Datasheet

CP2102/9

Rev. 1.8 19

10. Voltage Regulator

The CP2102/9 includes an on-chip 5 to 3 V voltage regulator. This allows the CP2102/9 to be configured as either

a USB bus-powered device or a USB self-powered device. These configurations are shown in Figure 6, Figure 7,

Figure 8, Figure 9, and Figure 10. When enabled, the 3 V voltage regulator output appears on the V

pin and can

be used to power external 3 V devices. See Table 6 for the voltage regulator electrical characteristics.

Alternatively, if 3 V power is supplied to the V

pin, the CP2102/9 can function as a USB self-powered device with

the voltage regulator disabled. For this configuration, it is recommended that the REGIN input be tied to the 3 V net

to disable the voltage regulator. In addition, if VDD or REGIN may be unpowered while VBUS is 5 V, a resistor

divider (or functionally-equivalent circuit) shown in Note 1 of Figure 8 and Figure 10 is required to meet the

absolute maximum voltage on VBUS specification in Table 2.

The USB max power and power attributes descriptor must match the device power usage and configuration. See

“AN721: CP210x/CP211x Device Customization Guide” for information on how to customize USB descriptors for

the CP2102/9.

Note: It is recommended to connect additional decoupling capacitance (e.g., 0.1 µF in parallel with 1.0 µF) to the REGIN input.

Figure 6. Configuration 1: USB Bus-Powered

Voltage Regulator (REG0)5 V In

3 V Out

VBUS Sense

REGIN

VBUS

From VBUS

To 3 V

Power Net

Device

Power Net

CP2102/9

1.0 F 0.1 F

4.7 F

0.1 F