Rainbow Electronics AT86RF231 - Manual (Page 110)

110
8111A–AVR–05/08
AT86RF231
9.4 Voltage Regulators (AVREG, DVREG)
The main features of the Voltage Regulator blocks are:
• Bandgap stabilized 1.8V supply for analog and digital domain
• Low dropout (LDO) voltage regulator
• Configurable for usage of external voltage regulator
9.4.1 Overview
The internal voltage regulators supply a stabilized voltage to the AT86RF231. The AVREG pro-
vides the regulated 1.8V supply voltage for the analog section and the DVREG supplies the 1.8V
supply voltage for the digital section.
A simplified schematic of the internal voltage regulator is shown in Figure 9-5 on page 110 .
Figure 9-5. Simplified Schematic of AVREG/DVREG
The voltage regulators require bypass capacitors for stable operation. The value of the bypass
capacitors determine the settling time of the voltage regulators. The bypass capacitors shall be
placed as close as possible to the pins and shall be connected to ground with the shortest possi-
ble traces.
9.4.2 Configuration
The voltage regulators can be configured by the register 0x10 (VREG_CTRL).
It is recommended to use the internal regulators, but it is also possible to supply the low voltage
domains by an external voltage supply. For this configuration, the internal regulators need to be
switched off by setting the register bits to the values AVREG_EXT = 1 and DVREG_EXT = 1. A
regulated external supply voltage of 1.8V needs to be connected to the pins 13, 14 (DVDD) and
pin 29 (AVDD). When turning on the external supply, ensure a sufficiently long stabilization time
before interacting with the AT86RF231.
9.4.3 Data Interpretation
The status bits AVDD_OK = 1 and DVDD_OK = 1 of register 0x10 (VREG_CTRL) indicate an
enabled and stable internal supply voltage. Reading value 0 indicates a disabled or internal sup-
ply voltage not settled to the final value.
Bandgap
voltage
reference
1.25V
AVDD,
DVDD
(D)EVDD