Datasheet
LTC6090
11
6090fa
applicaTions inForMaTion
Figure 1. Low Voltage Interface
6090 F01
OD
COM
LTC6090
TFLAG
10k
LOW VOLTAGE
SUPPLY
TIE TO LOW
VOLTAGE GROUND
TO LOW
VOLTAGE
CONTROL
TO LOW
VOLTAGE
CONTROL
10k
200k
V
+
V
–
V
–
2M
V
+
2M
2M
10k
10k
30k
500Ω
Figure 2. Starting Up
Figure 3. LTC6090 Output Disable Function
1ms/DIV
6090 F02
OUT
10V/DIV
V+
2.5ms/DIV
6090 F03
OUT
2V/DIV
OD
2V/DIV
For simplest shutdown operation, float the COM pin, and
tie the OD pin to the TFLAG pin. This will float the low
voltage control pins, and the overtemperature circuit will
safely shutdown the output stage if the die temperature
reaches 145°C.
Since the OD pin is referenced to the COM pin, precaution
should be exercised and the absolute maximum ratings
should be observed for the COM and OD pins.
When coming out of shutdown the LTC6090 bias circuits
and input stage are already powered up leaving only the
output stage to turn on and drive to the proper output
voltage. Figures 2 and 3 show the part starting up and
coming out of shutdown, respectively.
Thermal Shutdown
The TFLAG pin is an open drain output pin that sinks 120µA
(typical) when the die temperature exceeds 145°C. The
temperature sensor has 5°C of hysteresis requiring the
part to cool to 140°C before disabling the TFLAG pin. Since
the TFLAG pin is referenced to the COM pin, precaution
should be exercised and the absolute maximum ratings
should be observed for the COM and TFLAG pins.
Tying the TFLAG pin to the OD pin will automatically shut
down the output stage when the die temperature
exceeds
145°C as shown in Figure 4. This will ensure that the junc-
tion temperature does not exceed 150°C.
For safety, an independent second overtemperature
threshold shuts down the output stage if the internal die
temperature rises to 175°C. There is hysteresis in the
thermal shutdown circuit requiring the die temperature
to cool 7°C. Once the device has cooled sufficiently, the
output stage will enable. Degradation can occur or reli-
ability may be affected when the junction temperature
of the device exceeds 150°C.