IS43/46DR16128

Integrated Silicon Solution, Inc. – www.issi.com –

3

Rev. B, 09/6/2012

Functional Description

Power-up and Initialization

DDR2 SDRAMs must be powered up and initialized in a predefined manner. Operational procedures other than those specified may

result in undefined operation.

Power-up and Initialization Sequence

The following sequence is required for Power-up and Initialization.

1. Either one of the following sequence is required for Power-up:

undefined.) The VDD voltage ramp time must be no greater than 200 ms from when VDD ramps from 300 mV to

VDD(Min); and during the VDD voltage ramp, |VDD-VDDQ| ≥ 0.3 V. Once the ramping of the supply voltages is

complete (when VDDQ crosses VDDQ(Min)), the supply voltage specifications provided in the table Recommended DC

Operating Conditions (SSTL_1.8), prevail.

− VDD, VDDL and VDDQ are driven from a single power converter output, AND

− VTT is limited to 0.95V max, AND

− VREF tracks VDDQ/2, VREF must be within ± 300mV with respect to VDDQ/2 during supply ramp time.

− VDDQ ≥ VREF must be met at all times

undefined, voltage levels at I/Os and outputs must be less than VDDQ during voltage ramp time to avoid DRAM latch-

up. During the ramping of the supply voltages, VDD ≥ VDDL ≥ VDDQ must be maintained and is applicable to both AC

and DC levels until the ramping of the supply voltages is complete, which is when VDDQ crosses VDDQ min. Once the

ramping of the supply voltages is complete, the supply voltage specifications provided in the table Recommended DC

Operating Conditions (SSTL-1.8), prevail.

− Apply VDD/VDDL before or at the same time as VDDQ.

− VDD/VDDL voltage ramp time must be no greater 200 ms from when VDD ramps from 300 mV to VDD(Min) .

− Apply VDDQ before or at the same time as VTT.

− The VDDQ voltage ramp time from when VDD(Min) is achieved on VDD to the VDDQ(Min) is achieved on VDDQ

must be no greater than 500 ms.

2. Start clock and maintain stable condition.

3. For the minimum of 200 µs after stable power (VDD, VDDL, VDDQ, VREF, and VTT values are in the range of the minimum and

maximum values specified in the table Recommended DC Operating Conditions (SSTL-1.8)) and stable clock (CK, CK#), then apply

NOP or Deselect and assert a logic HIGH to CKE.

4. Wait minimum of 400 ns then issue a precharge all command. During the 400 ns period, a NOP or Deselect command must be

issued to the DRAM.

5. Issue an EMRS command to EMR(2).

6. Issue an EMRS command to EMR(3).

7. Issue EMRS to enable DLL.

8. Issue a Mode Register Set command for DLL reset.

9. Issue a precharge all command.

10. Issue 2 or more auto-refresh commands.

11. Issue a MRS command with LOW to A8 to initialize device operation. (i.e. to program operating parameters without resetting

the DLL.)

12. Wait at least 200 clock cycles after step 8 and then execute OCD Calibration (Off Chip Driver impedance adjustment). If OCD

calibration is not used, EMRS Default command (A9=A8=A7=HIGH) followed by EMRS OCD Calibration Mode Exit command

(A9=A8=A7=LOW) must be issued with other operating parameters of EMR(1).

13. The DDR2 SDRAM is now ready for normal operation.

Note:

1.

To guarantee ODT off, VREF must be valid and a LOW level must be applied to the ODT pin.