Propox MMstR75xFR, User Manual

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Voltage Regulator Voltage Regulator Voltage Regulator Voltage Regulator
Minimodule has built-in 3.3V voltage regulator. Thanks to it can be powered with 3.3V voltage
supplied to J2 3 pin (+3.3V) or with voltage between 3.8 – 9V, supplied to J2 1 pin (VCC).
When power is supplied to VCC pin, then 3.3V voltage is produced on the module by U3
regulator. In this case 3.3V voltage can be also used outside the module, if current draw will
not exceed 300mA.
Figure 5 3.3V Voltage Regulator
USB
USB USB
USB D+ Pull
D+ Pull D+ Pull
D+ Pull----Up circuit
Up circuit Up circuit
Up circuit
USB host recognize presence of device on the bus by sensing pull-up on D+ line.
MMstr75xFR has built-in pull-up circuit, shown on drawing below.
Figure 6 USB D+ Pull-Up circuit implementation
Pull-up is by default turned off by R4 resistor. Active reset signal or low level on UDP_PUP
(R5 mounted) line turns on pull-up, what is interpreted by USB host as connection of USB
device.