User's Manual

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USERS MANUAL
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Document number Revision
1/198 17-5/FCP 101 3317 Uen A
5.2 Status Interfaces
Status interfaces indicate or control status features of the modem.
• UVP
• OVP
• RI
• LED
• VREF
5.2.1 UVP
Function: Under voltage protection
Description: Status indicator to host of potential malfunction in Daughter Card
circuitry
Pin Number: 23
Signal Name: UVP (PD) [daughter card
⇒host]
If not used: Required
Details:
The Daughter Card has FET circuitry which uses 3V3 as a reference, driving an output to
the host indicating the voltage condition of the of VBAT (the modem supply voltage). A
resistive divider connected to VBATT presents a very low V
be
to the UVP transistor. This
presents a steady state low voltage output under normal VBAT conditions with external
pulldown circuitry. In the event of a short circuit or high current fault condition on the
Daughter Card, the voltage drop from the switching regulator will bias the UVP transistor
on and present a high output to the host equipment monitoring circuit.
The UVP signal should be pulled low by the application circuit for correct function.
Electrical Characteristics:
Parameter Condition Min Typ Max Unit
Normal 0.5 V
UVP output voltage
Fault 3.3 V
Table 5.2-1: UVP Electrical Characteristics