EM260-RTR Ember, EM260-RTR Datasheet - Page 20

• Manufacturer Part Number: EM260-RTR
• Description: IC ZIGBEE SYSTEM-ON-CHIP 40-QFN
• Manufacturer: Ember

Specifications of EM260-RTR

• Frequency: 2.4GHz
• Data Rate - Maximum: 250kbps
• Modulation Or Protocol: 802.15.4
• Applications: ZigBee™
• Power - Output: -32dBm ~ 3dBm
• Sensitivity: -97dBm
• Voltage - Supply: 2.1 V ~ 3.6 V
• Current - Receiving: 30mA
• Current - Transmitting: 34mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-QFN
• For Use With: 636-1009 - PROGRAMMER USB FLASH EM250/260
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Memory Size: -
• Other names: 636-1007-2; EM260-RTR

EM260
4.11 Random Number Generator
4.12 Watchdog Timer
20
120-1003-000D
Parameter
(max. bias)
Start-up time to stable clock
(optimum bias)
Current consumption
Current consumption
Current consumption
4.10.2 Internal RC Oscillator
The EM260 has a low-power, low-frequency RC oscillator that runs all the time. Its nominal frequency is
10kHz.
The RC oscillator has a coarse analog trim control, which is first adjusted to get the frequency as close to
10kHz as possible. This raw clock is used by the chip management block. It is also divided down to 1kHz using
a variable divider to allow software to accurately calibrate it. This calibrated clock is available to the sleep
timer.
Timekeeping accuracy depends on temperature fluctuations the chip is exposed to, power supply impedance,
and the calibration interval, but in general it will be better than 150ppm (including crystal error of 40ppm).
Table 13 lists the specifications of the RC oscillator.
Parameter
Frequency
Analog trim steps
Frequency variation with supply
The EM260 allows for the generation of random numbers by exposing a randomly generated bit from the RX
ADC. Analog noise current is passed through the RX path, sampled by the receive ADC, and stored in a regis-
ter. The value contained in this register could be used to seed a software-generated random number. The
EmberZNet stack utilizes these random numbers to seed the Random MAC Backoff and Encryption Key Genera-
tors.
The EM260 contains a watchdog timer clocked from the internal oscillator. If the timer reaches its time-out
value of approximately 2 seconds, it will generate a reset signal to the chip. The watchdog will generate a low
watermark interrupt in advance of actually resetting the chip. This low watermark interrupt occurs approxi-
mately 1.75 seconds after the timer has been restarted. This interrupt can be used to assist during application
debug.
The EM260 firmware will periodically restart the watchdog timer while the firmware is running normally. The
Host cannot effect or configure the watchdog timer.
Test Conditions
Good crystal: 20Ω ESR, 10pF load
Worst-case crystals (60Ω, 18pF or
100Ω, 10pF)
At maximum bias
Table 13. RC Oscillator Specifications
Test Conditions
For a voltage drop from 3.6V to 3.1V
or 2.6V to 2.1V
Min.
Min.
Typ.
0.2
Typ.
10
1
0.75
Max.
2
0.3
0.5
1
Max.
1.5
Unit
ms
mA
mA
mA
Unit
kHz
kHz
%