Datasheet
LT6660
8
6660fa
APPLICATIO S I FOR ATIO
W UU
U
Longer Battery Life
Series references have a large advantage over older shunt
style references. Shunt references require a resistor
from the power supply to operate. This resistor must be
chosen to supply the maximum current that can ever be
demanded by the circuit being regulated. When the circuit
being controlled is not operating at this maximum current,
the shunt reference must always sink this current, resulting
in high dissipation and short battery life.
The LT6660 series references do not require a current
setting resistor and can operate with any supply voltage
from V
OUT
+ 0.9V to 20V. When the circuitry being regu-
lated does not demand current, the LT6660s reduce their
dissipation and battery life is extended. If the references
are not delivering load current, they dissipate only several
mW, yet the same connection can deliver 20mA of load
current when demanded.
Capacitive Loads
The LT6660 family of references are designed to be stable
with a large range of capacitive loads. With no capacitive
load, these references are ideal for fast settling or applica-
tions where PC board space is a premium. The test circuit
shown in Figure 1 is used to measure the response time
and stability of various load currents and load capacitors.
This circuit is set for the 2.5V option. For other voltage
options, the input voltage must be scaled up and the
output voltage generator offset voltage must be adjusted.
The 1V step from 2.5V to 1.5V produces a current step of
10mA or 1mA for R
L
= 100Ω or R
L
= 1k. Figure 2 shows
the response of the reference to these 1mA and 10mA
load steps with no load capacitance, and Figure 3 shows
a 1mA and 10mA load step with a 0.1µF output capaci-
tor. Figure 4 shows the response to a 1mA load step with
C
L
= 1µF and 4.7µF.
Figure 2. C
L
= 0µF
Figure 3. C
L
= 0.1µF
Figure 4. I
OUT
= 1mA
1µs/DIV
V
GEN
V
OUT
V
OUT
2.5V
1.5V
1mA
10mA
6660 F02
100µs/DIV
V
GEN
V
OUT
V
OUT
2.5V
1.5V
1mA
10mA
6660 F03
100µs/DIV
V
GEN
V
OUT
V
OUT
2.5V
1.5V
1µF
4.7µF
6660 F04
Figure 1. Response Time Test Circuit
LT6660-2.5
R
L
V
OUT
V
GEN
6660 F01
C
IN
0.1µF
2.5V
1.5V
C
L
V
IN
= 2.5V