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LT3092

3092fb

TYPICAL APPLICATION

DESCRIPTION

200mA 2-Terminal

Programmable Current Source

The LT

3092 is a programmable 2-terminal current

source. It requires only two resistors to set an output

current between 0.5mA and 200mA. A multitude of analog

techniques lend themselves to actively programming the

output current. The LT3092 is stable without input and

output capacitors, offering high DC and AC impedance. This

feature allows operation in intrinsically safe applications.

The SET pin features 1% initial accuracy and low tem-

perature coefﬁ cient. Current regulation is better than

10ppm/V from 1.5V to 40V.

The LT3092 can operate in a 2-terminal current source

conﬁ guration in series with signal lines. It is ideal for driv-

ing sensors, remote supplies, and as a precision current

limiter for local supplies.

Internal protection circuitry includes reverse-battery and

reverse-current protection, current limiting and thermal

limiting. The LT3092 is offered in the 8-lead TSOT-23,

3-lead SOT-223 and 8-lead 3mm × 3mm DFN packages.

Adjustable 2-Terminal Current Source

FEATURES

APPLICATIONS

Programmable 2-Terminal Current Source

Maximum Output Current: 200mA

Wide Input Voltage Range: 1.2V to 40V

Input/Output Capacitors Not Required

Resistor Ratio Sets Output Current

Initial Set Pin Current Accuracy: 1%

Reverse-Voltage Protection

Reverse-Current Protection

<0.001%/V Line Regulation Typical

Current Limit and Thermal Shutdown Protection

Available in 8-Lead SOT-23, 3-Lead SOT-223 and

8-Lead 3mm × 3mm DFN Packages

2-Terminal Floating Current Source

GND Referred Current Source

Variable Current Source

In-Line Limiter

Intrinsic Safety Circuits

SET Pin Current vs Temperature

3092 TA01a

SET OUT

–

LT3092

10µA

OUT

SET

– V

OUT

= 1.2V TO 40V

IµA

SOURCE

SET

OUT

= 10 •

TEMPERATURE (°C)

–50

9.900

SET PIN CURRENT (µA)

9.950

10.000

10.050

–25

25 50 10075 125

10.100

9.925

9.975

10.025

10.075

150

3092 TA01b

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.

Summary of content (22 pages)

