Datasheet

Slave-to-Master
A read-data time slot begins like a write-one time slot. The
voltage on the data line must remain below V
ILMAX
until
the read low time t
RL
is expired. During the t
RL
window,
when responding with a 0, the DS1990A starts pulling
the data line low; its internal timing generator determines
when this pulldown ends and the voltage starts rising
again. When responding with a 1, the DS1990A does not
hold the data line low at all, and the voltage starts rising
as soon as t
RL
is over.
The sum of t
RL
+δ(risetime)ononesideandtheinternal
timing generator of the DS1990A on the other side define
the master sampling window (t
MSRMIN
to t
MSRMAX
) in
which the master must perform a read from the data line.
For most reliable communication, t
RL
should be as short
as permissible and the master should read close to but
no later than t
MSRMAX
. After reading from the data line,
the master must wait until t
SLOT
is expired. This guaran-
tees sufficient recovery time t
REC
for the DS1990A to get
ready for the next time slot.
PACKAGE TYPE PACKAGE CODE OUTLINE NO.
F3 iButton IB#3NB 21-0252
F5 iButton IB#5NB 21-0266
www.analog.com
Analog Devices │ 9
DS1990A Serial Number iButton
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.