ILC7082 Datasheet, PDF (6/16 Pages) Impala Linear Corporation – 150MA SOT-23 ULTRA LOW NOISE CMOS RF-LDO REGULATOR

ILC7082
Thermal Protection
The ILC7082 also includes a thermal protection circuit
which shuts down the regulator when die temperature
exceeds 170˚C due to overheating. In thermal shutdown,
once the die temperature cools to below 160˚C, the regulator
is enabled. If the die temperature is excessive due to high
package power dissipation, the regulator’s thermal circuit
will continue to pulse the regulator on and off. This is called
thermal cycling.
Excessively high die temperature may occur due to high dif-
ferential voltage across the regulator or high load current or
high ambient temperature or a combination of all three.
Thermal protection protects the regulator from such fault
conditions and is a necessary requirement in today’s designs.
In normal operation, the die temperature should be limited to
under 150˚C.
Adjustable Output Voltage
Figure 3 shows how an adjustable output voltage can be
easily achieved using ILC7082-ADJ. The output voltage,
V_OUT is given by the following equation:
V_OUT = 1.24V x (R1/R2 + 1)
V_OUT
R1
R2
5 ^SOT23-5 4 ^VADJ
C_OUT
V_IN
C_IN
ILC7083-ADJ
1
23
ON
OFF
Figure 3. Application Circuit for
Adjustable Output Voltage
For best results, a resistor value of 470kΩ or less may be
used for R2. The output voltage can be programmed from
2.5V to 12V.
Note: An external capacitor should not be connected to
the adjustable feedback pin (pin 4). Connecting an exter-
nal capacitor to pin 4 may cause regulator instability and
lead to unwanted oscillations.
Maximum Output Current
The maximum output current available from the ILC7082 is
limited by the maximum package power dissipation as well
as the device’s internal current limit. For a given ambient
temperature, TA, the maximum package power dissipation is
given by:
P_D(MAX) = (T_J(MAX) - T_A) / θ_JA
where T_J(MAX) = 150˚C is the maximum junction tempera-
ture and qJA = 333˚C/W is the package thermal resistance.
For example at T_A = 85˚C ambient temperature, the maxi-
mum package power dissipation is;
P_D(MAX) = 195mW
The maximum output current can be calculated from the
following equation:
I_OUT(MAX) < P_D(MAX) / (V_IN - V_OUT)
For example at V_IN = 6V, V_OUT = 5V and T_A = 85˚C, the
maximum output current is I_OUT(MAX) < 195mA. At higher
output current, the die temperature will rise and cause the
thermal protection circuit to be enabled.
Application Hints
Figure 4 shows the typical application circuit for the
ILC7082.
V_OUT
C_OUT
5 ^SOT23-5 4
ILC7082
C_NOISE
V_IN
1
C_IN
23
ON
OFF
Figure 4. Basic Application Circuit for Fixed
Output Voltage Versions
Input Capacitor
An input capacitor C_IN of value 1µF or larger should be con-
nected from V_IN to the main ground plane. This will help to
filter supply noise from entering the LDO. The input capaci-
tor should be connected as close to the LDO regulator input
pin as is practical. Using a high-value input capacitor will
offer superior line transient response as well as better power
supply ripple rejection. A ceramic or tantalum capacitor may
be used at the input of the LDO regulator.
6
REV. 1.6.2 11/17/04