Rainbow Electronics DS2890 - Manual (Page 28)

DS2890
28 of 28
AC ELECTRICAL CHARACTERISTICS - OVERDRIVE 1-WIRE SPEED
2.8V £ V
PUP
£ 6.0V, -40°C £ T
A
£ +85°C
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Recovery Time t
REC
1 µs
Reset High Time t
RSTH
48 µs
Reset Low Time t
RSTL
48 80 µs
Presence Detect High t
PDH
2 6 µs
Presence Detect Low t
PDL
8 24 µs
Notes:
1. The optimal sampling point for the master is as close as possible to the end time of the 2 ms t
RDV
period without exceeding t
RDV
. For the case of a Read-one time slot, this maximizes the amount of
time for the pull-up resistor to recover the line to a high level. For a Read-zero time slot it ensures
that a read will occur before the fastest 1-Wire device(s) release the line (t
RELEASE
= 0).
2. Read data setup time refers to the time the host must pull the 1-Wire bus low to read a bit. Data is
guaranteed to be valid within 1 µs of this falling edge.
3. An additional reset or communication sequence cannot begin until the reset high time (t
RSTH
) has
expired.
4. The reset low time (t
RSTL
) should be restricted to a maximum of 960 µs, to allow interrupt signaling,
otherwise, it could mask or conceal interrupt pulses.
CAPACITANCE TA = 25 °C
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
1-Wire Pin 800 pF 1
V
DD
Pin 10 pF
Resistor Terminals 10 pF
NOTE:
1. Capacitance on the 1-Wire pin could be 800 pF when power is first applied. If a 5 k W is used to pull
up the 1-Wire line to V
PUP
, the capacitance will not affect communications after a 5 ms charge time.