LT1580CT Linear Technology, LT1580CT Datasheet - Page 8

• Manufacturer Part Number: LT1580CT
• Description: IC LDO REGULATOR 7A ADJ TO220-5
• Manufacturer: Linear Technology

Specifications of LT1580CT

• Applications: Converter, Intel Pentium®
• Voltage - Input: 1.79 ~ 6 V
• Number Of Outputs: 1
• Voltage - Output: 1.25 ~ 4.65 V
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Through Hole
• Package / Case: TO-220-5 (Bent and Staggered Leads)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS
LT1580/LT1580-2.5
pin and the top of the resistor divider are connected to the
top of the load. The bottom of the resistor divider is
connected to the bottom of the load. R
connected inside the regulating loop of the LT1580 and the
load regulation at the load will be negligible for reasonable
8
3.3V
3.3V
Figure 3. Remote Sensing Improves Load Regulation
FIGURE 1
FIGURE 2
Figure 1. Conventional Load Sensing
V
V
POWER
POWER
Figure 2. Remote Load Sensing
V
V
I
OUT
OUT
OUT
V
V
LT1580
CONTROL
LT1580
CONTROL
U
ADJ
ADJ
5V
5V
R2
R2
( I
OUT
INFORMATION
SENSE
SENSE
U
R1
V
R1
)(R
V
OUT
OUT
P
)
TIME
W
P
R
R
R
R
P
P
P
P
is now effectively
1580 F03
LOAD
LOAD
U
1580 F01
+
V
–
1580 F02
+
V
–
OUT
OUT
values of R
output regulation. It is important to note that the voltage
drops due to R
dropout voltage of the regulator regardless of whether
they are inside the loop as in Figure 2 or outside the loop
as in Figure 1. This means that the LT1580 can control the
voltage at the load as long as the input-output voltage is
greater than the total of the dropout voltage of the LT1580
plus the voltage drop across R
Stability
The LT1580 requires the use of an output capacitor as part
of the device frequency compensation. The device re-
quires a minimum of 22 F tantalum or 150 F of aluminum
electrolytic to ensure stability. Larger capacitor values
increase stability and improve transient performance.
Many different types of capacitors are available and have
widely varying characteristics. These capacitors differ in
capacitor tolerance (sometimes up to 100%), equivalent
series resistance, equivalent series inductance and ca-
pacitance temperature coefficient. The LT1580 frequency
compensation optimizes frequency response with low
ESR capacitors. In general, use capacitors with an ESR of
less than 1 .
For microprocessor applications larger value capacitors
will be needed to meet the transient requirements of the
processor. Processor manufacturers require tight voltage
tolerances on the power supply. High quality bypass
capacitors must be used to limit the high frequency noise
generated by the processor. Multiple small ceramic ca-
pacitors in addition to high quality bulk tantalum capaci-
tors are typically required to limit parasitic inductance
(ESL) and resistance (ESR) in the capacitors to acceptable
levels. The LT1580 is stable with the type of capacitors
recommended by processor manufacturers.
Bypassing the adjust terminal on the LT1580 improves
ripple rejection and transient response. The ADJ pin is
brought out on the fixed voltage device specifically to
allow this capability.
Capacitor values on the order of several hundred microfar-
ads are used to ensure good transient response with heavy
P
. Trace B of Figure 3 illustrates the effect on
P
are not eliminated. They will add to the
P
.