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ADM1060 データシート(PDF) 11 Page - Analog Devices |
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ADM1060 データシート(HTML) 11 Page - Analog Devices |
11 / 52 page ADM1060 Rev. B | Page 11 of 52 INPUTS POWERING THE ADM1060 The ADM1060 is powered from the highest voltage input on either the Positive Only supply inputs (VPn) or the High Volt- age supply input (VH). The same pins are used for supply fault detection (discussed below). A VDD arbitrator on the device chooses which supply to use. The arbitrator can be considered as diode OR’ing the positive supplies together (as shown in Figure 17).The diodes are supplemented with switches in a syn- chronous rectifier manner to minimize voltage loss. This loss can be reduced to ~0.2 V, resulting in the ability to power the ADM1060 from a supply as low as 3.0 V. Note that the supply on the VBn pins cannot be used to power the device, even if the input on these pins is positive. Also, the minimum supply of 3.0 V must appear on one of the VPn pins in order to correctly power up the ADM1060. A supply of no less than 4.5 V can be used on VH. This is because there is no synchronous rectifier circuit on the VH pin, resulting in a voltage drop of ~1.5 V across the diode of the VDD arbitrator. An external capacitor to GND is required to decouple the on-chip supply from noise. This capacitor should be connected to the VDDCAP pin, as shown in Figure 17. The capacitor has another use during “brown outs” (momentary loss of power). Under these conditions, where the input supply, VPn, dips transiently below VDD, the synchronous rectifier switch immediately turns off so that it does not pull VDD down. The VDD capacitor can then act as a reservoir to keep the chip active until the next highest supply takes over the powering of the device. A 1 µF capacitor is recommended for this function. A minimum capacitor value of 0.1 µF is required. Note that in the case where there are two or more supplies within 100 mV of each other, the supply that takes control of VDD first will keep control. For example, if VP1 is connected to a 3.3 V supply, VDD will power up to approximately 3.1 V through VP1. If VP2 is then connected to another 3.3 V supply, VP1 will still power the device, unless VP2 goes 100 mV higher than VP1. A second capacitor is required on the VCCP pin of the ADM1060. This capacitor is the reservoir capacitor for the central charge pump. Again, a 1 µF capacitor is recommended for this function. A minimum capacitor value of 0.1 µF is required. VH VP1 VP2 VP3 VP4 VDDCAP PIN OFF-CHIP DECOUPLING CAPACITOR ON-CHIP SUPPLY Figure 17. VDD Arbitrator Operation PROGRAMMABLE SUPPLY FAULT DETECTORS (SFDs) The ADM1060 has seven programmable supply fault detectors (SFDs): one high voltage detector (+2 V to +14.4 V), two bipolar detectors (+1 V to +6 V, −2 V to –6 V) and four positive only voltage detectors (+0.6 V to +6 V). Inputs are applied to these detectors via the VH (high voltage supply input), VBn (bipolar supply input), and VPn (positive only input) pins, respectively. The SFDs detect a fault condition on any of these input supplies. A fault is defined as undervoltage (where the supply drops below a preprogrammed level), overvoltage (where the supply rises above a preprogrammed level), or out-of-window (where the supply deviates outside either the programmed overvoltage or undervoltage threshold). Only one fault type can be selected at a time. An undervoltage (UV) fault is detected by comparing the input supply to a programmed reference (the undervoltage threshold). If the input voltage drops below the undervoltage threshold, the output of the comparator goes high, asserting a fault. The undervoltage threshold is programmed using an 8-bit DAC. On a given range, the UV threshold can be set with a resolution of Step Size = Threshold Range/255 An overvoltage (OV) fault is detected in exactly the same way, using a second comparator and DAC to program the reference. All thresholds are programmed using 8-bit registers, one regis- ter each for the seven UV thresholds and one each for the seven OV thresholds. The UV or OV threshold programmed by the user is given by B R T V N V V + × = 255 |
同様の部品番号 - ADM1060_15 |
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同様の説明 - ADM1060_15 |
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