HYE25L256160AC Datasheet, PDF (13/55 Pages) Infineon Technologies AG – 256-Mbit Mobile-RAM

HYE25L256160AC
256-Mbit Mobile-RAM
Functional Description
3.3
Extended Mode Register
The Extended Mode Register controls functions beyond those controlled by the Mode Register. These additional
functions are unique to Mobile RAMs and includes a refresh period field (TCSR) for Temperature Compensated
Self Rrefresh and a Partial Array Self Refresh field (PASR).
The Extended Mode Register is programmed via the Mode Register Set command (with BA0 = 0 and BA1 = 1)
and retains the stored information until it is programmed again or the device looses power. The Extended mode
Register must be loaded when all banks are idle, and the controller must wait the specified time before initiating
any subsequent operation. Violating either these requirements result in unspecified operation. Unused bit A12 to
A5 have to be programmed to “0”.
3.3.1 Partial Array Self Refresh
The PASR field is a power saving feature specific to Mobile-RAMs and is used to specify whether only one quarter
or half of bank 0, one bank (bank 0), two banks (banks 0 + 1) or all four banks (default) of the SDRAM array are
enabled for Self Refresh. Disabled banks will not be refreshed in Self Refresh mode and written data will get lost
after a period defined by t_REF.
3.3.2 Temperature Compensated Self Refresh with On-Chip Temperature Sensor
DRAM devices store data as electrical charge in tiny capacitors that require a periodic refresh in order to retain
the stored information. This refresh requirment heavily depends on the die temperatur: high temperature
corresponds to short refresh period, and low temperature to long refresh period.
The Mobile-RAM is equipped with an on-chip temperature sensor which continuously monitors the current die
temperature and adjusts the refresh period in self refresh mode accordingly. By default the on-chip temperature
sensor is enabled (TCSR = 00, see Table "EMR" on Page 14); the other three TCSR settings use defined
temperature values to adjust the self refresh period to with the on-chip temperature sensor being disabled.
Data Sheet
13
V1.1, 2003-04-16