UPSD3254 STMICROELECTRONICS [STMicroelectronics], UPSD3254 Datasheet - Page 98

• Manufacturer Part Number: UPSD3254
• Description: Flash Programmable System Devices with 8032 Microcontroller Core
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

UPSD3254A, UPSD3254BV, UPSD3253B, UPSD3253BV
External USB Pull-Up Resistor
The USB system specifies a pull-up resistor on the
D- pin for low-speed peripherals. The USB
Spec 1.1 describes a 1.5k
3.3V supply. An approved alternative method is a
7.5k pull-up to the USB V
Figure 46. USB Data Signal Timing and Voltage Levels
Figure 47. Receiver Jitter Tolerance
98/175
Differential
Data Lines
T
PERIOD
VCR
V
V
OH
OL
D+
D-
CC
10%
pull-up resistor to a
supply. This alterna-
N*T
T
Consecutive
JR
Transitions
t
R
PERIOD
90%
+T
JR1
N*T
Transitions
PERIOD
Paired
+T
tive is defined for low-speed devices with an inte-
grated cable. The chip is specified for the 7.5k
pull-up. This eliminates the need for an external
3.3V regulator, or for a pin dedicated to providing
a 3.3V output from the chip.
JR2
90%
T
JR1
t
F
10%
T
JR2
AI06631
AI06632