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LTC6652 Precision Low Drift Low Noise Buffered Reference FEATURES
n n n n n n n n n n n n
DESCRIPTION
The LTC(R)6652 family of precision, low drift, low noise references is fully specified over the temperature range of -40C to 125C. High order curvature compensation allows these references to achieve a low drift of less than 5ppm/C with a predictable temperature characteristic and an output voltage accuracy of 0.05%. The performance over temperature should appeal to automotive, highperformance industrial and other high temperature applications. The LTC6652 voltage references can be powered from a 13.2V supply or as little as 300mV above the output voltage or 2.7V; whichever is higher. The LTC6652 references are offered in an 8-Lead MSOP package. They boast low noise, excellent load regulation, source and sink capability and exceptional line rejection, making them a superior choice for demanding precision applications. A shutdown mode allows power consumption to be reduced when the reference is not needed. The optional output capacitor can be left off when space constraints are critical.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Low Drift: A Grade 5ppm/C Max B Grade 10ppm/C Max High Accuracy: A Grade 0.05%, B Grade 0.1% Low Noise: 2.1ppmp-p (0.1Hz to 10Hz) 100% Tested at -40C, 25C and 125C Sinks and Sources Current: 5mA Low Power Shutdown: <2A Maximum Thermal Hysteresis: 105ppm for -40C to 125C Range Low Dropout: 300mV No External Load Capacitor Required Wide Supply Range to 13.2V Available Output Voltage Options: 1.25V, 2.048V, 2.5V, 3V, 3.3V, 4.096V, 5V 8-Lead MSOP Package
APPLICATIONS
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Automotive Control and Monitoring High Temperature Industrial High Resolution Data Acquisition Systems Instrumentation and Process Control Precision Regulators Medical Equipment
TYPICAL APPLICATION
0.050
Output Voltage Temperature Drift
Basic Connection
VOUT ACCURACY (%) 0.025
2.8V
VIN
13.2V
VIN SHDN
LTC6652-2.5 VOUT GND
VOUT 2.5V COUT 1F (OPTIONAL)
6652 TA01a
CIN 0.1 F (OPTIONAL)
0
-0.025
-0.050 -40 -20
0
20 40 60 80 TEMPERATURE (C)
100
125
6652 TA01b
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LTC6652 ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW DNC VIN SHDN GND 1 2 3 4 8 7 6 5 GND* GND* VOUT GND*
Input Voltage VIN to GND .......................................... -0.3V to 13.2V SHDN to GND ............................-0.3V to (VIN + 0.3V) Output Voltage VOUT...........................................-0.3V to (VIN + 0.3V) Output Short-Circuit Duration ...................... Indefinite Operating Temperature Range ................ -40C to 125C Storage Temperature Range (Note 2) ..... -65C to 150C Lead Temperature Range (Soldering, 10 sec) (Note 9)............................................................. 300C
MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150C, JA = 200C/W DNC: DO NOT CONNECT *CONNECT THE PINS TO DEVICE GND (PIN 4)
