LT6650
10
6650fa
APPLICATIO S I FOR ATIO
WUU
U
Figure 11. Worst-Case 0°C to 70°C Hysteresis Figure 12. Worst-Case –40°C to 85°C Hysteresis
V
OUT
. R
B
must be within the following range for proper
operation (the optimal value depends greatly on the direc-
tion and magnitude of the load current):
R
B
> |V
S
– V
OUT
|/(200µA + 0.4/R
G
)
R
B
< |V
S
– V
OUT
|/(15µA + 0.4/R
G
)
Hysteresis
Due to various mechanical stress mechanisms inherent to
integrated-circuit packaging, internal offsets may not pre-
cisely recover from variations that occur over tempera-
ture, and this effect is referred to as hysteresis. Proprietary
manufacturing steps minimize this hysteresis, though
some small residual error can occur. Hysteresis measure-
ments for the LT6650 can be seen in Figures 11 and 12.
Figure 11 presents the worst-case data taken on parts
subjected to thermal cycling between 0°C to 70°C, while
Figure 12 shows data for –40°C to 85°C cycling. Units
were cycled several times over these temperature ranges
and the largest changes are shown. As would be expected,
the parts cycled over the higher temperature extremes
exhibit a broader hysteresis distribution. The worst hys-
teresis measurements indicate voltage shifts of less than
1000ppm (0.1%) from their initial value.
Limits of Operation
The LT6650 is a robust bipolar technology part. ESD
clamp diodes are integrated into the design and are
depicted in the Simplified Schematic for reference. Diodes
are included between the GND pin and the IN, OUT, and FB
pins to prevent reverse voltage stress on the device.
Unusual modes of operation that forward-bias any these
diodes should limit current to 10mA to avoid permanent
damage to the device. The LT6650 is fabricated using a
relatively high-voltage process, allowing any pin to inde-
pendently operate at up to 20V with respect to GND. The
part does not include any over voltage protection mecha-
nisms; therefore caution should be exercised to avoid
inadvertent application of higher voltages in circuits in-
volving high potentials.
DISTRIBUTION (ppm)
–400
NUMBER OF UNITS
2
3
6
5
4
400
6650 F11
1
0
–200
0
200
600
LIGHT COLUMNS 0°C TO 25°C
DARK COLUMNS 70°C TO 25°C
DISTRIBUTION (ppm)
–1000
NUMBER OF UNITS
2
3
6
5
4
500
6650 F12
7
1
0
–500
1000
250
–750
–250
0
750
LIGHT COLUMNS –40°C TO 25°C
DARK COLUMNS 85°C TO 25°C
