E910.27A View Datasheet(PDF) - ELMOS Semiconductor AG
Part Name
Description
MFG CO.
'E910.27A' PDF : 50 Pages View PDF
- Preliminary -
E910.27A
The crossover losses are lowest at minimum input voltage. But they are usually a small fraction of the con-
duction losses, they can be sometimes ignored. For 100% duty cycle we get the worst case RMS current
through the internal P-channel MOS transistor.The maximum RMS current through the switch in continuous
conduction mode over duty cycle can be calculated by:
IPMOS RMS = IOUTMAX ⋅
Duty
1
+
r2
12
[36]
The effective ON-resistance of the E910.27 over junction temperature can be approximated by:
RDSON ≈ (470m + 1.41m ⋅TJ + 2.85µ ⋅TJ 2 ) ⋅ Ω
[37]
In continuous conduction mode the total device power loss can be approximated using the following equa-
tion:
( ( ) ) PDEVTOT ≈ VINPUT ⋅ IDQS + IPMOSRMS 2 ⋅ RDSON + VINPUT ⋅ Fop ⋅ 0.5 ⋅ IOUTMAX ⋅ tON + tOFF + QDS
[38]
Where:
tON = P-channel MOS transistor turn on time
tOFF = P-channel MOS transistor turn off time
QDS = P-channel MOS transistor gate driver charge
Typically values for the E910.27 are:
tON ~ 20ns
tOFF ~ 30ns
QDS ~ 10nQ
When maximum junction temperature and maximum operating temperature are known, their difference indi-
cates the permissible junction temperature rise for the given application. The thermal resistance path must
ensure that the product PDEV x RTAJ is lower than this difference. The maximum possible device power
loss can by calculated by:
PDEVMAX
≈ TJ MAX −TAMAX
RTAJ
[39]
Where:
TAMAX = maximum operating temperature
TJMAX = maximum save junction temperature, about 135°C
RTAJ = thermal resistance junction to ambient.
ELMOS Semiconductor AG
Specification 32 / 50
03SP0357E.00 05.09.2006
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