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC6652AHMS8-1.25#PBF LTC6652AHMS8-1.25#TRPBF LTCVH 8-Lead Plastic MSOP -40C to 125C LTC6652BHMS8-1.25#PBF LTC6652BHMS8-1.25#TRPBF LTCVH 8-Lead Plastic MSOP -40C to 125C LTC6652AHMS8-2.048#PBF LTC6652AHMS8-2.048#TRPBF LTCVJ 8-Lead Plastic MSOP -40C to 125C LTC6652BHMS8-2.048#PBF LTC6652BHMS8-2.048#TRPBF LTCVJ 8-Lead Plastic MSOP -40C to 125C LTC6652AHMS8-2.5#PBF LTC6652AHMS8-2.5#TRPBF LTCQV 8-Lead Plastic MSOP -40C to 125C LTC6652BHMS8-2.5#PBF LTC6652BHMS8-2.5#TRPBF LTCQV 8-Lead Plastic MSOP -40C to 125C LTC6652AHMS8-3#PBF LTC6652AHMS8-3#TRPBF LTCVK 8-Lead Plastic MSOP -40C to 125C LTC6652BHMS8-3#PBF LTC6652BHMS8-3#TRPBF LTCVK 8-Lead Plastic MSOP -40C to 125C LTC6652AHMS8-3.3#PBF LTC6652AHMS8-3.3#TRPBF LTCVM 8-Lead Plastic MSOP -40C to 125C LTC6652BHMS8-3.3#PBF LTC6652BHMS8-3.3#TRPBF LTCVM 8-Lead Plastic MSOP -40C to 125C LTC6652AHMS8-4.096#PBF LTC6652AHMS8-4.096#TRPBF LTCVN 8-Lead Plastic MSOP -40C to 125C LTC6652BHMS8-4.096#PBF LTC6652BHMS8-4.096#TRPBF LTCVN 8-Lead Plastic MSOP -40C to 125C LTC6652AHMS8-5#PBF LTC6652AHMS8-5#TRPBF LTCVP 8-Lead Plastic MSOP -40C to 125C LTC6652BHMS8-5#PBF LTC6652BHMS8-5#TRPBF LTCVP 8-Lead Plastic MSOP -40C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. 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
INITIAL ACCURACY TEMPERATURE COEFFICIENT 0.05% 5ppm/C 0.1% 10ppm/C 2.048 0.05% 5ppm/C 0.1% 10ppm/C 2.500 0.05% 5ppm/C 0.1% 10ppm/C 3.000 0.05% 5ppm/C 0.1% 10ppm/C 3.300 0.05% 5ppm/C 0.1% 10ppm/C 4.096 0.05% 5ppm/C 0.1% 10ppm/C 5.000 0.05% 5ppm/C 0.1% 10ppm/C **See Order Information section for complete part number listing. OUTPUT VOLTAGE 1.250 PART NUMBER** LTC6652AHMS8-1.25 LTC6652BHMS8-1.25 LTC6652AHMS8-2.048 LTC6652BHMS8-2.048 LTC6652AHMS8-2.5 LTC6652BHMS8-2.5 LTC6652AHMS8-3 LTC6652BHMS8-3 LTC6652AHMS8-3.3 LTC6652BHMS8-3.3 LTC6652AHMS8-4.096 LTC6652BHMS8-4.096 LTC6652AHMS8-5 LTC6652BHMS8-5
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LTC6652 ELECTRICAL CHARACTERISTICS
PARAMETER Output Voltage Output Voltage Temperature Coefficient (Note 3) Line Regulation Load Regulation (Note 4)
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C, VIN = VOUT + 0.5V, unless otherwise noted.
CONDITIONS LTC6652A LTC6652B LTC6652A LTC6652B VOUT + 0.5V VIN 13.2V, SHDN = VIN ISOURCE = 5mA, LTC6652-1.25, LTC6652-2.048, LTC6652-2.5, LTC6652-3, LTC6652-3.3, LTC66524.096, LTC6652-5 ISINK = 1mA, LTC6652-1.25, LTC6652-2.048 ISINK = 5mA, LTC6652-2.5, LTC6652-3, LTC6652-3.3, LTC6652-4.096, LTC6652-5 ISOURCE = 5mA, VOUT Error 0.1% LTC6652-1.25, LTC6652-2.048 LTC6652-2.5, LTC6652-3, LTC6652-3.3, LTC6652-4.096, LTC6652-5 Short VOUT to GND Short VOUT to VIN Logic High Input Voltage Logic High Input Current Logic Low Input Voltage Logic Low Input Current No Load SHDN Tied to GND 0.1Hz f 10Hz LTC6652-1.25 LTC6652-2.048, LTC6652-2.5, LTC6652-3 LTC6652-3.3 LTC6652-4.096 LTC6652-5 10Hz f 1kHz 0.1% Settling, CLOAD = 0 MIN -0.05 -0.1
l l l l
TYP
2 4 2 20
MAX 0.05 0.1 5 10 50 80 75 200 250 600 150 450
UNITS % % ppm/C ppm/C ppm/V ppm/V ppm/mA ppm/mA ppm/mA ppm/mA ppm/mA ppm/mA V V
l l l l
80 50
Minimum Operating Voltage (Note 5)
2.7 VOUT + 0.3V 16 16
Output Short-Circuit Current Shutdown Pin (SHDN)
l l l l l l
