a705ngt-350 ADD Microtech Inc., a705ngt-350 Datasheet - Page 5

• Manufacturer Part Number: a705ngt-350
• Description: High Power Advanced Current Regulator
• Manufacturer: ADD Microtech Inc.

The Maximum Power Dissipation on Regulator:
Thermal Consideration:
conditions. When power consumption is over about 700mW (SOT-89 package, at T
package, at T
of copper foil required. For multi-layered PCB, these layers can also be used as a heat sink. They can be connected with
several through-hole vias.
Copyright © 2009 ADDtek Corp.
PCB heat sink size (mm
PCB θ
P
The maximum junction temperature ratings of A705 should not be exceeded under continuous normal load
The junction temperature is:
T
If PC Board copper is going to be used as a heat sink, below table can be used to determine the appropriate size
D(MAX)
J
= P
V
I
I
V
P
θ
θ
θ
OUT(NOM)
Q
A
D
D
OUT(MAX)
IN(MAX)
SA
=70°C), additional heat sink is required to control the junction temperature below 120°C.
JT
CS
SA
= the quiescent current the regulator consumes at I
= V
(θ
:  T hermal resistance from the junction to the mounting tab of the package.
: Dissipated power.
:  T hermal resistance through the interface between the IC and the surface on which it is mounted.
(°C /W)
For SOT-89 package, θ
(typically, θ
:  T hermal resistance from the mounting surface to ambient (thermal resistance of the heat sink).
JT
OUT(MAX)
= the maximum input voltage.
= the nominal output current;
= the maximum voltage on output pin;
+θ
2
CS
)
+θ
CS
× I
< 1.0°C /W)
SA
500
OUT(NOM)
59
Recommended figure of PCB area used as a heat sink.
) + T
Through-hole vias
JT
= 35.0 °C /W. For TO-252 package, θ
A
+ V
1000
45
IN(MAX)
Heat-pad of TO-252
5
1500
× I
38
Q
VDD
GND
OUT
OUT(MAX)
2000
;
33
JT
= 7.0 °C /W.
3000
27
A
=70°C) or 1000mW (TO-252
DD077_D -- JULY 2009
4000
24
A705
5000
21