LT6650CS5 LINER [Linear Technology], LT6650CS5 Datasheet - Page 9

• Manufacturer Part Number: LT6650CS5
• Description: Micropower, 400mV Reference with Rail-to-Rail Buffer Amplifier in SOT-23
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
step between 100 A and 200 A in Figure 7. Load step settling
occurs in about 0.5ms or less (to 0.2%).
Output Adjustment
If the LT6650 is to be used as a 400mV reference, then the
output and feedback pins may be tied together without any
scale-setting components as shown in the front-page
application circuit. Setting the output to any higher voltage
is a simple matter of selecting two feedback resistors to
configure the non-inverting gain of the internal operational
amplifier, as shown in Figure 8. A feedback resistor R
connected between the OUT pin and the FB pin, and a gain
resistor R
resistor values are related to the output voltage by the
following relationship:
The I
generally be neglected when R
R
G
V
S
10mV/DIV
Figure 7. Output Response to Current-Sinking Load Step
FB
20k, even worst-case I
200 A
100 A
Figure 8. Typical Configuration for Output Voltages
V
I
1k
OUT
OUT
AC
term represents the FB pin bias current, and can
R
F
G
= R
is connected from the FB pin to GND. The
1 F
G
• (V
U
IN
OUT
Greater than 0.4V
(100 A to 200 A)
4
LT6650
GND
– 0.4)/(0.4 – I
2
U
OUT
FB
5
FB
1
can be neglected (error
G
V
1nF
is 100k or less. For
W
OUT
= 0.4V • (1 + R
FB
R
R
• R
F
G
6650 F07
6650 F08
G
)
U
F
/R
G
1 F
)
V
OUT
F
is
contribution <0.15%). Since the V
increases at twice the resistor tolerance, high accuracy
resistors or resistor networks are recommended. The
output voltage may be set to any level from 400mV up to
350mV below the supply voltage with source or sink
capability.
Noise Reduction Capacitor
In applications involving the use of resistive feedback for
reference scaling, the intrinsic reference noise is amplified
along with the DC level. To minimize noise amplification,
the use of a 1nF feedback capacitor is recommended, as
shown in Figure 8 and other circuits with scaling resistors.
Shunt Reference Operation
The circuits shown in Figure 9 and Figure 10 form adjust-
able shunt references. Along with the external bias resistor
R
operation for outputs between 1.4V and 18V (positive or
negative). Just like a Zener diode, a supply V
somewhat higher in magnitude than the desired reference
Figure 9. Typical Configuration of LT6650 as Adjustable Positive
B
, the LT6650 provides positive or negative reference
Figure 10. Typical Configuration of LT6650 as Adjustable
V
IN
IN
S
4
4
R
LT6650
LT6650
B
GND
GND
–V
2
S
Negative Shunt Reference
2
R
OUT
B
OUT
5
FB
FB
5
Shunt Reference
1
1
V
V
OUT
1nF
1nF
OUT
= –0.4V • (1 + R
= 0.4V • (1 + R
R
R
R
R
F
G
F
G
OUT
6650 F09
F
error distribution
F
6650 F10
/R
/R
G
G
10 F
10 F
)
)
LT6650
V
V
S
OUT
OUT
is required,
9
6650f