2 0.1 0.1 350 0.1 2.4 2.1 2.2 2.3 2.8 3 100 60 105 1 0.8 1 560 2
Supply Current Shutdown Current Output Voltage Noise (Note 6)
mA mA V A V A A A A ppmP-P ppmP-P ppmP-P ppmP-P ppmP-P ppmRMS s ppm/khr ppm
Turn-On Time Long Term Drift of Output Voltage (Note 7) Hysteresis (Note 8) T = -40C to 125C
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: If the parts are stored outside of the specified temperature range, the output may shift due to hysteresis. Note 3: Temperature coefficient is measured by dividing the maximum change in output voltage by the specified temperature range. Note 4: 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 5: Excludes load regulation errors. Note 6: Peak-to-peak noise is measured with a 3-pole highpass at 0.1Hz and 4-pole lowpass filter at 10Hz. The unit is enclosed in a still-air environment to eliminate thermocouple effects on the leads. The test time is 10 seconds. RMS noise is measured on a spectrum analyzer in a shielded environment where the intrinsic noise of the instrument is
removed to determine the actual noise of the device. Note 7: Long term stability typically has a logarithmic characteristic and therefore, changes after 1000 hours tend to be much smaller than before that time. Total drift in the second thousand hours is normally less than one third that of the first thousand hours with a continuing trend toward reduced drift with time. Long-term stability will also be affected by differential stresses between the IC and the board material created during board assembly. Note 8: 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 25C, but the IC is cycled to the hot or cold temperature limit before successive measurements. Hysteresis is roughly proportional to the square of the temperature change. For instruments that are stored at well controlled temperatures (within 20 or 30 degrees of operational temperature) it's usually not a dominant error source. Note 9: The stated temperature is typical for soldering of the leads during manual rework. For detailed IR reflow recommendations, refer to the Applications section.
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LTC6652
Characteristic curves are similar for most LTC6652s. Curves from the LTC6652-1.25, LTC6652-2.5 and the LTC6652-5 represent the extremes and typical of the voltage options. Characteristic curves for other output voltages fall between these curves and can be estimated based on their output. 1.25V Output Voltage Temperature Drift
1.2510 3 TYPICAL PARTS 1.2506 1.2504 REFERENCE VOLTAGE (V) OUTPUT VOLTAGE (V) 1.2505 125C 1.2502 1.2500 25C 1.2498 1.2496 1.2490 -80 1.2494 0 2 8 6 10 4 INPUT VOLTAGE (V) 12 14
6652 G18
TYPICAL PERFORMANCE CHARACTERISTICS
1.25V Line Regulation
1.25V Load Regulation (Sourcing)
0 OUTPUT VOLTAGE CHANGE (ppm) -40 C -50 25 C 125 C -150
-100
1.2500
1.2495
-40C
-200
-40
80 40 0 TEMPERATURE (C)
120
160
6652 G17
-250 0.1
1 OUTPUT CURRENT (mA)
10
6652 G19
1.25V Load Regulation (Sinking)
400 OUTPUT VOLTAGE CHANGE (ppm) 350 125C OUTPUT NOISE (1V/DIV) 300 250 200 150 100 -40C 50 0 0.1 1 OUTPUT CURRENT (mA) 10
6652 G20
