SSTUB32868 Datasheet, PDF (11/30 Pages) NXP Semiconductors – 1.8 V 28-bit 1 : 2 configurable registered buffer with parity for DDR2-800 RDIMM applications

NXP Semiconductors
SSTUB32868
1.8 V DDR2-800 configurable registered buffer with parity
Table 5. Parity and standby function table
Inputs
RESET
DCS0^[1]
DCS1^[1]
CK
CK
H
L
X
↑
↓
H
L
X
↑
↓
H
L
X
↑
↓
H
L
X
↑
↓
H
X
L
↑
↓
H
X
L
↑
↓
H
X
L
↑
↓
H
X
L
↑
↓
H
H
H
↑
↓
H
X
X
L or H
L or H
L
X or floating X or floating X or floating X or floating
∑ of inputs = H
(D1 to D28)
even
odd
even
odd
even
odd
even
odd
X
X
X
PAR_IN^[2]
L
L
H
H
L
L
H
H
X
X
X or floating
Output
QERR^[3][4]
H
L
L
H
H
L
L
H
QERR_0[5]
QERR₀
H
[1] DCS2 and DCS3 operate identically to DCS0 and DCS1 with regard to the parity function.
[2] PAR_IN arrives one clock cycle after the data to which it applies.
[3] This transition assumes QERR is HIGH at the crossing of CK going HIGH and CK going LOW. If QERR is LOW, it stays latched LOW for
two clock cycles or until RESET is driven LOW.
[4] QERR₀ is the previous state of output QERR.
[5] If DCS0, DCS1, DCS2, DCS3 and CSGEN are driven HIGH, the device is placed in Low-Power Mode (LPM). If a parity error occurs on
the clock cycle before the device enters the LPM and the QERR output is driven LOW, it stays latched LOW for the LPM duration plus
two clock cycles or until RESET is driven LOW.
7.2 Functional information
The SSTUB32868 is a 28-bit 1 : 2 configurable registered buffer designed for 1.7 V to
1.9 V V_DD operation.
All inputs are compatible with the JEDEC standard for SSTL_18, except the chip-select
gate-enable (CSGEN), control (C), and reset (RESET) inputs, which are LVCMOS. All
outputs are edge-controlled circuits optimized for unterminated DIMM loads, and meet
SSTL_18 specifications, except the open-drain error (QERR) output.
The device supports low-power standby operation. When 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 except QERR. The LVCMOS RESET and C inputs always
must 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 LOW state during power-up.
In the DDR2 RDIMM application, RESET is specified to be completely asynchronous with
respect to CK and CK. Therefore, no timing relationship can be ensured between the two.
When entering reset, the register will be cleared and the data 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
SSTUB32868_4
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 04 — 22 April 2010
© NXP B.V. 2010. All rights reserved.
11 of 30