the temperature range of –40°C to 125°C,

ensuring its suitability for demanding automotive and

industrial applications. Advanced curvature compensation

allows this bandgap reference to achieve a drift of less than

2ppm/°C with a predictable temperature characteristic

and an output voltage accurate to ±0.025%, reducing or

eliminating the need for calibration.

The LTC6655 can be powered from as little as 500mV

above the output voltage to as much as 13.2V. Superior

load regulation with source and sink capability, coupled with

exceptional line rejection, ensures consistent performance

over a wide range of operating conditions. A shutdown

mode is provided for low power applications.

The LTC6655 references are offered in an 8-lead MSOP

package and an 8-lead LS8 package. The LS8 is a 5mm

× 5mm surface mount hermetic package that provides

outstanding stability.

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.

Basic Connection

FeaTures

applicaTions

Low Noise: 0.25ppm

P-P

(0.1Hz to 10Hz)

625nV

P-P

for the LTC6655-2.5

Low Drift: 2ppm/°C Max

High Accuracy: ±0.025% Max

No Humidity Sensitivity (LS8 Package)

Thermal Hysteresis (LS8): 30ppm (–40°C to 85°C)

Long-Term Drift (LS8): 20ppm/√kHr

100% Tested at –40°C, 25°C and 125°C

Load Regulation: <10ppm/mA

Sinks and Sources Current: ±5mA

Low Dropout: 500mV

Maximum Supply Voltage: 13.2V

Low Power Shutdown: <20µA Max

Available Output Voltages: 1.25V, 2.048V, 2.5V, 3V,

3.3V, 4.096V, 5V

Available in an 8-Lead MSOP and High Stability

Hermetic 5mm × 5mm LS8 Packages

Instrumentation and Test Equipment

High Resolution Data Acquisition Systems

Weigh Scales

Precision Battery Monitors

Precision Regulators

Medical Equipment

LTC6655-2.5

SHDN

OUT

10µF

OUT

6655 TA01a

OUT_F

OUT_S

3V < V

≤ 13.2V

GND

0.1µF

Low Frequency 0.1Hz to 10Hz Noise (LTC6655-2.5)

500nV/DIV

6655 TA01b

1s/DIV

Summary of content (26 pages)

