a
- 7 -
TDK-Lambda
CN-A24 Series
Instruction Manual
(3)
To adjust output voltage for whole range
Resistor values, as well as, connecting methods for
external resistor (R1) and external variable resistor(VR)
are described below.
5V 12V 24V
R1 5.6k 5.6k 5.6k
VR
2k
5k
10k
unit:[
Ω
]
External resistor
：±
5% Tolerance
External variable resistor
：±
20% Tolerance
with end resistance below 1%
Table 2-1 Values of External Resistor
and Variable Resistor
Vo :
–
10% - +20%(5V)
Vo :
–
10% - +10%(12V,24V)
Fig.2-5 Example of Connecting External Resistor
Output Voltage Adjustment by applying external
voltage
By applying external voltage at the TRM terminal,
output voltage can be adjusted within the same output
voltage adjustment range as the output voltage
adjustment by external resistor or variable resistor. In
this case, output voltage can be calculated by the
formula described below.
2.45
)
225
.
1
Voltage
Terminal
TRM
(
Voltage
Output
Nominal
Voltage
Output
+
´
=
225
.
1
Voltage
Output
Nominal
Voltage
Output
45
.
2
Voltage
Terminal
TRM
-
´
=
Fig.2-6 Example of applying external voltage
Note :
Please connect the amplifier so as not to interfere
in internal impedance of the trim circuit when you
apply the external voltage.
For applications other than the above, refer to the
TRM circuit as shown in fig.2-7 and determine external
circuit and components values.
Fig.2-7 Internal TRM Circuit (For the Reference)
3. Maximum Output Ripple and Noise
Measured value according to the specified methods
based on JEITA-9141 (Clause 7.12 and clause 7.13)
which is described in the following.
Connect according to fig.3-1 and measure. Connect
capacitors (C2 : ceramic capacitor , C3 : electrolytic
capacitor) at 50mm distance from the output terminals.
Measure at ceramic capacitor (C2) terminals as shown
in fig. 3-1 using coaxial cable with JEITA attachment.
Use oscilloscope with 100MHz frequency bandwidth or
equivalent.
Fig.3-1 Measurement of Maximum
Output Ripple and Noise
Take note that, PCB wiring design might influence
output spike noise.
Generally, increasing capacitance value of external
capacitor can reduce output ripple voltage and output
spike noise.
1k
Ω
1.225V
Reference
Voltage
1k
Ω
OP amp at Voltage monitor
+S
TRM
1k
Ω
-S
Load
R1
VR
C3
C2
+V
-V
+S
-S
TRM
+
-
CN100A24
+S
-S
+V
-V
TRM
+
-
Load
C3
C2
CN-A110
CN-A24
CN-A24
CN-A24
