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AS4C8M32MD2A-25BCN Datasheet(PDF) 28 Page - Alliance Semiconductor Corporation |
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AS4C8M32MD2A-25BCN Datasheet(HTML) 28 Page - Alliance Semiconductor Corporation |
28 / 75 page Temperature Sensor Mobile LPDDR2 devices feature a temperature sensor whose status can be read from MR4. This sensor can be used to determine an appropriate refresh rate, determine whether AC timing derating is required in the extended temperature range, and/or monitor the operating temperature. Either the temperature sensor or the device operating temperature can be used to determine whether operating temperature requirements are being met (see Operating Temperature Range table). Temperature sensor data can be read from MR4 using the mode register read protocol. Upon exiting self-refresh or power-down, the device temperature status bits will be no older than tTSI. When using the temperature sensor, the actual device case temperature may be higher than the operating temperature specification that applies for the standard or extended temperature ranges. For example, TCASE could be above 85°C when MR4[2:0] equals 011b. To ensure proper operation using the temperature sensor, applications must accommodate the parameters in the temperature sensor definitions table. Table 25. Temperature Sensor Definitions and Operating Conditions Parameter Description Symbol Min/Max Value Unit System temperature gradient Maximum temperature gradient experienced by the memory device at the temperature of interest over a range of 2°C TempGradient Max System-dependent °C/s MR4 READ interval Time period between MR4 READs from the system ReadInterval Max System-dependent ms Temperature sensor interval Maximum delay between internal updates of MR4 tTSI Max 32 ms System response delay Maximum response time from an MR4 READ to the system response SysRespDelay Max System-dependent ms Device temperature margin Margin above maximum temperature to support controller response TempMargin Max 2 °C Moblie LPDDR2 devices accommodate the temperature margin between the point at which the device temperature enters the extended temperature range and the point at which the controller reconfigures the system accordingly. To determine the required MR4 polling frequency, the system must use the maximum TempGradient and the maximum response time of the system according to the following equation: TempGradient × (ReadInterval + tTSI + SysRespDelay) ≦ 2°C For example, if TempGradient is 10°C/s and the SysRespDelay is 1ms: 10°C/s * (ReadInterval + 32ms + 1ms) ≦ 2°C In this case, ReadInterval must not exceed 167ms DQ Calibration Mobile LPDDR2 devices feature a DQ Calibration function that outputs one of two predefined system timing calibration patterns. A Mode Register Read to MR32 (Pattern “A”) or MR40 (Pattern “B”) will return the specified pattern on DQ[0], DQ[8], DQ[16], and DQ[24] for x32 devices. For x32 devices, DQ[7:1], DQ[15:9], DQ[23:17], and DQ[31:25] may optionally drive the same information as DQ[0] or may drive 0b during the MRR burst. For LPDDR2 devices, MRR DQ Calibration commands may only occur in the idle state. Table 26. Data Calibration Pattern Description Pattern MR# Bit Time 0 Bit Time 1 Bit Time 2 Bit Time 3 Pattern A MR32 1 0 1 0 Pattern B MR40 0 0 1 1 AS4C8M32MD2A-25BCN Confidential - 28 of 75 - Rev.1.0 Jun. 2018 |
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