Application Note
Derating
The operating case temperature range of the CHB75 series is -40˚C to +100˚C. When operating the CHB75 , proper derating
or cooling is needed .
Following is the derating curve of CHB75 without heat sink
Remote ON/OFF Control
The CHB75 series allows the user to switch the module on and off electronically with remote on/off feature. The CHB75 series
are available with "positive logic" or "negative logic" (option).
Logic Table
ON/OFF (2)
Logic State
(PIN 2)
Negative Logic
Positive Logic
Power Dissipated vs Ambient Temperature and Air Flow
25
Power Disspated, Pd (Watts)
Natural Convection
20 ft./min. (0.1 m/s)
100 ft./min. (0.5 m/s)
HIGH SIGNAL HERE
DISABLE OUTPUT
-VIN (4)
Logic Low -
Switch Closed
Logic High -
Switch Open
Module on
Module off
20
Module off
Module on
15
200 ft./min. (1.0 m/s)
10
300 ft./min. (1.5 m/s)
5
External Output Trimming
Output may optionally be externally trimmed
400 ft./min. (2.0 m/s)
0
0
10
20
30
40
50
60
70
80
90
100
(±10%) with a fixed resistor or an external trim-
pot as shown.
+SENSE (8)
TRIM DOWN
+SENSE (8)
Ambient Temperature, Ta(Deg. C)
TRIM (7)
TRIM (7)
10K ohms
TRIMPOT
Forced Convection Power Derating with No Heat Sink
TRIM UP
-SENSE (6)
-SENSE (6)
Where:
The power dissipation (Pd):
Pd = Pi - Po = Po (1-
)/
The thermal resistance are list below:
Output Noise
The output noise is measured with 10µF tantalum capacitor and 1.0µF ceramic capacitor across output.
TYPICAL Rca
7.12
˚C
/W
6.21
˚C
/W
5.17
˚C
/W
4.29
˚C
/W
3.64
˚C
/W
Resistor
Load
Ceramic
1.0µF
+Vout (9)
Chart of Thermal Resistance vs Air Flow:
AIR FLOW RATE
Natural Convection
100 ft./min.
200 ft./min.
300 ft./min.
400 ft./min.
The temperature rise (
T ):
T = Pd * Rca
-Vout (5)
Solid tantalum
10µF
To
Scope
Output Noise Test Circuit schematic
75
All Specifications Typical At Nominal Line, Full Load and 25˚C Unless Otherwise Noted.
76
CHB75
RSG [ RSG ELECTRONIC COMPONENTS GMBH ]
