C8051F340 datasheet(73/288 Pages) SILABS

73 / 288 page

Rev. 1.0

C8051F340/1/2/3/4/5/6/7

8. Voltage Regulator (REG0)

C8051F340/1/2/3/4/5/6/7 devices include a voltage regulator (REG0). When enabled, the REG0 output

appears on the VDD pin and can be used to power external devices. REG0 can be enabled/disabled by

software using bit REGEN in register REG0CN. See Table 8.1 for REG0 electrical characteristics.

Note that the VBUS signal must be connected to the VBUS pin when using the device in a USB network.

The VBUS signal should only be connected to the REGIN pin when operating the device as a bus-powered

function. REG0 configuration options are shown in Figure 8.1–Figure 8.4.

8.1.

Regulator Mode Selection

REG0 offers a low power mode intended for use when the device is in suspend mode. In this low power

mode, the REG0 output remains as specified; however the REG0 dynamic performance (response time) is

degraded. See Table 8.1 for normal and low power mode supply current specifications. The REG0 mode

selection is controlled via the REGMOD bit in register REG0CN.

8.2.

VBUS Detection

When the USB Function Controller is used (see section

Section “16. Universal Serial Bus Controller

(USB0)” on page 167), the VBUS signal should be connected to the VBUS pin. The VBSTAT bit (register

REG0CN) indicates the current logic level of the VBUS signal. If enabled, a VBUS interrupt will be gener-

ated when the VBUS signal matches the polarity selected by the VBPOL bit in register REG0CN. The

VBUS interrupt is level-sensitive, and has no associated interrupt pending flag. The VBUS interrupt will be

active as long as the VBUS signal matches the polarity selected by VBPOL. See Table 8.1 for VBUS input

parameters.

Important Note: When USB is selected as a reset source, a system reset will be generated when the

VBUS signal matches the polarity selected by the VBPOL bit. See

Section “11. Reset Sources” on

page 105 for details on selecting USB as a reset source

Table 8.1. Voltage Regulator Electrical Specifications

–40 to +85 °C unless otherwise specified.

Parameter

Conditions

Min

Typ

Max

Units

Input Voltage Range1

2.7

5.25

Output Voltage (VDD)2

Output Current = 1 to 100 mA

3.0

3.3

3.6

Output Current2

100

VBUS Detection Input Threshold

1.0

1.8

4.0

Bias Current

Normal Mode (REGMOD = ‘0’)

Low Power Mode (REGMOD = ‘1’)

111

µA

Dropout Voltage (VDO)3

IDD = 1 mA

IDD = 100 mA

100

mV/mA

Notes:

1. Input range specified for regulation. When an external regulator is used, should be tied to

VDD.

2. Output current is total regulator output, including any current required by the C8051F34x.

3. The minimum input voltage is 2.70 V or VDD + VDO (max load), whichever is greater.

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