Sierra Wireless AIRPRIME WISMO218 - Manual (Page 72)

WA_DEV_W218_PTS_002 Rev 006 April 29, 2010 72
Product Technical Specification &
Customer Design Guidelines Interfaces
3.17. TX_CTRL Signal for TX Burst Indication
3.17.1. Features
The TX_CTRL signal is a 2.8V indication signal for TX Burst with a 100K  pull-up resistor
implemented inside the AirPrime WISMO218 embedded module.
Table 33: TX_CTRL Status
AirPrime WISMO218 State TX_CTRL Status
During TX burst Low
No TX High
During TX burst, there will be higher current drain from the VBATT power supply which causes a
voltage drop. This voltage drop from VBATT is a good indication of a high current drain situation
during TX burst.
The blinking frequency is about 216Hz.
The output logic low duration, T
duration
, depends on the number of TX slots and is computed as follows:
T
duration
= T
advance
+ (0.577ms x number of TX slots) + T
delay
.
Figure 36. TX_CTRL State During TX Burst
Table 34: Electrical Characteristics of the Signal
Parameter Condition Minimum Typ. Maximum Unit
V
OH
2.6 - 2.95 V
V
OL
- - 0.4 V
T
advance
@500mA - 18 - µs
@1A - 27 - µs
T
delay
- 11 - µs