PAGE 1
LT3092 200mA 2-Terminal Programmable Current Source FEATURES DESCRIPTION n The LT®3092 is a programmable 2-terminal current source. It requires only two resistors to set an output current between 0.5mA and 200mA. A multitude of analog techniques lend themselves to actively programming the output current. The LT3092 is stable without input and output capacitors, offering high DC and AC impedance. This feature allows operation in intrinsically safe applications.
PAGE 2
LT3092 ABSOLUTE MAXIMUM RATINGS (Note 1) All Voltages Relative to VOUT IN Pin Voltage Relative to SET, OUT ........................±40V SET Pin Current (Note 6) .....................................±15mA SET Pin Voltage (Relative to OUT, Note 6) ...............±10V Output Short-Circuit Duration .......................... Indeﬁnite Operating Junction Temperature Range (Notes 2, 8) E, I Grades ......................................... –40°C to 125°C MP Grade...........................................
PAGE 3
LT3092 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TJ = 25°C. (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS 10 10 10.1 10.2 μA μA 2 4 mV mV –0.1 –0.5 –2 nA mV 0.03 0.003 0.2 0.010 SET Pin Current ISET VIN = 2V, ILOAD = 1mA 2V ≤ VIN ≤ 40V, 1mA ≤ ILOAD ≤ 200mA l 9.9 9.
PAGE 4
LT3092 TYPICAL PERFORMANCE CHARACTERISTICS SET Pin Current SET Pin Current Distribution Offset Voltage (VOUT – VSET) 2.0 N = 1326 10.075 1.5 10.050 1.0 OFFSET VOLTAGE (mV) SET PIN CURRENT (μA) 10.100 10.025 10.000 9.975 9.950 9.925 9.900 –50 –25 0.5 0.0 –0.5 –1.0 –1.5 0 25 50 75 100 125 150 TEMPERATURE (°C) 3092 G01 10 10.20 9.90 10.10 SET PIN CURRENT DISTRIBUTION (μA) 9.80 –2.
PAGE 5
LT3092 TYPICAL PERFORMANCE CHARACTERISTICS Dropout Voltage Minimum Output Current 400 300 200 100 0 25 50 75 100 125 150 TEMPERATURE (°C) 3092 G08 DROPOUT VOLTAGE (VIN – VOUT) (V) DROPOUT VOLTAGE (VIN – VOUT) (V) 500 1.4 TJ = –55°C 1.2 TJ = 25°C 1.0 TJ = 125°C 0.8 0.6 0.4 0.2 0 0 25 50 75 100 125 150 175 200 LOAD CURRENT (mA) 1.2 ILOAD = 200mA 1.0 ILOAD = 100mA 0.8 0.6 0.4 0.
PAGE 6
LT3092 TYPICAL PERFORMANCE CHARACTERISTICS Turn-On Response 6 INPUT VOLTAGE (V) INPUT VOLTAGE (V) Turn-On Response 8 1mA CURRENT SOURCE CONFIGURATION 4 2 0 0 0 5 2 15 0 10 5 0 10 15 20 25 30 35 40 45 50 TIME (μs) 10mA CURRENT SOURCE CONFIGURATION 4 0 10 15 20 25 30 35 40 45 50 TIME (μs) 3092 G15 Residual Output for Less Than Minimum Output Current 3092 G16 Output Impedance 1G 800 SET PIN = 0V VIN 600 100M VOUT VIN = 36V OUTPUT IMPEDANCE (Ω) 700 OUTPUT VOLTAGE (mV) 5 OUTPUT CURRENT
PAGE 7
LT3092 PIN FUNCTIONS (DD/ST/TS8) IN (Pins 7, 8/Pin 3/Pins 7, 8): Input. This pin supplies power to bias internal circuitry and supply output load current. For the device to operate properly and regulate, the voltage on this pin must be 1.2V to 1.4V above the OUT pin (depending on output load current—see the dropout voltage speciﬁcations in the Electrical Characteristics table). NC (Pins 3, 5, 6/NA/Pins 1, 6): No Connection.
PAGE 8
LT3092 APPLICATIONS INFORMATION Introduction The LT3092 is a versatile IC that operates as a 2-terminal programmable current source with the addition of only two external resistors; no external bypass capacitors are needed for stability. The LT3092 is easy to use and has all the protection features expected in high performance products. Included are reverse-voltage protection, reverse-current protection, short-circuit protection and thermal shutdown with hysteresis.
PAGE 9
LT3092 APPLICATIONS INFORMATION From this point, selecting ROUT is easy, as it is a straightforward calculation from RSET. Take note, however, resistor errors must be accounted for as well. While larger voltage drops across RSET minimize the error due to offset, they also increase the required operating headroom. Obtaining the best temperature coefﬁcient does not require the use of expensive resistors with low ppm temperature coefﬁcients.
PAGE 10
LT3092 APPLICATIONS INFORMATION Figure 3 depicts the simplest frequency compensation network as a single capacitor connected across the two terminals of the current source. In this case, either a capacitor with a value less than 1000pF, or greater than 1μF (ESR < 0.5Ω), may stabilize the circuit. Some applications may use the small value capacitor to stand off DC voltage, but allow the transfer of data down a signal line.
PAGE 11