1.25V Low Frequency 0.1Hz to 10Hz Transient Noise
400
1.25V Output Voltage Noise Spectrum
NOISE VOLTAGE (nV/Hz) TIME (1 SECOND/DIV)
6652 G21
300
25C
200
100
0 0.01
0.1 1 FREQUENCY (kHz)
10
6652 G22
1.25 Sinking Current Without Output Capacitor
1mA IOUT 0mA IOUT 1mA 0mA
1.25 Sinking Current with Output Capacitor
10F 1F OUTPUT CAPACITOR 0.1F 10nF 1nF 100pF NO CAP
1.25V Stability with Output Capacitance
VOUT 500mV/DIV
VOUT 500mV/DIV
REGION OF MARGINAL STABILITY
500s/DIV COUT = 0F
6652 G23
500s/DIV COUT = 1F
6652 G24
-5
-1 0 LOAD CURRENT (mA)
5
6652 G16
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LTC6652
Characteristic curves are similar for most LTC6652s. Curves from the LTC6652-1.25, LTC6652-2.5 and the LTC6652-5 represent the extremes and typical of the voltage options. Characteristic curves for other output voltages fall between these curves and can be estimated based on their output. 2.5V Output Voltage Temperature Drift
2.5010 3 TYPICAL PARTS 2.5010 2.5005 OUTPUT VOLTAGE (V) 2.5000 2.4995 2.4990 2.4985 2.4980 0 2 8 6 10 4 INPUT VOLTAGE (V) 12 14
6652 G02
TYPICAL PERFORMANCE CHARACTERISTICS
2.5V Line Regulation
2.5V Load Regulation (Sourcing)
0 -20 OUTPUT VOLTAGE CHANGE (ppm) -40C
REFERENCE VOLTAGE (V)
2.5005
-40 -60 -80 -100 -120 -140 -160 -180 25C 125C
125C 25C -40C
2.5000
2.4995
2.4990
2.4985 -50 -25
-200 0.1
0
25 50 75 100 125 150 TEMPERATURE (C)
6652 G01
1 OUTPUT CURRENT (mA)
10
6652 G03
2.5V Load Regulation (Sinking)
700 OUTPUT VOLTAGE CHANGE (ppm) 600 SUPPLY CURRENT (A) 500 400 125C 200 100 0 0.1 1 OUTPUT CURRENT (mA) 10
6652 G04
2.5V Supply Current vs Input Voltage
1000 900 800 700 600 500 400 300 200 125C 25C -40C SUPPLY CURRENT (A) 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 2 8 6 4 10 INPUT VOLTAGE (V) 12 14 0
2.5V Shutdown Current vs Input Voltage
125C
25C -40C
25C -40C 0 2 8 6 4 10 INPUT VOLTAGE (V) 12 14
100 0
6652 G05
6652 G06
2.5V Minimum VIN-VOUT Differential (Sourcing)
10 10
2.5V Minimum VOUT-VIN Differential (Sinking)
OUTPUT CURRENT (mA)
1
OUTPUT CURRENT (mA)
1
0.1
25C 125C, -40C
25C 125C -40C
0.01 0.001
0.01
0.1
1
6652 G09
0.1 0.001
INPUT-OUTPUT VOLTAGE (V)
0.01 0.1 OUTPUT-INPUT VOLTAGE (V)
1
6652 G10
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LTC6652
Characteristic curves are similar for most LTC6652s. Curves from the LTC6652-1.25, LTC6652-2.5 and the LTC6652-5 represent the extremes and typical of the voltage options. Characteristic curves for other output voltages fall between these curves and can be estimated based on their output. 2.5V Low Frequency 0.1Hz to 10Hz Transient Noise
600 500 OUTPUT NOISE (1V/DIV) NOISE VOLTAGE (nV/Hz) 400 300 200 100 0 0.01
6652 G11
TYPICAL PERFORMANCE CHARACTERISTICS
2.5V Output Voltage Noise Spectrum
TIME (1 SECOND/DIV)
0.1 1 FREQUENCY (kHz)
10
6652 G12
Typical VOUT Distribution for LTC6652-2.5
180 160 OUTPUT CAPACITOR 140 NUMBER OF UNITS 120 80 60 40 20 0 2.4985 2.4995 2.5005 OUTPUT VOLTAGE (V) 2.5015
6652 G15
Stability with Output Capacitance (LTC6652-2.5, LTC6652-3, LTC6652-3.3, LTC6652-4.906, LTC6652-5)
10F 1F
1004 UNITS
LTC6652A LIMITS 0.1F 10nF REGION OF MARGINAL STABILITY 1nF 100pF NO CAP -5 0 LOAD CURRENT (mA) 5
