Reproduction forbidden without Fibocom Wireless Inc. written authorization - All rights
reserved.
FIBOCOM SC138-
NA
Series Hardware Guide
65/88
For the ESD protection device of the earphone interface, use the bidirectional TVS tubes.
3.19.5
Speaker Circuit Design
M odule
S P K R _D R V _N
S P K R _D R V _P
39
pF
39
pF
Figure 3-23 Speaker circuit design
3.20
Forced Downloading Interface Design
SC138 series modules provide FORCE_USB_BOOT pins as emergency downloading interfaces. Short-
circuit the USB_FORCE_BOOT and VREG_L9_1P8 pins when starting up, and the module can enter
the emergency downloading mode. It is the final processing method when the product cannot start up or
run normally due to faults. Reserve this pin to facilitate the subsequent software upgrade and
commissioning of the product. The reference circuit is shown in the following figure:
M odule
FORCE_BOOT
S 1
VREG_L9_1P8
1K
Figure 3-24 Forced downloading interface design
