Datasheet

Electrical Specifications
USB Low-Speed Source Electrical Characteristics
MC68HC908JB8•MC68HC08JB8•MC68HC08JT8 — Rev. 2.3 Technical Data
Freescale Semiconductor Electrical Specifications 259
18.10 USB Low-Speed Source Electrical Characteristics
Characteristic
(1)
NOTES:
1. All voltages are measured from local ground, unless otherwise specified. All timings use a capacitive load of 50 pF, unless
otherwise specified. Low-speed timings have a 1.5kΩ pullup to 2.8 V on the D– data line.
Symbol Conditions Min Typ Max Unit
Internal operating frequency
f
OP
——3—MHz
Transition time
(2)
Rise time
Fall time
2. Transition times are measured from 10% to 90% of the data signal. The rising and falling edges should be smoothly tran-
sitioning (monotonic). Capacitive loading includes 50 pF of tester capacitance.
t
R
t
F
C
L
= 200 pF
C
L
= 600pF
C
L
= 200 pF
C
L
= 600pF
75
75
—
—
300
300
ns
Rise/Fall time matching
t
RFM
t
R
/t
F
80 — 120 %
Low speed data rate
t
DRATE
1.5 Mbs ± 1.5%
1.4775
676.8
1.500
666.0
1.5225
656.8
Mbs
ns
Source differential driver jitter
To next transition
For paired transitions
t
DDJ1
t
DDJ2
C
L
= 600 pF
Measured at
crossover point
–25
–10
—
—
25
10
ns
Receiver data jitter tolerance
To next transition
For paired transitions
t
DJR1
t
DJR2
C
L
= 600 pF
Measured at
crossover point
–75
–45
—
—
75
45
ns
Source SEO interval of EOP
t
LEOPT
Measured at
crossover point
1.25 — 1.50 µs
Source jitter for differential transition
to SE0 transition
(3)
3. The two transitions are a (nominal) bit time apart.
Measured at
crossover point
667 ns
Receiver SEO interval of EOP
Must reject as EOP
Must accept
t
LEOPR1
t
LEOPR2
Measured at
crossover point
210
670
—
—
—
—
ns
Width of SEO interval during
differential transition
t
LST
Measured at
crossover point
——210ns