feature

Ultra-compact SC70 and SOT-23 packages; low temperature coefficient: 75 ppm/°C (max) pin compatible with LM4040 /LM4050; initial accuracy: ±0.1%; no external capacitors required; wide operating current range: 50µA to 15mA; Extended Temperature Range: -40°C to + 125 °C for automotive applications.

application

Portable battery powered equipment; automotive electronics; power supplies; data acquisition systems; instrumentation and process control; energy management.

General Instructions

Designed for space critical applications, the ADR5040 /ADR5041/ADR5043/ADR5044/ADR5045 feature high precision shunt voltage references and are housed in Ultrasmall SC70 and SOT-23 packages. These voltage references are versatile, easy-to-use references that can be used in a wide variety of applications. It is characterized by low temperature drift, initial accuracy better than 0.1%, and fast settling time.

With output voltages of 2.048 V, 2.5 V, 3.0 V, 4.096 V, and 5.0 V, the advanced design of the ADR5040/ADR5041/ADR5043/ADR5044/ADR5045 eliminates the need for external capacitor compensation, but the reference voltage is stable with any capacitive load . The minimum operating current is increased from 50µA to a maximum of 15mA. This low operating current and ease of use make these references ideal for handheld, battery powered applications. This series of references features an extended temperature range of -40°C to +125°C. The ADR5041W and ADR5044W are qualified for automotive applications and are available in a 3-lead SOT-23 package.

theory of operation

The ADR504X family uses the bandgap concept to generate stable, low temperature coefficient voltage references suitable for high precision data acquisition components and systems. These devices take advantage of the physical properties of silicon transistor base-emitter voltages in the forward-biased operating region. All such transistors have a temperature coefficient (TC) of about 2 mV/°C, making them unsuitable for direct use as low temperature coefficient references. However, extrapolating the temperature characteristics of any of these devices to absolute zero (absolute temperature proportional to collector current) reveals that its V is approximately close to the silicon bandgap voltage. Therefore, if the voltage develops as a sum of v with opposite temperature coefficients, a zero temperature coefficient reference results.

application information

The ADR5040/ADR5041/ADR5043/ADR5044/ADR5045 are a family of precision shunt voltage references. They are designed to work without external capacitors between positive and negative. If a bypass capacitor is used to filter the supply, the reference remains stable.

For voltage regulation, all shunt voltage references require an external bias resistor (R) between the supply voltage and the reference voltage (see Figure 19). r sets the current flowing through the load (i) and reference (i). Since the load and supply voltages may be different, RNEED should be selected based on the following considerations:

(1), R must be small enough to provide the minimum current to the ADR5040/ADR5041/ADR5043/ADR5044/ADR5045, even when the supply voltage is at its minimum value and the load current is at its maximum value.

(2), R must be large enough that I do not exceed 15 mA when the supply voltage is at its maximum value and the load current is at its minimum value.

Under these conditions, R is determined by the supply voltage (V), the ADR5040/ADR5041/ADR5043/ADR5044/Bias S Corporation ADR5045 load and operating current (I), and the ADR5040/ADR5041/ADR5043/ADR5044/ADR5045 output voltage (V).

Precision Negative Voltage Reference

The ADR5040/ADR5041/ADR5043/ADR5044/ADR5045 are suitable for applications requiring precise negative voltages. Figure 20 shows the ADR5045 configured to provide a negative output. Care should be taken when using low temperature sensitive resistors to avoid resistor errors.

Stack ADR504X for user definable output

Multiple ADR504x parts can be stacked together to allow the user to obtain the higher voltage required. Figure 21a shows three ADR5045 devices configured to supply 15V. The bias resistor R is chosen using Equation 3, noting that the same bias current flows through all parallel references in series. Figure 21b shows three ADR5045 devices stacked together to generate -15 V. R is calculated in the same way as before. Parts of different voltages can also be added together; that is, the adr5041 and adr5045 can be added together to provide an output of +7.5 V or -7.5 V as required. Note, however, that the initial accuracy error is the sum of the errors of all stacked parts, as is the variation in temperature coefficient and output voltage with input current.

Adjustable Precision Voltage Source

The ADR5040/ADR5041/ADR5043/ADR5044/ADR5045, combined with a precision low input bias op amp, such as the AD8610, can be used to output a precisely adjustable voltage. Figure 22 illustrates the implementation of this application using the ADR5040/ADR5041/ADR5043/ADR5044/ADR5045.

The output of the op amp, vout, is determined by the gain of the circuit, which depends entirely on the resistors r1 and r2.

VOUT = (1 + R2/R1)VREF

Another capacitor c1 in parallel with r2 can be used to filter out high frequency noise. The value of c1 depends on the value of r2.

Programmable Current Source

Using a few ultra-small and inexpensive components, a programmable current source can be constructed, as shown in Figure 23. A constant voltage on the gate of the transistor sets the current through the load. Changing the voltage on the gate changes the current. The AD5247 is a digital potentiometer with an IC® digital interface and the AD8601 is a precision rail-to-rail input operational amplifier. Each increment of the digital potentiometer increases or decreases the voltage at the non-rotating input of the op amp. Therefore, this voltage varies with the reference voltage.