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X40035VB Datasheet(PDF) 8 Page - Intersil Corporation |
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X40035VB Datasheet(HTML) 8 Page - Intersil Corporation |
8 / 23 page 8 FN8114.2 August 25, 2008 FIGURE 3. VTRIPX SET/RESET CONDITIONS Watchdog Timer The Watchdog Timer circuit monitors the microprocessor activity by monitoring the SDA and SCL pins. A standard read or write sequence to any slave address byte restarts the watchdog timer and prevents the WDO signal from going active. A minimum sequence to reset the watchdog timer requires four microprocessor instructions namely, a Start, Clock Low, Clock High and Stop. The state of two nonvolatile control bits in the Status Register determine the watchdog timer period. The microprocessor can change these watchdog bits by writing to the X40030, X40031, X40034, X40035 control register (also refer to page 21). FIGURE 4. WATCHDOG RESTART V1, V2 and V3 Threshold Program Procedure (Optional) The X40030 is shipped with standard V1, V2 and V3 threshold (VTRIP1, VTRIP2, VTRIP3) voltages. These values will not change over normal operating and storage conditions. However, in applications where the standard thresholds are not exactly right, or if higher precision is needed in the threshold value, the X40030, X40031, X40034, X40035 trip points may be adjusted. The procedure is described in the following and uses the application of a high voltage control signal. Setting a VTRIPx Voltage (x = 1, 2, 3) There are two procedures used to set the threshold voltages (VTRIPx), depending upon if the threshold voltage to be stored is higher or lower than the present value. For example, if the present VTRIPx is 2.9V and the new VTRIPx is 3.2V, the new voltage can be stored directly into the VTRIPx cell. If however, the new setting is to be lower than the present setting, then it is necessary to “reset” the VTRIPx voltage before setting the new value. Setting a Higher VTRIPx Voltage (x = 1, 2, 3) To set a VTRIPx threshold to a new voltage which is higher than the present threshold, the user must apply the desired VTRIPx threshold voltage to the corresponding input pin (Vcc(V1MON), V2MON or V3MON). Then, a programming voltage (Vp) must be applied to the WDO pin before a START condition is set up on SDA. Next, issue on the SDA pin the Slave Address A0h, followed by the Byte Address 01h for VTRIP1, 09h for VTRIP2, and 0Dh for VTRIP3, and a 00h Data Byte in order to program VTRIPx. The STOP bit following a valid write operation initiates the programming sequence. Pin WDO must then be brought LOW to complete the operation. To check if the VTRIPX has been set, set VXMON to a value slightly greater than VTRIPX (that was previously set). Slowly ramp down VXMON and observe when the corresponding outputs (LOWLINE, V2FAIL and V3FAIL) switch. The voltage at which this occurs is the VTRIPX (actual). CASE A If the desired VTRIPX is greater than the VTRIPX (actual), then add the difference between VTRIPX (desired) – VTRIPX (actual) to the original VTRIPX desired. This is your new VTRIPX that should be applied to VXMON and the whole sequence should be repeated again (see Figure 5). CASE B If the VTRIPX (actual), is higher than the VTRIPX (desired), perform the reset sequence as described in the next section. VCC/V2MON/V3MON VTRIPX VP tWC A0h 0 7 70 7 0 SCL WDO SDA (X = 1, 2, 3) 00h SCL SDA 0.6µs 1.3µs WDT RESET START STOP X40030, X40031, X40034, X40035 |
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