4.1. Electrical Characteristics

Description	Symbol	Value		Unit
		Min.	Max.
Input voltage power supply	Vcc	2	3.6	V
Average current consumption @3Vdc	Icc	-	-	-
Idle mode		-	TBC	uA
CW @14dBm		-	42	mA
Maximum Radio power conducted	Prf		15	dBm
Operational temperature	T(°C)	-20	60	°C
Digital Input Level High (Vdd 3V)	VIH	2.1	3	Vcc
Digital Input Level Low (Vdd 3V)	VIL	0.0	0.9	Vcc

[!WARNING] Please be aware that power supply impedance have to be as low as possible in order to ensure reliable transmission & modulation. If the internal serial resistance of the battery used to power your device is not < few Ohms, please consider voltage regulators to stabilize power supply during the radio burst.

4.2. Schematic explanation

4.2.1 Schematic

Recommandation from Holtek :  Holtek suggested adding a resistor to RFOUT, it will help to adjust if the radiation leaks.

4.2.2. Matching & Filter

4.2.2.1. RC1 and RC2 Matching filter configuration

The following components need to be equipped : L2, L3, L4, L5, C10, C11, C12 and C13

[!WARNING]
The shielding is mandatory for RC2 configuration

4.2.2.2. RC3 and RC4 Matching filter configuration

The following components need to be equipped : R2 and R6 = 0ohm, FL1 SAW filter ref : B39921B3419U41, C10 = 1pF and L2 = 0ohm

[!WARNING]
L2, L3, L4, L5, C11, C12 and C13 are not equipped

4.2.3. Crystal selection

Crystal selection is a critical part of the design for any Radio system. here is an example of crystal parameters chosen in this ref design.

[!WARNING]
The final design have to be compliant with Sigfox specification : see REF 4

4.2.3.1. Crystal Specifications

Description	Symbol	Value		Unit
		Min.	Max.
Frequency	F	16	16	MHz
Load Capacitor	Cl	12	20	pF
Frequency aging			+/-1	ppm/year
Frequency tolerance @+25°C	Ftol	-	+/-10	ppm
Frequency temperature tolerance	Ftemp	-	+/-10	ppm
ESR	ESR	-	40	Ω

The reference that was used in the ref design is : ECS-160-16-33B-CKM-TR but we have also validated ref. : ECS-160-CDX-2469 and FTR5244-A0/16.000MHz Rakon

4.2.4. Connectors

4.2.4.1. Programming connector (J3)

The programming connector is directly compatible with the Holtek 8-bit MCU debug adapter e-link

You can buy the e-link here : were

Signal Name	I/O	J3 Pin Number	Descriptions
VCC	I	1	Power supply
NC		2
PA2-OCDSCK	I	3	Serial programming clock
NC		4
PA0-OCDSDA	I/O	5	Serial programming data
GND	I	6	Ground

4.2.4.2. Battery connector (J1)

This connector has been placed in order to supply the Ref design by a Power supply, or battery.

Signal Name	I/O	J 1 Pin Number	Descriptions
VCC	I	1	Power supply (2 to 3.6V)
GND	I	2	GROUND

4.2.4.3. Sensor connector (J4)

This connector has been placed in order to allow some sensors connection. (no implementation in the firmware provided)

Signal Name	I/O	J4 Pin Number	Descriptions
VCC	I	1	Power supply
PA3	I/O	2	I/O for sensor
PA4	I/O	3	I/O for sensor
PA5	I/O	4	I/O for sensor
GND	I	5	Ground