PAGE 1
LTC6655 0.25ppm Noise, Low Drift Precision References Features n n n n n n n n n n n n n n Description Low Noise: 0.25ppmP-P (0.1Hz to 10Hz) 625nVP-P for the LTC6655-2.5 Low Drift: 2ppm/°C Max High Accuracy: ±0.025% Max No Humidity Sensitivity (LS8 Package) Thermal Hysteresis (LS8): 30ppm (–40°C to 85°C) Long-Term Drift (LS8): 20ppm/√kHr 100% Tested at –40°C, 25°C and 125°C Load Regulation: <10ppm/mA Sinks and Sources Current: ±5mA Low Dropout: 500mV Maximum Supply Voltage: 13.
PAGE 2
LTC6655 Absolute Maximum Ratings (Note 1) Input Voltage VIN to GND........................................... –0.3V to 13.2V SHDN to GND............................ –0.3V to (VIN + 0.3V) Output Voltage: VOUT_F....................................... –0.3V to (VIN + 0.3V) VOUT_S...................................................... –0.3V to 6V Output Short-Circuit Duration....................... Indefinite Operating Temperature Range (Note 2).. –40°C to 125°C Storage Temperature Range (Note 2)......
PAGE 3
LTC6655 Order Information PART LEAD FREE FINISH TAPE AND REEL MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE LTC6655BHMS8-1.25#PBF LTC6655BHMS8-1.25#TRPBF LTFDG 8-Lead Plastic MSOP –40°C to 125°C LTC6655CHMS8-1.25#PBF LTC6655CHMS8-1.25#TRPBF LTFDG 8-Lead Plastic MSOP –40°C to 125°C LTC6655BHMS8-2.048#PBF LTC6655BHMS8-2.048#TRPBF LTFDH 8-Lead Plastic MSOP –40°C to 125°C LTC6655CHMS8-2.048#PBF LTC6655CHMS8-2.048#TRPBF LTFDH 8-Lead Plastic MSOP –40°C to 125°C LTC6655BHMS8-2.5#PBF LTC6655BHMS8-2.
PAGE 4
LTC6655 AVAILABLE OPTIONS OUTPUT VOLTAGE INITIAL ACCURACY TEMPERATURE COEFFICIENT PART NUMBER† 1.250 0.025% 0.05% 2ppm/°C 5ppm/°C LTC6655BHMS8-1.25 LTC6655CHMS8-1.25 2.048 0.025% 0.05% 2ppm/°C 5ppm/°C LTC6655BHMS8-2.048 LTC6655CHMS8-2.048 2.500 0.025% 0.05% 2ppm/°C 5ppm/°C LTC6655BHMS8-2.5 LTC6655CHMS8-2.5 0.025% 0.05% 2ppm/°C 5ppm/°C LTC6655BHLS8-2.5 LTC6655CHLS8-2.5 3.000 0.025% 0.05% 2ppm/°C 5ppm/°C LTC6655BHMS8-3.0 LTC6655CHMS8-3.0 3.300 0.025% 0.
PAGE 5
LTC6655 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = VOUT + 0.5V, VOUT_S connected to VOUT_F , unless otherwise noted. PARAMETER CONDITIONS Output Short-Circuit Current Short VOUT to GND Short VOUT to VIN Shutdown Pin (SHDN) Logic High Input Voltage Logic High Input Current, SHDN = 2V l l Logic Low Input Voltage Logic Low Input Current, SHDN = 0.
PAGE 6
LTC6655 Typical Performance Characteristics Characteristic curves are similar for most voltage options of the LTC6655. Curves from the LTC6655-1.25, LTC6655-2.5 and the LTC6655-5 represent the range of performance across the entire family of references. Characteristic curves for other output voltages fall between these curves and can be estimated based on their voltage output. 1.25V Low Frequency 0.1Hz to 10Hz Noise 1.25V Output Voltage Temperature Drift 200nV/ DIV 1s/DIV 6655 G01 1.
PAGE 7
LTC6655 Typical Performance Characteristics Characteristic curves are similar for most voltage options of the LTC6655. Curves from the LTC6655-1.25, LTC6655-2.5 and the LTC6655-5 represent the range of performance across the entire family of references. Characteristic curves for other output voltages fall between these curves and can be estimated based on their voltage output. 2.5V Low Frequency 0.1Hz to 10Hz Noise 2.5V Output Voltage Temperature Drift 500nV/ DIV 6655 G10 1s/DIV 2.
PAGE 8
LTC6655 Typical Performance Characteristics Characteristic curves are similar for most voltage options of the LTC6655. Curves from the LTC6655-1.25, LTC6655-2.5 and the LTC6655-5 represent the range of performance across the entire family of references. Characteristic curves for other output voltages fall between these curves and can be estimated based on their voltage output. 2.5V Temperature Drift Distribution 2.5V VOUT Distribution 90 14 TA = 25°C 12 80 NUMBER OF PARTS 70 NUMBER OF PARTS 2.
PAGE 9
