UPSD3212A Datasheet, PDF (86/163 Pages) STMicroelectronics – Flash Programmable System Devices with 8032 MCU with USB and Programmable Logic

uPSD3212A, uPSD3212C, uPSD3212CV
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 1.5kΩ pull-up resistor to a
3.3V supply. An approved alternative method is a
7.5kΩ pull-up to the USB V_CC supply. This alterna-
tive is defined for low-speed devices with an inte-
grated cable. The chip is specified for the 7.5kΩ
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.
Figure 42. USB Data Signal Timing and Voltage Levels
V_OH
VCR
V_OL
t_R
D+
10%
D-
90%
t_F
90%
10%
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Figure 43. Receiver Jitter Tolerance
T_PERIOD
Differential
Data Lines
T_JR
T_JR1
T_JR2
Consecutive
Transitions
N*T_PERIOD+T_JR1
Paired
Transitions
N*T_PERIOD+T_JR2
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