Sierra Wireless WISMO218 - Manual (Page 65)

WA_DEV_W218_PTS_002 Rev 005 Page 65 of 109
Product Technical Specification &
Customer Design Guidelines
Application
The maximum peak current of the transistor/MOSFET is 100mA and the maximum average current is
40mA, while the peak current of the BUZZER pin should be less than 4mA. A diode against transient
peak voltage must be added as shown below.
BUZZER
C1 D1
VBATT
R1
WISMO218
34
R2
R3
T1
GND GND
Figure 28. Example of Buzzer Implementation
Where:

R1 must be chosen in order to limit the current at I
PEAK
max of 100mA and must be adjusted in
function of the frequency and the duty cycle used.

D1 = BAV70T-7 or BAS16 (for example)

T1 = FDN335N (for example)

R2 = 0

R3 = 1M

A low filter is recommended at low frequencies.