LTC6655 Typical Performance Characteristics Characteristic curves are similar for most voltage options of the LTC6655. Curves from the LTC6655-1.25, LTC6655-2.5 and the LTC6655-5 represent the range of performance across the entire family of references. Characteristic curves for other output voltages fall between these curves and can be estimated based on their voltage output. 5V Low Frequency 0.1Hz to 10Hz Noise 5V Output Voltage Temperature Drift 5.
PAGE 10
LTC6655 Pin Functions SHDN (Pin 1): Shutdown Input. This active low input powers down the device to <20µA. If left open, an internal pull-up resistor puts the part in normal operation. It is recommended to tie this pin high externally for best performance during normal operation. VOUT_S (Pin 6): VOUT Sense Pin. Connect this pin at the load and route with a wide metal trace to minimize load regulation errors. This pin sinks 2mA. Output error is RTRACE • 2mA, regardless of load current.
PAGE 11
LTC6655 Applications Information Bypass and Load Capacitors The LTC6655 voltage references require a 0.1µF or larger input capacitor located close to the part to improve power supply rejection. An output capacitor with a value between 2.7µF and 100µF is also required. The output capacitor has a direct effect on the stability, turn-on time and settling behavior. Choose a capacitor with low ESR to insure stability.
PAGE 12
LTC6655 Applications Information The choice of output capacitor also affects the bandwidth of the reference circuitry and resultant noise peaking. As shown in Figure 1, the bandwidth is inversely proportional to the value of the output capacitor. 120 NOISE VOLTAGE (nV√Hz) Noise peaking is related to the phase margin of the output buffer. Higher peaking generally indicates lower phase margin. Other factors affecting noise peaking are temperature, input voltage, and output load current. 80 40 0 0.01 0.
PAGE 13
LTC6655 Applications Information shutdown due to system noise or leakage currents. The turn-on/turn-off response due to shutdown is shown in Figure 8. 0mA IOUT –5mA VOUT 10mV/DIV COUT = 3.3µF 200µs/DIV 6655 F05 Figure 5. Output Response with a 5mA Load Step Sourcing To control shutdown from a low voltage source, a MOSFET can be used as a pull-down device as shown in Figure 9. Note that an external resistor is unnecessary.
PAGE 14
LTC6655 Applications Information 30 4 TYPICAL UNITS LTC6655-2.5 MS8 PACKAGE 80 25 NUMBER OF UNITS LONG-TERM DRIFT (ppm) 120 40 0 –40 20 15 10 5 –80 0 500 1500 1000 HOURS 2000 2500 0 –90 –70 –50 –30 –10 10 30 50 70 90 110 DISTRIBUTION (ppm) 6655 F11 6655 F10 Figure 10a. Long-Term Drift MS8 concern. However, PC board material may absorb water and apply mechanical stress to the LTC6655LS8. Proper board materials and layout are essential. 200 LONG-TERM DRIFT (ppm) LTC6655-2.
PAGE 15
LTC6655 Applications Information 0.14 0.12 5mA LOAD POWER (W) 0.10 LS8 0.08 NO LOAD 0.06 0.04 0.02 6655 F12b 0 Figure 12a. 3-Sided PCB Tab Cutout 0 10 5 15 VIN (V) 6655 F12 Figure 13. LTC6655-2.5 Power Consumption LS8 6655 F12a Figure 12b. 4-Sided PCB Cutout MAXIMUM AMBIENT OPERATING TEMPERATURE (°C) 125 115 NO LOAD 105 5mA LOAD 95 85 75 65 55 0 3 6 9 VIN (V) Power Dissipation Power dissipation for the LTC6655 depends on VIN and load current.
PAGE 16
LTC6655 Applications Information PC Board Layout The LTC6655 reference is a precision device that is factory trimmed to an initial accuracy of ±0.025%, as shown in the Typical Performance Characteristic section. The mechanical stress caused by soldering parts to a printed circuit board may cause the output voltage to shift and the temperature coefficient to change. To reduce the effects of stress-related shifts, mount the reference near the short edge of a printed circuit board or in a corner.
PAGE 17
