LT3007 Series
14
3007fa
For more information www.linear.com/LT3007
The maximum junction temperature equals the maximum
junction temperature rise above ambient plus the maximum
ambient temperature or:
T
J(MAX)
= 85°C + 14.2°C = 99.2°C
High Temperature Operation
Care must be taken when designing LT3007 applications to
operate at high ambient temperatures. The LT3007 works
at elevated temperatures but erratic operation can occur
due to unforeseen variations in external components.
Some tantalum capacitors are available for high tempera
-
ture operation,
but ESR is often several Ohms; capacitor
ESR above 3Ω is unsuitable for use with the LT3007.
Ceramic capacitor manufacturers (Murata, AVX, TDK,
and Vishay at the time of this writing) now offer ceramic
capacitors that are rated to 150°C using an X8R dielectric.
Device instability will occur if the output capacitor value
and ESR are outside design limits at elevated tempera
-
ture and operating
DC voltage bias (see information on
capacitor characteristics under Output Capacitance and
Transient Response). Check each passive component
for absolute value and voltage ratings over the operating
temperature range.
APPLICATIONS INFORMATION
Operation of the LT3007 at temperatures above 125°C
requires careful selection of external components to
ensure output regulation, stability and optimal transient
response. Figures 9 and 10 have curves showing power
device leakage (from IN
to OUT) for the LT3007 in both
active
and shutdown states. The minimum external load
must be greater than this leakage to prevent the OUT pin
from rising out of regulation due to power device leakage.
Power device leakage decreases if the LT3007 is active;
if IN is tied directly to SHDN, the minimum required load
is reduced. The recommended minimum external load is
20µA. The use of a feedforward capacitor is required for
operation at temperatures above 135°C (see Feedforward
Capacitance section). For output voltages of 1.2V and
above, the feedforward capacitor ensures good transient
response. Use of the LT3007 at temperatures above 135°C
and output voltages under 1.2V is not advised.
Leakage in capacitors, or from solder flux left after insuf
-
ficient board
cleaning, adversely affects the low quiescent
current
operation. Consider junction temperature increase
due to power dissipation in both the junction and nearby
components to ensure maximum specifications are not
violated for the LT3007 or external components.
Figure 9. Power Device Leakage, SHDN = 0V
Figure 10. Power Device Leakage, SHDN = 1.5V
TEMPERATURE (°C)
100
POWER DEVICE LEAKAGE (μA)
10
1
9
7
5
3
8
6
4
2
0
3007 F09
150120 140110 130
V
OUT
= 0V
V
ADJ
= 0V
V
IN
= 45V
V
IN
= 2.1V
TEMPERATURE (°C)
100
POWER DEVICE LEAKAGE (μA)
2.0
0.2
1.8
1.4
1
0.6
1.6
1.2
0.8
0.4
0
3007 F10
150120 140110 130
V
OUT
= 0V
V
ADJ
= 0.7V
V
IN
= 45V
V
IN
= 2.1V