6652 G14
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LTC6652
Characteristic curves are similar for most LTC6652s. Curves from the LTC6652-1.25, LTC6652-2.5 and the LTC6652-5 represent the extremes and typical of the voltage options. Characteristic curves for other output voltages fall between these curves and can be estimated based on their output. 5V Output Voltage Temperature Drift
5.005 3 TYPICAL PARTS 5.002
TYPICAL PERFORMANCE CHARACTERISTICS
5V Line Regulation
5V Supply Current vs Input Voltage
1000 900
REFERENCE VOLTAGE (V)
SUPPLY CURRENT (A)
OUTPUT VOLTAGE (V)
5.003
5.001 25C 5.000 125C 4.999 -40C
800 700 600 500 400 300 200 100 125C 25C -40C
5.000
4.998
4.995 -50 -25
4.998 0 25 50 75 100 125 150 TEMPERATURE (C)
6652 G25
0
2
8 6 10 4 INPUT VOLTAGE (V)
12
14
6652 G26
0 0 2
8 6 4 10 INPUT VOLTAGE (V)
12
14
6652 G27
5V Shutdown Current vs Input Voltage
1.0 0.9 0.8 SUPPLY CURRENT (A) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 2 25C 8 6 4 10 INPUT VOLTAGE (V) 12 14 -40C 125C 1 10
5V Minimum VIN to VOUT Differential (Sourcing)
5V Low Frequency 0.1Hz to 10Hz Transient Noise
25C
0.1 -40C 125C 0.01 0.001 0.01 0.1 1
6652 G30
OUTPUT NOISE (5V/DIV)
OUTPUT CURRENT (mA)
TIME (1 SECOND/DIV)
6652 G31
INPUT-OUTPUT VOLTAGE (V)
6652 G29
5V Output Voltage Noise Spectrum
1000 VIN 2V/DIV
5V Start-Up Response Without Output Capacitor
VIN 2V/DIV
5V Start-Up Response with Output Capacitor
NOISE VOLTAGE (nV/Hz)
800
600 VOUT 2V/DIV VOUT 2V/DIV
400
200 100s/DIV COUT = 0F 0 0.01 0.1 1 FREQUENCY (kHz) 10
6652 G32
6652 G33
100s/DIV COUT = 1F
6652 G34
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LTC6652
Characteristic curves are similar for most LTC6652s. Curves from the LTC6652-1.25, LTC6652-2.5 and the LTC6652-5 represent the extremes and typical of the voltage options. Characteristic curves for other output voltages fall between these curves and can be estimated based on their output. Power Supply Rejection Ratio vs Frequency
0 POWER SUPPLY REJECTION RATIO (dB) -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 0.01 0.1 1 10 FREQUENCY (kHz) 100 1000
6652 G07
TYPICAL PERFORMANCE CHARACTERISTICS
Output Impedance vs Frequency
100 COUT = 0F 2.5
SHDN Input Voltage Thresholds vs VIN
COUT = 0F OUTPUT IMPEDANCE ()
2.0 10 VTRIP (V) 1.5 COUT = 1F COUT = 10F 1 0.5
VTH(UP)
COUT = 1F
VTH(DN) 1.0
COUT = 10F
0.1 0.01
0 0.1 1 10 FREQUENCY (kHz) 100
6652 G08
2
4
6
8 VIN (V)
10
12
14
6652 G13
PIN FUNCTIONS
DNC (Pin 1): Do Not Connect. VIN (Pin 2): Power Supply. The minimum supply input is VOUT + 300mV or 2.7V; whichever is higher. The maximum supply is 13.2V. Bypassing VIN with a 0.1F capacitor to GND will improve PSRR. SHDN (Pin 3): Shutdown Input. This active low input powers down the device to <2A. For normal operation tie this pin to VIN. GND (Pin 4): Device Ground. VOUT (Pin 6): Output Voltage. An output capacitor is not required. For some applications, a capacitor between 0.1F to 10F can be beneficial. See the graphs in the Typical Performance Characteristics section for further details. GND (Pins 5,7,8): Internal function. Ground these pins.