LT3092 APPLICATIONS INFORMATION capacitor on the lower impedance output, and the same restrictions do not apply. Capacitors in the range of 0.1μF to 1μF usually provide sufﬁcient bypassing on the input, and the value of input capacitance may be increased without limit. If an application uses GND referred capacitors on the input or output (particularly the input), pay attention to the length of the lines powering and returning ground from the circuit.
PAGE 12
LT3092 APPLICATIONS INFORMATION Quieting the Noise Paralleling Devices When a reduction in the noise of the current source is desired, a small capacitor can be placed across RSET (CSET in Figure 7). Normally, the 10μA reference current source generates noise current levels of 2.7pA/√Hz (0.7nARMS over the 10Hz to 100kHz bandwidth). The SET pin resistor generates a spot noise equal to in = √4kT/R (k = Boltzmann’s constant, 1.
PAGE 13
LT3092 APPLICATIONS INFORMATION IOUT IN LT3092 IN LT3092 10μA 300Ω 10μA 300Ω + – + – SET OUT 20k OUT 1.33Ω SET 1.33Ω 20k 3092 F08 IOUT, 300mA Figure 8. Connect Two LT3092s for Higher Current IOUT LT3092 LT3092 IN 10μA IN + – SET 1V Rx 10μA + – 40mΩ* Rx = VIN(MAX ) • R 90 % 40mΩ* SET R 2.5Ω 50k 3092 F09 *40mΩ PC BOARD TRACE IOUT, 400mA Figure 9. Parallel Devices interface, heat sink resistance or circuit board-to-ambient as the application dictates.
PAGE 14
LT3092 APPLICATIONS INFORMATION Demo circuit 1531A’s board layout using multiple inner VOUT planes and multiple thermal vias achieves 28°C/W performance for the DFN package. VOUT(MIN CONTINUOUS) = 11.4V (12V – 5%) IOUT = 200mA Table 2. DD Package, 8-Lead DFN COPPER AREA VIN(MAX CONTINUOUS) = 16.
PAGE 15
LT3092 TYPICAL APPLICATIONS Paralleling Current Sources for Higher Current IN LT3092 IN LT3092 Paralleling LT3092s with Ballast Resistor IN LT3092 IN LT3092 10μA 10μA 10μA 10μA + – + – + – + – SET OUT R2 SET R1 OUT R4 SET OUT SET OUT R1 40mΩ R3 R3 40mΩ 3092 TA02 ⎛ R2 R4 ⎞ IOUT = 10µA • ⎜ + ⎝ R1 R3 ⎟⎠ IOUT R4 2Ω R2 40.
PAGE 16
LT3092 TYPICAL APPLICATIONS Remote Temperature Sensor DAC Controlled Current Source IOUT = 0.5mA TO 100mA VIN IN LT3092 V+ IN LT3092 IN LT3092 10μA 10μA 10μA + – + – + – SET OUT 49.9k MURATA NCP15WF104F03RC 1% 100k Active Load SET DAC OUTPUT 0V TO 1V 49.
PAGE 17
LT3092 TYPICAL APPLICATIONS 2-Terminal AC Current Limiter Pulsed Current Source, Load to VIN VIN LOAD IOUT IN LT3092 LT3092 10μA 10μA + – IOUT + – SET OUT 20k 1Ω 20k IOUT R 0 . 2V IOUT IOUT ISET 3092 TA13 OFF ON 3092 TA12 High Accuracy Current Source Voltage Clamp VIN 10μA 10μA + – OUT 4.99Ω 10k SET 10k + – VOUT SET OUT 100k LT1634-1.25 10V 2N3906 3092 TA14 2N3904 10k IN LT3092 IN LT3092 10mA IOUT 124Ω 0.
PAGE 18
LT3092 TYPICAL APPLICATIONS 2-Level Current Source VIN IN LT3092 10μA + – SET OUT 100k 4.99Ω 100k* 10V* VN2222LL* 10k* VOUT IOUT = 200mA, IF VIN – VOUT < 12V = 100mA, IF VIN – VOUT > 12V *CURRENT FOLDBACK CIRCUIT LIMITS THE LT3092 POWER DISSIPATION 3092 TA16 More Efﬁcient Current Source 0.
PAGE 19
LT3092 PACKAGE DESCRIPTION DD Package 8-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1698) R = 0.115 TYP 5 0.38 ± 0.10 8 0.675 ±0.05 3.5 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) 3.00 ±0.10 (4 SIDES) PACKAGE OUTLINE 1.65 ± 0.10 (2 SIDES) PIN 1 TOP MARK (NOTE 6) (DD) DFN 1203 0.25 ± 0.05 0.75 ±0.05 0.200 REF 0.50 BSC 4 0.25 ± 0.05 2.38 ±0.05 (2 SIDES) 1 0.50 BSC 2.38 ±0.10 (2 SIDES) 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1.
PAGE 20
LT3092 PACKAGE DESCRIPTION TS8 Package 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637) 0.52 MAX 2.90 BSC (NOTE 4) 0.65 REF 1.22 REF 1.4 MIN 3.85 MAX 2.62 REF 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.22 – 0.36 8 PLCS (NOTE 3) 0.65 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) 1.95 BSC TS8 TSOT-23 0802 NOTE: 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 1. DIMENSIONS ARE IN MILLIMETERS 6.
PAGE 21
LT3092 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 12/09 Update Order Information 2 3092fb 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.
PAGE 22
LT3092 TYPICAL APPLICATIONS USB LED Driver Current Limiter for Remote Power VIN USB IN LT3092 IN LT3092 10μA 10μA + – + – SET SET OUT OUT 100k ADJUST LIMIT 1Ω 4.99Ω LDO 20k VOUT 200mA LED 3092 TA18 3092 TA19 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1761 100mA, Low Noise LDO 300mV Dropout Voltage, Low Noise: 20μVRMS, VIN = 1.8V to 20V, ThinSOT™ Package LT1762 150mA, Low Noise LDO 300mV Dropout Voltage, Low Noise: 20μVRMS, VIN = 1.