Datasheet

t
LZ(DQS)
, t
LZ(DQ)
, t
HZ(DQS)
, t
HZ(DQ)
Calculation
t
HZ
and t
LZ
transitions occur in the same time window as valid data transitions. These parameters are referenced
to a specific voltage level that specifies when the device output is no longer driving t
HZ(DQS)
and t
HZ(DQ)
, or begins
driving t
LZ(DQS)
, t
LZ(DQ)
.
t
LZ
shows a method to calculate the point when the device is no longer driving t
HZ(DQS)
and t
HZ(DQ)
, or begins
driving t
LZ(DQS)
, t
LZ(DQ)
, by measuring the signal at two different voltages. The actual voltage measurement points
are not critical as long as the calculation is consistent. The parameters t
LZ(DQS)
, t
LZ(DQ)
, t
HZ(DQS)
, and t
HZ(DQ)
are
defined as single ended.
Table 37. Reference Voltage for tLZ(DQ), tHZ(DQ) Timing Measurements
Symbol
Parameter
Vsw1
Vsw2
Unit
t
LZ(DQ)
DQ low-impedance time from CK, CK#
(0.70 - 0.04) x V
DDQ
(0.70 + 0.04) x V
DDQ
V
t
HZ(DQ)
DQ high impedance time from CK, CK#
(0.70 - 0.04) x V
DDQ
(0.70 + 0.04) x V
DDQ
V
Table 38. Reference Voltage for tLZ(DQS#), tHZ(DQS) Timing Measurements
Symbol
Parameter
Vsw1
Vsw2
Unit
t
LZ(DQS#)
DQS# low-impedance time from CK, CK#
(0.70 - 0.04) x V
DDQ
(0.70 + 0.04) x V
DDQ
V
t
HZ(DQS)
DQS high impedance time from CK, CK#
(0.70 - 0.04) x V
DDQ
(0.70 + 0.04) x V
DDQ
V
Table 39. Reference Voltage for tRPRE Timing Measurements
Symbol
Parameter
Vsw1
Vsw2
Unit
t
RPRE
DQS, DQS# differential Read Preamble
(0.30 - 0.04) x V
DDQ
(0.30 + 0.04) x V
DDQ
V
Table 40. Reference Voltage for tRPST Timing Measurements
Symbol
Parameter
Vsw1
Vsw2
Unit
t
RPST
DQS, DQS# differential Read Postamble
(-0.30 - 0.04) x V
DDQ
(-0.30 + 0.04) x V
DDQ
V
AS4C256M16D4
Confidential
- 93 of 201 -
Rev.1.0 Aug.2019