CM2596S_06 Datasheet, PDF (10/13 Pages) Champion Microelectronic Corp. – 3A STEP DOWN VOLTAGE REGULATOR

CM2596S
3A STEP DOWN VOLTAGE REGULATOR
Feedback Connection
For fixed output voltage version, the FB (feedback) pin must be connected to V_OUT. For the adjustable version, it is important to
place the output voltage ratio resistors near CM2596S as possible in order to minimize the noise introduction.
Enable
It is required that the ENABLE must not be left open. For normal operation, connect this pin to a “LOW” voltage (typically, below
1.6V). On the other hand, for standby mode, connect this pin with a “HIGH” voltage. This pin can be safely pulled up to +V_IN
without a resistor in series with it.
Grounding
To maintain output voltage stability, the power ground connections must be low-impedance. For the 5-lead TO-220 and TO-263
style package, both the tab and pin 3 are ground and either connection may be used.
Heatsink and Thermal Consideration
Although the CM2596S requires only a small heatsink for most cases, the following thermal consideration is important for all
operation. With the package thermal resistances θJA and θJC, total power dissipation can be estimated as follows:
P_D = (V_IN x I_Q) + (V_OUT / V_IN)(I_LOAD x V_SAT);
When no heatsink is used, the junction temperature rise can be determined by the following:
ΔT_J = P_D x θ_JA;
With the ambient temerpature, the actual junction temperature will be:
T_J = ΔT_J + T_A;
If the actual operating junction temperature is out of the safe operating junction temperature (typically 125℃), then a heatsink is
required. When using a heatsink, the junction temperature rise will be reduced by the following:
ΔT_J = P_D x (θ_JC + θ_interface + θ_Heatsink);
Also one can see from the above, it is important to choose an heatsink with adequate size and thermal resistance, such that to
maintain the regulator’s junction temperature below the maximum operating temperature.
Layout guideline
As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance can generate
voltage transients which can cause problems. For minimal inductance and ground loops, the wires indicated by heavy lines
should be wide printed circuit traces and should be kept as short as possible. For best results, external components should
be located as close to the switcher lC as possible using ground plane construction or single point grounding.
If open core inductors are used, special care must be taken as to the location and positioning of this type of inductor. Allowing
the inductor flux to intersect sensitive feedback, lC ground path and COUT wiring can cause problems.
When using the adjustable version, special care must be taken as to the location of the feedback resistors and the associated
wiring. Physically locate both resistors near the IC, and route the wiring away from the inductor, especially an open core type of
inductor. (See application section for more information.)
2006/11/27 Rev 1.0
Champion Microelectronic Corporation
Page 10