C8051F388-B Datasheet, PDF (70/285 Pages) Silicon Laboratories – Flash MCU Family

C8051F388/9/A/B
9. Voltage Regulators (REG0 and REG1)
C8051F388/9/A/B devices include two internal voltage regulators: one regulates a voltage source on
REGIN to 3.3 V (REG0), and the other regulates the internal core supply to 1.8 V from a V_DD supply of
1.8 to 3.6 V (REG1). When enabled, the REG0 output appears on the V_DD pin and can be used to power
external devices. REG0 can be enabled/disabled by software using bit REG0DIS in register REG01CN
(SFR Definition 9.1). REG1 has two power-saving modes built into the regulator to help reduce current
consumption in low-power applications. These modes are accessed through the REG01CN register. Elec-
trical characteristics for the on-chip regulators are specified in Table 5.5 on page 37.
9.1. Voltage Regulator (REG0)
See “4. Typical Connection Diagrams” for typical connection diagrams using the REG0 voltage regulator.
9.1.1. 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 5.5 for normal and low power mode supply current specifications. The REG0 mode
selection is controlled via the REG0MD bit in register REG01CN.
9.1.2. External Interrupt 2 (INT2)
On C8051F388/9/A/B devices, the VBSTAT bit (register REG01CN) indicates the current logic level of the
INT2 signal. If enabled, a INT2 interrupt will be generated when the INT2 signal has either a falling or rising
edge. The INT2 interrupt is edge-sensitive, and has no associated interrupt pending flag. See Table 5.3 for
INT2 input parameters.
9.2. Voltage Regulator (REG1)
Under default conditions, the internal REG1 regulator will remain on when the device enters STOP mode.
This allows any enabled reset source to generate a reset for the device and bring the device out of STOP
mode. For additional power savings, the STOPCF bit can be used to shut down the regulator and the inter-
nal power network of the device when the part enters STOP mode. When STOPCF is set to 1, the RST pin
and a full power cycle of the device are the only methods of generating a reset.
REG1 offers an additional low power mode intended for use when the device is in suspend mode. This low
power mode should not be used during normal operation or if the REG0 Voltage Regulator is disabled. See
Table 5.5 for normal and low power mode supply current specifications. The REG1 mode selection is con-
trolled via the REG1MD bit in register REG01CN.
Important Note: At least 12 clock instructions must occur after placing REG1 in low power mode before
the Internal High Frequency Oscillator is Suspended (OSCICN.5 = 1b).
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