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LTC6652 BLOCK DIAGRAM
2 VIN
3
SHDN
+
BANDGAP
VOUT
6
-
4
GND
6652 BD
APPLICATIONS INFORMATION
Bypass and Load Capacitors The LTC6652 voltage references do not require an input capacitor, but a 0.1F capacitor located close to the part improves power supply rejection. The LTC6652 voltage references are stable with or without a capacitive load. For applications where an output capacitor is beneficial, a value of 0.1F to 10F is recommended depending on load conditions. The Typical Performance Characteristics section includes a plot illustrating a region of marginal stability. Either no or low value capacitors for any load current are acceptable. For loads that sink current or light loads that source current, a 0.1F to 10F capacitor has stable operation. For heavier loads that source current a 0.5F to 10F capacitor range is recommended. The transient response for a 0.5V step on VIN with and without an output capacitor is shown in Figures 2 and 3, respectively. The LTC6652 references with an output of 2.5V and above are guaranteed to source and sink 5mA. The 1.25V and 2.048V versions are guaranteed to source 5mA and sink 1mA. The test circuit for transient load step response is shown in Figure 1. Figures 4 and 5 show a 5mA source and sink load step response without a load capacitor, respectively. Start-Up The start-up characteristic of the LTC6652 is shown in Figures 8 and 9. Note that the turn-on time is affected by the value of the output capacitor.
VIN 3V CIN 0.1F 2, 3 6 100 COUT 1F 4, 5, 7, 8
6652 F01
LTC6652-2.5
VGEN
0.5V
Figure 1. Transient Load Test Circuit
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LTC6652 APPLICATIONS INFORMATION
3.5V VIN 5mA 3V IOUT 0mA
VOUT 500mV/DIV
VOUT 200mV/DIV
COUT = 0F
500s/DIV
6652 F02
COUT = 0F
250s/DIV
6652 F05
Figure 2. Transient Response Without Output Capacitor
Figure 5. LTC6652-2.5 Sinking Current Without Output Capacitor
VIN
3.5V 3V
0mA IOUT -5mA
VOUT 500mV/DIV
VOUT 200mV/DIV
COUT = 1F
500s/DIV
6652 F03
COUT = 1F
250s/DIV
6652 F06
Figure 3. Transient Response with 1F Output Capacitor
Figure 6. LTC6652-2.5 Sourcing Current with Output Capacitor
0mA IOUT -5mA
5mA IOUT 0mA
VOUT 200mV/DIV
VOUT 50mV/DIV
COUT = 0F
250s/DIV
6652 F04
COUT = 1F
250s/DIV
6652 F07
Figure 4. LTC6652-2.5 Sourcing Current Without Output Capacitor
Figure 7. LTC6652-2.5 Sinking Current with Output Capacitor
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LTC6652 APPLICATIONS INFORMATION
2.8V VIN 2V/DIV VIN 13.2V C1 1F R1 20k VIN LTC6652-2.5 SHDN GND VOUT 1V/DIV TO C 2N7002
6652 F10
VOUT
VOUT C2 1F
COUT = 0F
100s/DIV
6652 F08
Figure 10. Open-Drain Shutdown Circuit
Figure 8. Start-Up Response Without Output Capacitor
SHDN 1V/DIV VIN 2V/DIV
VOUT 1V/DIV VOUT 1V/DIV ILOAD = 5mA
6652 F09
1ms/DIV
6652 F11
COUT = 1F
100s/DIV
Figure 11. Shutdown Response with 5mA Load
Figure 9. Start-Up Response with 1F Output Capacitor
In Figure 8, ripple momentarily appears just after the leading edge of powering on. This brief one time event is caused by calibration circuitry during initialization. When an output capacitor is used, the ripple is virtually undetectable as shown in Figure 9. Shutdown Mode Shutdown mode is enabled by tying SHDN low which places the part in a low power state (i.e., <2A). In shutdown mode, the output pin takes the value 20k * (rated output voltage). For example, an LTC6652-2.5 will have an output impedance of 20k * 2.5 = 50k. For normal operation, SHDN should be greater than or equal to 2.0V. For use with a microcontroller, use a pull-up resistor to VIN and an open-drain output driver as shown in Figure 10. The LTC6652's response into and out of shutdown mode is shown in Figure 11.
