Rainbow Electronics AT86RF230 - Manual (Page 21)

21
AT86RF230
5131A-ZIGB-06/14/06
range from 400 nF to 10 µF. A higher capacitor value provides better voltage stability, but increases the voltage
regulator settling time.
Bandgap
voltage
reference
1.25V
VDEC
VDD
VREG_TRIM[1:0]
Figure 6-1. Simplified Schematic of VREG
The voltage regulators can be configured using the register 0x10 (VREG_CTRL). The read-only bit values
AVDD_OK = 1 and DVDD_OK = 1 indicate a stable, regulated supply voltage.
It is possible to use external voltage regulators instead of the internal regulators. For this special application 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 VDEC1 and
VDEC2. When turning on the external supply, ensure a sufficiently long stabilization time before interacting with the
AT86RF230.
6.5. Battery Monitor
The battery monitor (BATMON) detects and signals a low battery or supply voltage. This is done by comparing the
current voltage on the VDD pins with a programmable internal threshold voltage. Figure 6-2 shows the simplified
schematic of the BATMON with the most important input and output signals.
BATMON_HR
BATMON_VTH
4
VDD
Threshold
Voltage
BATMON_OK
„1“
BATMON_IRQ
For input-to-output mapping
see control register
0x11 (BATMON)
DAC
+
-
D
Q
clear
Figure 6-2. Simplified Schematic of BATMON