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--- resources:technical-guides:best_engineering_practices_when_using_adxl_accelerometers [12 Feb 2021 20:26] – Pablo del Corro
+++ resources:technical-guides:best_engineering_practices_when_using_adxl_accelerometers [29 Mar 2021 17:24] – Pablo del Corro
@@ Line 21: / Line 21: @@
 === Power Cycling ===
-It is common in ULP applications to power cycle the accelerometer to reduce power consumption. When using this technique, please remember that it is highly recommend to always be started up the accelerometer from ground level (0 V) to ensure proper operation.
+It is common in ULP applications to power cycle the accelerometer to reduce power consumption. When using this technique, please remember that it is highly recommend to always start up the accelerometer from ground level (0 V) to ensure proper operation.
 If this is not possible, care must be taken regarding the following specifications:
-  * __**VS supply start-up threshold**__: During start-up or power cycling, the VS and VDDIO supplies must always be started up from below 200 mV. When the device is in operation, any time power is removed or falls below the accelerometer power supply lower range voltage, VS and VDDIO supplies must be discharged below 200 mV. **This specification is mandatory**.
+  * __**VS supply start-up threshold**__: During start-up or power cycling, the VS and VDDIO supplies must always be started up from below 100 mV. When the device is in operation, any time power is removed or falls below the accelerometer power supply lower range voltage, VS and VDDIO supplies must be discharged below 100 mV. **This specification is mandatory**.
-  * __**Hold time**__: VS and VDDIO supplies must be held below 200 mV for at least 100 ms before re-powering the part.
+  * __**Hold time**__: VS and VDDIO supplies must be held below 100 mV for at least 200 ms before re-powering the part.
-  * __**Rise time**__: For the worst case scenario, 200mV Vs starts up and 100ms hold time, VS and VDDIO supplies rise time must be linear and within 45 μs to reach the supply lower range voltage. For example, for the ADXL372, the power supply lower range voltage is 1.6V, thus the voltage supply should raise from 0V to 1.6V within 45μs.
+  * __**Rise time**__: For the worst case scenario (100mV Vs starts up and 200ms hold time) VS and VDDIO supplies rise time must be linear and within 250 μs to reach the supply lower range voltage. For example, for the ADXL372, the power supply lower range voltage is 1.6V, thus the voltage supply should raise from 0V to 1.6V within 250μs.
-Hold time and rise time specifications can vary. For example, if hold time is much longer than 100ms, the rise time criteria might be relaxed. The user should carefully select the start-up specifications that suits their application.
+<note>Fully discharging the power supply to the ground level allows a much more relaxed rise time, ≤600 µs, from 0 V to supply lower range voltage, for a 200 ms hold time.</note>
-<note>Fully discharging the power supply to ground level allows a much more relaxed rise time (≤ 500µs, from 0V to the power supply lower range voltage) and hold time as low as 10µs.</note>
 To enable supply discharge, it is recommended to power the device from a microcontroller general-purpose input/output (GPIO), connect a shutdown discharge switch to the supply, or use a voltage regulator with a shutdown discharge feature.

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