The trip thresholds on SHDN have some dependence on the voltage applied to VIN as shown in the Typical Performance Characteristics section. Be careful to avoid leaving SHDN at a voltage between the thresholds as this will likely cause an increase in supply current due to shoot-through current. Long-Term Drift Long-term drift cannot be extrapolated from accelerated high temperature testing. This erroneous technique gives drift numbers that are wildly optimistic. The only way long-term drift can be determined is to measure it over the time interval of interest. The LTC6652 long-term drift data was collected on more than 100 parts that were soldered into PC boards similar to a "real world" application. The boards were then placed into a constant temperature oven with TA = 35C, their outputs were scanned regularly and measured with an 8.5 digit DVM. Long-term drift is shown below in Figure 12.
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LTC6652 APPLICATIONS INFORMATION
80 LTC6652-2.5 MS8 PACKAGE 3 TYPICAL PARTS 60 TA = 35 C 40 ppm 20 0 -20 -40 0 300 900 600 HOURS 1200 1500
6652 F12
35 125C TO 25C 30 NUMBER OF UNITS 25 20 15 10 5 0 -250 -40C TO 25C
50 -150 -50 DISTRIBUTION (ppm)
150
6652 F13
Figure 12. Long Term Drift
Figure 13. Hysteresis Plot -40C to 125C
Hysteresis The hysteresis data shown in Figure 13 represents the worst-case data collected on parts from -40C to 125C. The output is capable of dissipating relatively high power, i.e., for the LT6652-2.5, PD = 10.7V * 5.5mA = 58.85mW. The thermal resistance of the MS8 package is 200C/W and this dissipation causes a 11.8C internal rise. This could increase the junction temperature above 125C and may cause the output to shift due to thermal hysteresis. PC Board Layout The mechanical stress of soldering a surface mount voltage reference to a PC board can cause the output voltage to shift and temperature coefficient to change. These two changes are not correlated. For example, the voltage may shift, but the temperature coefficient may not. To reduce the effects of stress-related shifts, mount the reference near the short edge of the PC board or in a corner. In addition, slots can be cut into the board on two sides of the device. The capacitors should be mounted close to the package. The GND and VOUT traces should be as short as possible to minimize I * R drops. Excessive trace resistance directly impacts load regulation.
IR Reflow Shift The different expansion and contraction rates of the materials that make up the lead-free LTC6652 package cause the output voltage to shift after undergoing IR reflow. Leadfree reflow profiles reach over 250C, considerably more than their leaded counterparts. The lead-free IR reflow profile used to experimentally measure output voltage shift in the LTC6652-2.5 is shown in Figure 14. Similar results can be expected using a convection reflow oven. In our experiment, the serialized parts were run through the reflow process twice. The results indicate that the standard deviation of the output voltage increases with a slight positive mean shift of 0.003% as shown in Figure 15. While there can be up to 0.016% of output voltage shift, the overall drift of the LTC6652 after IR reflow does not vary significantly. Power Dissipation Power dissipation in the LTC6652 is dependent on VIN, load current, and package. The LTC6652 package has a thermal resistance, or JA, of 200C/W. A curve that illustrates allowed power dissipation vs temperature for this package is shown in Figure 16. The power dissipation of the LTC6652-2.5V as a function of input voltage is shown in Figure 17. The top curve shows power dissipation with a 5mA load and the bottom
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12
LTC6652 APPLICATIONS INFORMATION
curve shows power dissipation with no load. When operated within its specified limits of VIN = 13.2V and sourcing 5mA, the LTC6652-2.5 consumes just under 60mW at room temperature. At 125C the quiescent cur300 380s TP = 260C
rent will be slightly higher and the power consumption increases to just over 60mW. The power-derating curve in Figure 16 shows the LTC6652-2.5 can safely dissipate 125mW at 125C about half the maximum power consumption of the package.
