Datasheet

FUNCTIONAL DESCRIPTION
ISOLATION VOLTAGE
Repeated High-Voltage Isolation Testing
APPLICATION INFORMATION
OPTIONAL INPUT/OUTPUT FILTERS
INPUT/OUTPUT CAPACITORS
+V
IN
DCH01xxxxSN7
-V
IN
+V
OUT
COM
2.2 mF
Ceramic
1 mH to 5 mH
4.7 mF
Ceramic
+V
IN
-V
IN
4.7 mF
1 mH to 5 mH
1 mF
UDG-08077
DCH01 Series
www.ti.com ........................................................................................................................................... SBVS073H – NOVEMBER 2006 – REVISED JANUARY 2009
The DCH01 series of DC/DC converters are 100% production tested at 3.5 kVDC for 1 second. The isolation test
voltage represents an operational isolation to transient voltages and should not be relied upon for safety
isolation.
The continuous voltage that can be applied across the DCH01 during normal operation must be < 60 VDC, within
SELV limits.
Repeated high-voltage isolation testing can degrade the isolation capability of the DCH01.
DCH01 power modules include internal input and output ceramic capacitors in all their designs. However, some
applications require much lower levels of either input reflected or output ripple/noise. This application note
describes various filters and design techniques found to be successful in reducing both input and output
ripple/noise.
The easiest way to reduce output ripple and noise is to add one or more ceramic capacitors each with a value of
4.7- µ F or greater. Ceramic capacitors should be placed close to the output power terminals. A single 4.7- µ F
ceramic capacitor reduces the output ripple/noise by 10% to 30%.
Switching regulators draw current from the input line in pulses at their operating frequency. The amount of
reflected (input) ripple/noise generated is directly proportional to the equivalent source impedance of the power
source including the impedance of any input lines. The addition of a 4.7- µ F ceramic capacitor, near the input
power pins, reduces reflected conducted ripple/noise by 30% to 50%.
The recommended capacitve load on the output of the DCH01 is 100 µ F.
Figure 20. DCH01 Series π Filter
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