Catalogs >
ADI >
LT3092 - 200mA 2-Terminal Programmable Current Source

LT3092 - 200mA 2-Terminal Programmable Current Source
22Pages

Catalog excerpts

LT3092 - 200mA 2-Terminal Programmable Current Source - 1

LT3092 1 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 temperature 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 driving 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 n Programmable 2-Terminal Current Source n Maximum Output Current: 200mA n Wide Input Voltage Range: 1.2V to 40V n Input/Output Capacitors Not Required n Resistor Ratio Sets Output Current n Initial Set Pin Current Accuracy: 1% n Reverse-Voltage Protection n Reverse-Current Protection n <0.001%/V Line Regulation Typical n Current Limit and Thermal Shutdown Protection n Available in 8-Lead SOT-23, 3-Lead SOT-223 and 8-Lead 3mm × 3mm DFN Packages n 2-Terminal Floating Current Source n GND Referred Current Source n Variable Current Source n In-Line Limiter n Intrinsic Safety Circuits SET Pin Current vs Temperature 3092 TA01a IN SET OUT + – LT3092 10ìA RSET ROUT VIN – VOUT = 1.2V TO 40V I ìA R SOURCE R SET OUT = 10 • TEMPERATURE (°C) –50 9.900 SET PIN CURRENT (ìA) 9.950 10.000 10.050 –25 0 25 50 75 100 125 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.

Open the catalog to page 1

LT3092 - 200mA 2-Terminal Programmable Current Source - 3

LT3092 3 3092fb ELECTRICAL CHARACTERISTICS 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: Unless otherwise specifi ed, all voltages are with respect to VOUT. The LT3092E is tested and specifi ed under pulse load conditions such that TJ TA. The LT3092E is 100% tested at TA = 25°C. Performance at –40°C and 125°C is assured by design, characterization, and correlation with statistical process controls. The...

Open the catalog to page 3

LT3092 - 200mA 2-Terminal Programmable Current Source - 7

LT3092 7 3092fb 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 specifi cations in the Electrical Characteristics table). NC (Pins 3, 5, 6/NA/Pins 1, 6): No Connection. These pins have no connection to internal circuitry and may be tied to IN, OUT, GND or fl oated. OUT (Pins 1, 2/Pin 2/Pins 2, 3, 4): Output. This is the power...

Open the catalog to page 7

LT3092 - 200mA 2-Terminal Programmable Current Source - 8

LT3092 8 3092fb 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. The LT3092 operates with or without input and output capacitors. The simplest current source application requires only two discrete resistors...

Open the catalog to page 8

LT3092 - 200mA 2-Terminal Programmable Current Source - 9

LT3092 9 3092fb APPLICATIONS INFORMATION inductive components and may be complex distributed networks. In addition, the current source’s value will differ between applications and its connection may be GND referenced, power supply referenced or fl oating in a signal line path. Linear Technology strongly recommends that stability be tested in situ for any LT3092 application. In LT3092 applications with long wires or PCB traces, the inductive reactance may cause instability. In some cases, adding series resistance to the input and output lines (as shown in Figure 2) may suffi ciently dampen...

Open the catalog to page 9

LT3092 - 200mA 2-Terminal Programmable Current Source - 10

LT3092 10 3092fb 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 1ìF (ESR < 0.5Ù), 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. For some applications, this capacitance range may be unacceptable or present a design constraint. One circuit example typifying this is an “intrinsically-safe”...

Open the catalog to page 10

LT3092 - 200mA 2-Terminal Programmable Current Source - 11

LT3092 11 3092fb APPLICATIONS INFORMATION capacitor on the lower impedance output, and the same restrictions do not apply. Capacitors in the range of 0.1ìF to 1ìF usually provide suffi cient 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. In the case where long power supply and return lines are coupled with low ESR input capacitors, application-specifi c voltage...

Open the catalog to page 11

LT3092 - 200mA 2-Terminal Programmable Current Source - 12

LT3092 12 3092fb APPLICATIONS INFORMATION Quieting the Noise 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 10ìA reference current source generates noise current levels of 2.7pA/ãHz (0.7nARMS over the 10Hz to 100kHz bandwidth). The SET pin resistor generates a spot noise equal to in = ã4kT/R (k = Boltzmann’s constant, 1.38 • 10–23J/°K, and T is absolute temperature) which is RMS-summed with the noise generated by the 10ìA reference current source. Placing a CSET capacitor across RSET (as shown in...

Open the catalog to page 12