LT3013 LINER [Linear Technology], LT3013 Datasheet - Page 14

• Manufacturer Part Number: LT3013
• Description: 250mA, 4V to 80V Low Dropout Micropower Linear Regulator with PWRGD
• Manufacturer: LINER [Linear Technology]

LT3013
APPLICATIONS INFORMATION
Figure 4 shows a block diagram of the PWRGD circuit. At
startup, the timing capacitor is discharged and the PWRGD
pin will be held low. As the output voltage increases and
the ADJ pin crosses the 90% threshold, the JK fl ip-fl op
is reset, and the 3μA current source begins to charge the
timing capacitor. Once the voltage on the C
the V
capacitor voltage is clamped and the PWRGD pin is set to
a high impedance state.
During normal operation, an internal glitch fi lter will ignore
short transients (<15μs). Longer transients below the 90%
threshold will reset the JK fl ip-fl op. This fl ip-fl op ensures
that the capacitor on the C
the way to the V
time delay. This provides a consistent time delay after the
ADJ pin is within 10% of the regulated voltage before the
PWRGD pin switches to high impedance.
14
CT(HIGH)
threshold (approximately 1.7V at 25°C), the
CT(LOW)
threshold before re-starting the
ADJ
V
T
REF
pin is quickly discharged all
• 90%
+
–
Figure 4. PWRGD Circuit Block Diagram
T
pin reaches
J
K
Q
I
CT
3µA
+
–
C
Thermal Considerations
The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C for
LT3013E or 140°C for LT3013HFE). The power dissipated
by the device will be made up of two components:
1. Output current multiplied by the input/output voltage
2. GND pin current multiplied by the input voltage:
The GND pin current can be found by examining the GND
Pin Current curves in the Typical Performance Character-
istics. Power dissipation will be equal to the sum of the
two components listed above.
The LT3013 has internal thermal limiting designed to pro-
tect the device during overload conditions. For continuous
normal conditions the maximum junction temperature
rating of 125°C (E-grade) or 140°C (H-grade)must not be
exceeded. It is important to give careful consideration to
all sources of thermal resistance from junction to ambi-
ent. Additional heat sources mounted nearby must also
be considered.
T
V
~0.1V
CT(LOW)
differential: I
I
GND
• V
IN
.
V
(~1.1V)
CT(HIGH)
OUT
– V
• (V
BE
IN
– V
PWRGD
3013 F04
OUT
) and,
3013fc