Tool/software:
Hi Team,
One of my customer is using TPS62120 to power up the Radio module.
Input voltage - 9V
Output voltage - 3.3V
Active state current is 10mA for few mSeconds & most of the time it is in sleep mode where expected current is less than 100uA. 95% time device rmains in sleep.
They have already used this device & working fine but now they want to use same design for ambient temperatue which can go beyond 85 deg. C (likely 95 Deg. C of abmbient).
Do you see any issue with this operating condition with device relaiblity?
As per me ambient temperature mention in datasheet is relevant when devie operates in full power with worst case efficiency or with higher power drop. When you are operating with small percentage of power dissipation then junction temperatue is the right way to look into.
If I assume efficiency of 50% with my output power current requirement then also device should not see more than 20 Deg.C than ambient.
Output power = 3.3V X 10mA = 33mWatt
50 % efficency means power disspiation of 33mWatt, I am assuming total loss across the device & all other components as ideal.
(33 * 259.7) / 1000 = 9 deg. C rise. This calcualtion is based on JEDEC PCB guide line. In this case customer PCB may not be the same & hence adding margin of 10 Deg. C more. Still junction temperaure is not touching to the mentioned temperaure of 125 Deg. C so can we safely say that device can work beyond rated ambient if power dissipation across the device is managed within safe limits? Off course numbers are difficult to predict but message I want to convey to customer is "always look for the junction temperaure rather than the TA mentioned in datasheet".
Pls. help with the insight on this topic.
Mitesh