0.7 0.6 0.5 0.4 0.3 0.2
225
TS = 190C 150 T = 150C RAMP TO 150C 75 120s 0 0 2 4 6 MINUTES
tP 30s tL 130s 40s
DISSIPATION (W)
TL = 217C TS(MAX) = 200C
RAMP DOWN
0.1 0 8 10
6652 F14
0
20
40 60 80 100 TEMPERATURE (C)
120
140
6652 F16
Figure 14. Lead-Free Reflow Profile
Figure 16. Maximum Recommended Dissipation for LTC6652
10
0.06 0.05 0.04
TA = 25C
8 NUMBER OF UNITS
6
POWER (W)
5mA LOAD 0.03 0.02
4
2
0.01 NO LOAD 0 2 4 6 8 VIN (V) 10 12 14
6652 F17
0
0.002 0.010 0.018 -0.014 -0.006 OUTPUT VOLTAGE SHIFT DUE TO IR REFLOW (%)
6652 F15
Figure 15. Output Voltage Shift Due to IR Reflow
Figure 17. Typical Power Dissipation of the LTC6652
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13
LTC6652 TYPICAL APPLICATIONS
Extended Supply Range Reference
4V TO 30V R1 VIN BZX84C18 SHDN C1 0.1F LTC6652-2.5 VOUT GND
6652 TA02
Extended Supply Range Reference
6V TO 160V R1 330k VOUT VIN C2 OPTIONAL BZX84C18 C1 0.1F SHDN VOUT C2 OPTIONAL R2 4.7k ON SEMI MMBT5551
LTC6652-2.5 VOUT GND
6652 TA03
Negative Rail Circuit
V+ 2, 3, 6 LTC6652-2.5 (VOUT + 1.8V)
Boosted Output Current
C1 1F
R1 220 2N2905 VIN SHDN VOUT C2 1F
6652 TA04
6652 TA06
4, 5, 7, 8 -2.5V 100 -3.5V 1F LTC6652-2.5 VOUT GND
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14
LTC6652 PACKAGE DESCRIPTION
MS8 Package 8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660 Rev F)
0.889 0.127 (.035 .005)
5.23 (.206) MIN
3.20 - 3.45 (.126 - .136)
0.42 0.038 (.0165 .0015) TYP
0.65 (.0256) BSC
3.00 0.102 (.118 .004) (NOTE 3)
8
7 65
0.52 (.0205) REF
RECOMMENDED SOLDER PAD LAYOUT
DETAIL "A" 0 - 6 TYP 4.90 0.152 (.193 .006) 3.00 0.102 (.118 .004) (NOTE 4)
0.254 (.010) GAUGE PLANE
1 0.53 0.152 (.021 .006) DETAIL "A" 0.18 (.007) SEATING PLANE 0.22 - 0.38 (.009 - .015) TYP 1.10 (.043) MAX
23
4 0.86 (.034) REF
NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.65 (.0256) BSC
0.1016 0.0508 (.004 .002)
MSOP (MS8) 0307 REV F
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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.
15
LTC6652 TYPICAL APPLICATION
Improved Reference Supply Rejection in a Data Converter Application
LTC1657 16 VCC DATA GND R1 50k VIN VOUT LTC6652 SHDN C1 0.1F C2 10F GND COUT 1F V1 V2 V3 V4 REF A/D GND LTC1605 16 DOUT D/A VDAC
REF
6652 TA05
RELATED PARTS
PART NUMBER LT1460 LT1461 LT1790 LT6650 LT6660 DESCRIPTION Micropower Series References Micropower Series Low Dropout Micropower Precision Series References Micropower Reference with Buffer Amplifier Tiny Micropower Series Reference COMMENTS 0.075% Max, 10ppm/C Max, 20mA Output Current 0.04% Max, 3ppm/C Max, 50mA Output Current 0.05% Max, 10ppm/C Max, 60A Supply, SOT23 Package 0.5% Max, 5.6A Supply, SOT23 Package 0.2% Max, 20ppm/C Max, 20mA Output Current, 2mm x 2mm DFN
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16 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 1208 REV B * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2007

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