IDT74SSTUBF32866B

This 25-bit 1:1 or 14-bit 1:2 configurable registered buffer is designed for 1.7-V to 1.9-V V_DD operation.

All clock and data inputs are compatible with the JEDEC standard for SSTL_18. The control inputs are LVCMOS. All outputs are 1.8-V CMOS drivers that have been optimized to drive the DDR-II DIMM load. IDT74SSTUBF32866B operates from a differential clock (CLK and CLK). Data are registered at the crossing of CLK going high, and CLK
going low.

The C0 input controls the pinout configuration of the 1:2 pinout from A configuration (when low) to B configuration (when high). The C1 input controls the pinout configuration from 25-bit 1:1 (when low) to 14-bit 1:2 (when high).

A - Pair Configuration (C01 = 0, C11 = 1 and C02 = 0, C12 = 1)
Parity that arrives one cycle after the data input to which it applies is checked on the PAR_IN of the first register. The
second register produces to PPO and QERR signals. The QERR of the first register is left floating. The valid error
information is latched on the QERR output of the second register. If an error occurs QERR is latched low for two
cycles or until RESET is low.

B - Single Configuration (C0 = 0, C1 = 0)
The device supports low-power standby operation. When the RESET input (RESET) is low, the differential input
receivers are disabled, and undriven (floating) data, clock and reference voltage (VREF) inputs are allowed. In
addition, when RESET is low all registers are reset, and all outputs are forced low. The LVCMOS RESET and Cn inputs
must always be held at a valid logic high or low level. To ensure defined outputs from the register before a stable
clock has been supplied, RESET must be held in the lowstate during power up.

In the DDR-II RDIMM application, RESET is specified to be completely asynchronous with respect to CLK and CLK. Therefore, no timing relationship can be guaranteed between the two. When entering reset, the register will be
cleared and the outputs will be driven low quickly, relative to the time to disable the differential input receivers. However, when coming out of reset, the register will become active quickly, relative to the time to enable the differential input receivers. As long as the data inputs are low, and the clock is stable during the time from the low-to-high transition of RESET until the input receivers are fully enabled, the design of the IDT74SSTUBF32866B must ensure that the outputs will remain low, thus ensuring no glitches on the output.

The device monitors both DCS and CSR inputs and will gate the Qn outputs from changing states when both DCS and CSR inputs are high. If either DCS and CSR input is low, the Qn outputs will function normally. The RESET input has priority over the DCS and CSR control and will force the outputs low. If the DCS-control functionality is not desired, then the CSR input can be hardwired to ground, in which case, the setup-time requirement for DCS would be the same as for the other D data inputs. Package options include 96-ball LFBGA (MO-205CC).