概要

The AD5290 is one of the few high voltage, high performance, and compact digital potentiometers in the market at present. This device can be used as a programmable resistor or resistor divider. The AD5290 performs the same electronic adjustment function as mechanical potentiometers, variable resistors, and trimmers, with enhanced resolution, solid-state reliability, and superior temperature stability.
With digital rather than manual control, the AD5290 provides layout flexibility and allows closed-loop dynamic controllability.
The AD5290 is available in MSOP-10 package and has 10 kΩ, 50 kΩ, and 100 kΩ options. All parts are guaranteed to operate over the −40°C to +125°C extended automotive temperature range.

 

特徴

256 position
10 kΩ, 50 kΩ, 100 kΩ
+20 V to +30 V single-supply operation
±10 V to ±15 V dual-supply operation
3-wire SPI®-compatible serial interface
Low temperature coefficient 35 ppm/°C typical
THD 0.006% typical
Midscale preset
Compact MSOP-10 package
Automotive temperature range: −40°C to +125°C
iCMOS™1 process technology

 

アプリケーション

High voltage DAC
Programmable power supply
Programmable gain and offset adjustment
Programmable filters and delays
Actuator control
Audio volume control
Mechanical potentiometer replacement

 

仕様

1.Typical represents average reading at +25°C, VDD = +15 V, and VSS = −15 V.
2.Resistor position nonlinearity error R-INL is the deviation from an ideal value measured between the maximum resistance and the minimum resistance wiper positions. R-DNL measures the relative step change from an ideal value measured between successive tap positions. Parts are guaranteed monotonic.
3.All parts have a 35 ppm/°C temperature coefficient.
4.INL and DNL are measured at VW with the RDAC configured as a potentiometer divider similar to a voltage output DAC. VA = VDD and VB = 0 V. DNL specification limits of ±1 LSB maximum are guaranteed monotonic operating conditions.
5.Resistor Terminal A, Terminal B, and Terminal W have no limitations on polarity with respect to each other.
6.Guaranteed by design and not subject to production test.
7.PDISS is calculated from (IDD × VDD) + abs (ISS × VSS). CMOS logic-level inputs result in minimum power dissipation.
8.Bandwidth, noise, and settling times are dependent on the terminal resistance value chosen. The lowest R value results in the fastest settling time and highest bandwidth. The highest R value results in the minimum overall power consumption.
9.All dynamic characteristics use VDD = +15 V and VSS = −15 V.

 

動作理論

The AD5290 wiper switch is designed with the transmission gate CMOS topology and with the gate voltage derived from VDD. The wiper resistance, RW, is a function of VDD and temperature. Contrary to the temperature coefficient of the RAB, which is only 35 ppm/°C, the temperature coefficient of the wiper resistance is significantly higher because the wiper resistance doubles from 25°C to 125°C. As a result, the user must take into consideration the contribution of RW on the desirable resistance. On the other hand, the wiper resistance is insensitive to the tap point potential. As a result, RW remains relatively flat at a given VDD and temperature at various codes.
Assuming that an ideal 10 kΩ part is used, the wiper’s first connection starts at the B terminal for the programming code of 0x00 where SWB is closed. The minimum resistance between Terminal W and Terminal B is, therefore, generally 150 Ω. The second connection is the first tap point, which corresponds to 189 Ω (RWB = 1/256 × RAB + 3RW = 39 Ω + 150 Ω) for code 0x01, and so on. Each LSB data value increase moves the wiper up the resistor ladder until the last tap point is reached at 10,110 Ω.
In the zero-scale condition, a finite total wiper resistance of 150 Ω is present. Regardless of which setting the part is operating in, care should be taken to limit the current between the A terminal to B terminal, W terminal to A terminal, and W terminal to B terminal, to the maximum dc current of 5 mA or pulse current of 20 mA. Otherwise, degradation, or possible destruction of the internal switch contact, can occur.