LTC6655 Applications Information Performance Characteristic section. Noise performance can be further improved by wiring several LTC6655s in parallel as shown in the Typical Applications section. With this technique the noise is reduced by √N, where N is the number of LTC6655s in parallel. Noise Specification Noise in any frequency band is a random function based on physical properties such as thermal noise, shot noise, and flicker noise.
PAGE 18
For more information www.linear.com/LTC6655 15V RST –15V RST LTC6655 2.5V 10k 10k 1µF P P 1µF F S 1µF REFERENCE UNDER TEST SD IN 9V 1300µF 1µF **1.2k T 100k 0.005µF + –15V 4.7k 4.7k A1 LT1012 100k – + 0.005µF A6 1/4 LT1058 – + A5 1/4 LT1058 – SHIELD 100k A = 104 LOW NOISE PRE-AMP 100k + 18 0.1µF – A8 1/4 LT1058 + – A7 1/4 LT1058 –15V Q2 1k – DVM + 1k 5 A2 LT1097 0.
PAGE 19
LTC6655 Applications Information of expansion and contraction. After a part undergoes the extreme heat of a lead-free IR reflow profile, like the one shown in Figure 20, the output voltage shifts. After the device expands, due to the heat, and then contracts, the stresses on the die have changed position. This shift is similar, but more extreme than thermal hysteresis. 35 NUMBER OF OBSERVATIONS 30 25 20 15 Experimental results of IR reflow shift are shown below in Figure 21.
PAGE 20
LTC6655 Typical Applications Extended Supply Range Reference Extended Supply Range Reference 4V TO 30V R1 BZX84C12 C1 0.1µF 6V TO 80V R1 R2 100k 4.7k LTC6655-2.5 VIN VOUT_F SHDN VOUT_S VOUT BZX84C12 C2 10µF GND ON SEMI MMBT5551 C1 0.1µF 0.1µF VIN SHDN VOUT_F LTC6655-2.5 VOUT_S GND 6655 TA02 VOUT C2 10µF 6655 TA03 Boosted Output Current Boosted Output Current 4V TO 13.2V VOUT + 1.8V TO 13.2V LTC6655-2.5 SHDN VOUT_F VIN C1 0.1µF 6655 TA05 GND Q1 2N2222 VOUT VOUT_S C3 0.1µF C2 4.
PAGE 21
LTC6655 Typical Applications Output Voltage Boost VIN VOUT + 0.5V TO 13.2V VIN C1 1µF VOUT_F LTC6655-2.5 SHDN VOUT_S GND VOUT = VOLTAGE OPTION + 0.002 • R THIS EXAMPLE USES 2.5V AS THE VOLTAGE OPTION C2 10µF R VOUT 2.5V TO 4.5V R = 0k to 1k 6655 TA07 FOR R USE A POTENTIOMETER THAT CAN HANDLE 2mA, IS LOW NOISE AND HAS A LOW TEMPERATURE COEFFICIENT Low Noise Precision Voltage Boost Circuit VIN VOUT + 0.5V TO 13.2V C1 1µF VIN VOUT_F LTC6655-2.
PAGE 22
LTC6655 Typical Applications Low Noise Statistical Averaging Reference e′N = eN/√N; Where N is the Number of LTC6655s in Parallel LTC6655-2.5 SHDN VOUT_F 3V TO 13.2V VIN C1 0.1µF GND R1 32.4Ω VOUT_S VOUT C2 2.7µF C9 4.7µF LTC6655-2.5 SHDN VOUT_F VIN C3 0.1µF GND R2 32.4Ω VOUT_S C4 2.7µF LTC6655-2.5 SHDN VOUT_F VIN C5 0.1µF GND R3 32.4Ω VOUT_S C6 2.7µF LTC6655-2.5 SHDN VOUT_F VIN 6655 TA06a C7 0.1µF GND VOUT_S R4 32.4Ω C8 2.7µF Low Frequency Noise (0.
PAGE 23
LTC6655 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660 Rev G) 0.889 ±0.127 (.035 ±.005) 5.10 (.201) MIN 3.20 – 3.45 (.126 – .136) 3.00 ±0.102 (.118 ±.004) (NOTE 3) 0.65 (.0256) BSC 0.42 ± 0.038 (.0165 ±.0015) TYP 8 7 6 5 0.52 (.0205) REF RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 3.00 ±0.102 (.118 ±.004) (NOTE 4) 4.90 ±0.152 (.193 ±.
PAGE 24
LTC6655 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. LS8 Package 8-Pin Leadless Chip Carrier (5mm × 5mm) (Reference LTC DWG # 05-08-1852 Rev B) 8 2.50 ±0.15 PACKAGE OUTLINE 7 1 0.5 2 6 2.54 ±0.15 1.4 3 1.50 ±0.15 4 0.70 ±0.05 × 8 e4 XYY ZZ ABCDEF Q12345 COMPONENT PIN “A1” 5.00 SQ ±0.15 5.80 SQ ±0.15 TRAY PIN 1 BEVEL APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 5.00 SQ ±0.15 1.45 ±0.10 0.95 ±0.10 4.20 SQ ±0.
PAGE 25
LTC6655 Revision History REV DATE DESCRIPTION A 02/10 Voltage Options Added (1.250, 2.048, 3.000, 3.300, 4.096, 5.
PAGE 26
LTC6655 Typical Application Low Noise Precision 24-Bit Analog-to-Digital Converter Application 2.5k 5V VREF THERMOCOUPLE 0.01µF LTC2449 0.01µF 1nF 50Ω SDI SCK SDO CS SPI INTERFACE – 1/2 LTC6241 + BUSY EXT fO GND 10µF 2.5k ADCINP REF+ REF– 4 – 1/2 LTC6241 –2.5V MUXOUTP GND GND 50Ω + GND GND 3,5,8 MUXOUTN ADCINN GND 0.1µF VREF GND LTC6655 7 VOUT_F 1 6 SHDN VOUT_S VIN 1nF GND RTD 2 VCC CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 CH9 CH10 CH11 CH12 CH13 CH14 CH15 COM GND 5k 7.