Nokia RH-6 Series Baseband Description & Troubleshooting page 40

RH-6
6 - BB Description & Troubleshooting
FBUS is used as additional communication channel from phone to accessory and vice
versa. There is two types of accessories which it uses:
1. Nokia Serial Bus Accessory, AT mode
2. Fbus Phonet mode accessory
From HW-point of view, this does not make any difference.
Signal Parameter
FBUS_RX V
IH
V
IL
FBUS_TX V
OH
V
OL
VOUT (Accessory Voltage Regulator)
DCT4 chip set does not provide and power supply for accessories. To enable this an exter-
nal LDO regulator is needed. This regulator is called "Accessory Regulator".
The regulator input is connected directly to battery voltage VBAT and the output to VOUT
pin at system connector. The regulator is controlled by the GENIO(0) line of UPP. With
this signal the regulator can be switched on and off.
The regulator can be supply up to150 mA. (note: this exceeds the Pop-port minimum
requirement.)
UPP
Signal
Vout
GenIO(0)
The pull-down resistor on the enable input of the regulator is needed because in the
switch-off mode of the phone, the output level of the Genio(0) is not defined. Without
this resistor's the output of the regulator can be floating.
Page 40
Company Confidential
Table 19: FBUS interface
Min Typ
1.95 2.78
0 0.2
1.95 2.78
0 0.2
VBAT
Voltage
regulator
GenIO(0)
En
LP3985
Figure 22: Accessory Power Supply Diagram
Table 20: Accessories Power Supply
Min Nom Max
2.63 2.80 2.88
2,56
1.4 1.88 0.6
0.6
© 2003 Nokia Corporation.
CCS Technical Documentation
Max Unit
3.0 Volt
0.83
2.83
0.83
Tomahawk
bottom connector
VOUT
0.9R
DC resistance of ferrite
+ impedance of line and connector
Unit Note
V I = 70mA
Imax = 150mA
V High (ON)
Low (OFF)
Issue 1 10/2003