EV1320QI Datasheet, PDF (17/20 Pages) Enpirion, Inc. – The EV1320QI is a DC to DC converter specifically designed for memory termination applications.

Thermal Considerations
Thermal considerations are important physical
limitations that cannot be avoided in the real world.
Whenever there are power losses in a system, the
heat that is generated by the power dissipation
needs to be accounted for.
The Enpirion EV1320QI VDDQ/VTT Converter is
packaged in a 3x3x0.55mm 16-pin QFN package.
The recommended maximum junction temperature
for continuous operation is 125°C. Continuous
operation above 125°C may reduce long-term
reliability. The device has a thermal overload
protection circuit designed to turn off the device at
an approximate junction temperature value of
150°C.
The EV1320QI is guaranteed to support the full 2A
output current up to 85°C ambient temperature.
The following example and calculations illustrate
the thermal performance of the EV1320QI.
Example:
VDDQ = 1.2V
VTT = 0.6V
I_OUT = 2A
First calculate the output power.
P_OUT = VTT * I_OUT = 0.6V x 2A = 1.2W
Next, determine the input power based on the
efficiency (η) shown in Figure 8.
Efficiency vs. Output Current
96
94
92
90
88
92.6%
86
84
CONDITIONS
82
VTT = 0.6V
AV_IN = 3.0V
VDDQ = 2* VTT
80
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
OUTPUT CURRENT (A)
Figure 8: Efficiency vs. Output Current
For VDDQ = 1.2V, VTT = 0.6V at 2A, η ≈ 92.6%
η = P_OUT / P_IN = 92.6% = 0.926
EV1320QI
P_IN = P_OUT / η
P_IN ≈ 1.2W / 0.926 ≈ 1.2959W
The power dissipation (P_D) is the power loss in the
system and can be calculated by subtracting the
output power from the input power.
P_D = P_IN – P_OUT
≈ 1.2959W – 1.2W ≈ 0.0959W
With the power dissipation known, the temperature
rise in the device may be estimated based on the
theta JA value (θ_JA). The θ_JA parameter estimates
how much the temperature will rise in the device for
every watt of power dissipation. The EV1320QI has
a θ_JA value of 50 ºC/W without airflow.
Determine the change in temperature (∆T) based
on P_D and θ_JA.
∆T = P_D x θ_JA
∆T ≈ 0.0959W x 50°C/W = 4.795°C ≈ 4.8°C
The junction temperature (T_J) of the device is
approximately the ambient temperature (T_A) plus
the change in temperature. We assume the initial
ambient temperature to be 25°C.
T_J = T_A + ∆T
T_J ≈ 25°C + 4.8°C ≈ 29.8°C
With 0.0959W dissipated into the device, the T_J will
be 29.8°C.
The maximum operating junction temperature
(T_JMAX) of the device is 125°C, so the device can
operate at a higher ambient temperature. The
maximum ambient temperature (T_AMAX) allowed can
be calculated.
T_AMAX = T_JMAX – P_D x θ_JA
≈ 125°C – 4.8°C ≈ 120.2°C
The ambient temperature can actually rise by
another 95.2°C, bringing it to 120.2°C before the
device will reach T_JMAX. This indicates that the
EV1320QI can support the full 2A output current
range up to approximately 120.2°C ambient
temperature given the input and output voltage
conditions. This allows the EV1320QI to guarantee
full 2A output current capability at 85°C with room
for margin. Note that the efficiency will be slightly
lower at higher temperatures and these calculations
are estimates.
©Enpirion 2012 all rights reserved, E&OE
06831
Enpirion Confidential
April 9, 2012
www.enpirion.com, Page 17
Rev: C