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ISL21400IU8Z-TK Fiches technique(PDF) 10 Page - Intersil Corporation |
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ISL21400IU8Z-TK Fiches technique(HTML) 10 Page - Intersil Corporation |
10 / 17 page 10 FN8091.0 December 14, 2006 Pin Descriptions VOUT Programmable voltage output pin. Absolute voltage is determined by device temperature and Equation 1. Drive capability is limited to ±500 μA output current and 5000pF output capacitance. A2, A1, A0 Hardware slave address pins that can be used to provide several ISL21400 with a unique physical address to allow for multiple devices off one I2C bus. GND This is the circuit ground pin. It is common for the VOUT and control signal inputs. SDA Serial Data Input/Output. Bidirectional pin used for serial data transfer. As an output, it is open drain and may be wire-ored with any number of open drain or open collector outputs. A pullup resistor is required and the value is dependent on the speed of the serial data bus and the number of outputs tied together. SCL Serial Clock Input. Accepts a clock signal for clocking serial data into and out of the device. The SCL line requires a pullup resistor whose value is dependent on the speed of the serial clock bus and the number of inputs tied together. VCC Positive Power Supply. Connect to a voltage supply in the range of 2.7V < VCC<5.5V, with minimum noise and ripple. For best performance, bypass with a 0.1µF capacitor to ground. If the AV gain is set to 4 and VOUT approaches 5.0V, then VCC must be set to >5.2V for best output performance. Functional Description Functional Overview Refer to the Functional Block Diagram on page 2. The ISL21400 provides a programmable output voltage which combines both a temperature independent term and a temperature dependent term. The temperature independent term uses a bandgap voltage reference, and the temperature dependent term uses a Proportional To Absolute Temperature (PTAT) reference, or Temperature Sensor. Each voltage source is scalable using two DACs via the I2C serial bus. The resulting output voltage can vary from 0V to over 5V and has a variable, programmable Temperature Slope (TS). Reference Sections Referring to the Block Diagram on page 2, the VREF and Temperature Sense (VTS) outputs are summed together (Σ) and then passed through the output gain stage (A). The voltage output is programmable and is determined by the following equation: where •AV = 1, 2, 4 •VREF = 1.200 (not temperature dependent) •0 ≤ n ≤ 255 (setting contained in Register 0, V REF) •VTS = K(T-T0) •K = dVTS/ dT = -2.1mV/C • T = device temperature •T0 = +25°C •0 ≤ m ≤ 255 (setting contained in Register 1, TS) See the Applications Information for ways to use Equation 1 and methods for output voltage calculations. DACs Section The ISL21400 contains two 8-bit DACs whose registers can be programmed via the I2C serial bus. The DAC registers are non-volatile such that the values are restored during the VCC power-up cycle of the device. One DAC (VREF)is dedicated to scale the bandgap voltage reference (Temperature invariant) and the other DAC (VTS) is dedicated to scale the Temperature Sensor. Both of these DACs can determine the output voltage as defined by Equation 1 (See Register Information). Output Gain Amplifier Section The ISL21400 contains an output gain amplifier (A) that is programmed via the I2C serial bus. The gain amplifier is the last stage before the output and therefore controls the overall gain for the device. The gain can be programmed for 1x, 2x, or 4x amplification. This gain factor is used to program the output voltage as determined by Equation 1 (See Register Description). There are 5 registers in the ISL21400 device, all nonvolatile (see Table 2). All registers are accessible for reading or writing through the I2C serial bus. V OUT A V V REF n 255 ---------- • V TS 2m • () 255 – 255 -------------------------------- + ⎩⎭ ⎨⎬ ⎧⎫ • = (EQ. 1) ISL21400 |
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