LM26420YMH/NOPB National Semiconductor, LM26420YMH/NOPB Datasheet - Page 16

IC REG SYNC BUCK DL 2A 20-TSSOP

LM26420YMH/NOPB

Manufacturer Part Number
LM26420YMH/NOPB
Description
IC REG SYNC BUCK DL 2A 20-TSSOP
Manufacturer
National Semiconductor
Series
PowerWise®r
Type
Step-Down (Buck)r
Datasheet

Specifications of LM26420YMH/NOPB

Internal Switch(s)
Yes
Synchronous Rectifier
Yes
Number Of Outputs
2
Voltage - Output
0.8 ~ 4.5 V
Current - Output
2A
Frequency - Switching
550kHz
Voltage - Input
3 ~ 5.5 V
Operating Temperature
-40°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
20-TSSOP Exposed Pad, 20-eTSSOP, 20-HTSSOP
Primary Input Voltage
5.5V
No. Of Outputs
2
Output Voltage
4.5V
Output Current
2A
No. Of Pins
20
Operating Temperature Range
-40°C To +125°C
Msl
MSL 1 - Unlimited
Filter Terminals
SMD
Rohs Compliant
Yes
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Power - Output
-
Other names
LM26420YMH
www.national.com
To determine the maximum allowed resistor tolerance , use
the following equation:
where TOL is the set point accuracy of the regulator, Φ is the
tolerance of V
Example:
VOUT = 2.5V, with a set point accuracy of +/- 3.5%.
Choose 1% resistors. If R2 = 10kΩ, then R1 is 21.25kΩ.
VINC FILTERING COMPONENTS
Additional filtering is required between VINC and AGND in
order to prevent high frequency noise on VIN from disturbing
the sensitive circuitry connected to VINC. A small RC filter can
be used on the VINC pin as shown below.
In general, R
steady state voltage drop across the resistor due to the VINC
bias current does not affect the UVLO level. C
from 0.22 µF to 1.0 µF in X7R or X5R dielectric, where the RC
F
FB
FIGURE 5. Programming V
FIGURE 6. RC filter on VINC
is typically between 1Ω and 10Ω so that the
.
V
REF
= 0.80V
30069699
OUT
F
30069638
can range
16
time constant should be at least 2 µS. C
close as possible to IC with a direct connection from VINC
and AGND.
USING PRECISION ENABLE AND POWER GOOD
The LM26420's precision enable and power good pins ad-
dress many of the sequencing requirements required today's
challenging applications. Each output can be controlled inde-
pendently and have independent power goods. This allows
for a multitude of ways to control each output. Typically, the
enables to each output are tied together to the input voltage
and the outputs will ratiometrically ramp up when the input
voltage reaches above UVLO rising threshold. There may be
instances where it is desired that the second output (V
does not turn on until the first output (V
of the desired set-point. This achieved easily with an external
resistor divider attached from V
If it is not desired to have a resistor divider to control V
with V
control V
the range of 10kΩ to 100kΩ, 50kΩ is the suggested value.
greater. This will turn on V
90% of the programmed output. NOTE, this will also turn off
V
output.
Another example might be that the output is not to be turned
on until the input voltage reaches 90% of desired voltage set-
point. This verifies that the input supply is stable before turn-
ing on the output. Select R
voltage at the EN pin is greater than 1.12V when reaching the
90% desired set-point.
FIGURE 7. V
OUT2
OUT1
when V
OUT2
, then the PG
FIGURE 8. PG
, see figure below. R
OUT1
OUT1
controlling V
is outside the +/-10% of the programmed
1
can be connected to the EN
OUT2
1
EN1
controlling V
OUT1
when V
and R
OUT2
PG1
to EN
OUT1
with resistor divider.
is a pull up resistor on
EN2
OUT1
F
should be placed as
) has reached 90%
2
such that the the
, see figure .
OUT2
is approximately
30069640
30069697
.
2
pin to
OUT2
OUT2
)

Related parts for LM26420YMH/NOPB