Texas Instruments TRF4900, User Manual, Page: 21 / 45

2-10
2.3 EVM DC Voltage Setup
The evaluation board should be used with a dc power supply voltage of 8 V
nominal. Figure 2−1 details the dc voltage supply setup for the TRF4900 EVM.
Figure 2−1. TRF4900 EVM DC Voltage Setup
Vin is equal to 8 V
in
Vout for LM317 voltage regulator is equal to:
V at terminal 3 of LM317 should be 2 V to 3 V
higher than V out
V = 7.2 V
equal to 8 V,
nominal.
With V
1
2
4
R33
LED3
VCC
LN1271R−(TR)
0
JP4
R31 C17 C18 C19
2.0 − 3.8 V (3.0 V TYP)
VCC2
3.3V
C22 C21
C20
R35
VCC1
S1JB
CR5
RED
8.0V
ZR1
SMBJ8.5CA
POWER
C15
R34
C16
2
3
R32
3
VIN
2
VOUT
1
ADJ
LM317MDT
VR1
VI
3 VO
VO
ADJ
5
NC
6
VO
7
VO
8
NC
VR2
LM317LBD
R36
10
µ
F
0.1
µ
F
220
Ω
500
Ω
220
Ω
1
µ
F 0.1
µ
F 0.01
µ
F
360
Ω
1
µ
F 0.1
µ
F 0.01
µ
F
220
Ω
360
Ω
Vadj Used to Change
Vout From 2.2 V to 3.6 V
GROUND CLIPS
TP4 TP2 TP3
Vout = 1.25(1
+
((R32
+
R34)/R31))