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LTM8058MPY#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
LTM8058
10
8058fa
For more information www.linear.com/LTM8058
APPLICATIONS INFORMATION
For most applications, the design process is straight
forward, summarized as follows:
1. Look at Table 1a (or Table 1b, if the post linear regula
-
tor is used) and find the row that has the desired input
range and output voltage.
2. Apply the recommended C
IN
, C
OUT1
, C
OUT2
, R
ADJ1
,
R
ADJ2
and C
BYP
if required.
3. Connect BIAS as indicated, or tie to an external source
up to 15V or V
IN
, whichever is less.
While these component combinations have been tested for
proper operation, it is incumbent upon the user to verify
proper operation over the intended system’s line, load and
environmental conditions. Bear in mind that the maximum
output current may be limited by junction temperature,
the relationship between the input and output voltage
magnitude and polarity and other factors. Please refer
to the graphs in the Typical Performance Characteristics
section for guidance.
Capacitor Selection Considerations
The C
IN
, C
OUT1
and C
OUT2
capacitor values in Table 1 are
the minimum recommended values for the associated op-
erating conditions
.
Applying capacitor values below those
indicated in Table 1 is not recommended, and may result
in undesirable operation. Using larger values is generally
acceptable, and can yield
improved dynamic response, if
it
is necessary. Again, it is incumbent upon the user to
verify proper operation over the intended system’s line,
load and environmental conditions.
Ceramic capacitors are small, robust and have very low
ESR. However, not all ceramic capacitors are suitable.
X5R and X7R types are stable over temperature and ap
-
plied voltage
and give dependable service. Other types,
including Y5V and Z5U have very large temperature and
voltage coefficients of capacitance. In an application cir
-
cuit they may have only a small fraction of their nominal
capacitance resulting in much higher output voltage ripple
than expected.
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LTM8058. A
ceramic input capacitor combined with trace or cable
inductance forms a high-Q (underdamped) tank circuit. If
the LTM8058 circuit is plugged into a live supply, the input
voltage can ring to much higher than its nominal value,
possibly exceeding the device’s rating. This situation is
easily avoided; see the Hot-Plugging Safely section.
LTM8058 Table 1a. Recommended Component Values and Configuration for Specific V
OUT1
Voltages (T
A
= 25°C)
V
IN
V
OUT1
V
BIAS
C
IN
C
OUT1
R
ADJ1
3.1V to 31V 2.5V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 12.4k
3.1V to 31V 3.3V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 10k
3.1V to 29V 5V 3.1V to 15V or Open 2.2µF, 50V, 1206 22µF, 16V, 1210 6.98k
3.1V to 26V 8V 3.1V to 15V or Open 2.2µF, 50V, 1206 22µF, 10V, 1206 4.53k
3.1V to 24V 12V 3.1V to 15V or Open 2.2µF, 25V, 0805 10µF, 16V, 1210 3.16k/8.2pF*
9V to 15V 2.5V V
IN
2.2µF, 50V, 1206 100µF, 6.3V, 1210 12.4k
9V to 15V 3.3V V
IN
2.2µF, 50V, 1206 47µF, 6.3V, 1210 10k
9V to 15V 5V V
IN
2.2µF, 50V, 1206 22µF, 16V, 1210 6.98k
9V to 15V 8V V
IN
2.2µF, 50V, 1206 22µF, 10V, 1206 4.53k
9V to 15V 12V V
IN
2.2µF, 25V, 0805 10µF, 16V, 1210 3.16k
18V to 31V 2.5V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 12.4k
18V to 31V 3.3V 3.1V to 15V or Open 2.2µF, 50V, 1206 47µF, 6.3V, 1210 10k
18V to 29V 5V 3.1V to 15V or Open 2.2µF, 50V, 1206 22µF, 16V, 1210 6.98k
18V to 26V 8
V 3.1V to 15V or Open
2.2µF, 50V, 1206 22µF, 10V, 1206 4.53k
18V to 24V 12V 3.1V to 15V or Open 2.2µF, 50V, 1206 10µF, 16V, 1210 3.16k/8.2pF*
Note:
Do not allow BIAS to exceed V
IN
, a bulk input capacitor is required. If BIAS is open, the minimum V
IN
is 4.3V.
*Connect 3.16k in parallel with 8.2pF from ADJ1 to GND
LTM8058
11
8058fa
For more information www.linear.com/LTM8058
LTM8058 Table 1b. Recommended Component Values and Configuration for Specific V
OUT2
Voltages (T
A
= 25°C)
V
IN
V
OUT1
V
OUT2
V
BIAS
C
IN
C
OUT1
C
OUT2
R
ADJ1
R
ADJ2
3.1V to 31V 2.3V 1.2V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 133k Open
3.1V to 31V 2.3V 1.5V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 133k 2.32M
3.1V to 31V 2.3V 1.8V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 13.3k 1.07M
3.1V to 31V 3.08V 2.5V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 10.5k 487k
3.1V to 31V 3.92V 3.3V 3.1V to 15V or Open 2.2µF, 50V, 1206 47µF, 6.3V, 1210 10µF, 6.3V, 1206 8.66k 294k
3.1V to 29V 5.7V 5V 3.1V to 15V or Open 2.2µF, 50V, 1206 22µF, 16V, 1210 10µF, 6.3V, 1206 6.19k 162k
3.1V to 26V 8.85V 8V 3.1V to 15V or Open 2.2µF, 50V, 1206 22µF, 10V, 1206 10µF, 10V, 1206 4.12k 88.7k
3.1V to 21V 13V 12V 3.1V to 15V or Open 2.2µF, 25V, 0805 10µF, 16V, 1210 22µF, 16V, 1206 2.94k/22pF* 56.2k
9V to 15V 2.3V 1.2V V
IN
2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 133k Open
9V to 15V 2.3V
1.5V V
IN
2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 133k 2.32M
9V to 15V 2.3V 1.8V V
IN
2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 13.3k 1.07M
9V to 15V 3.08V 2.5V V
IN
2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 10.5k 487k
9V to 15V 3.92V 3.3V V
IN
2.2µF, 50V, 1206 47µF, 6.3V, 1210 10µF, 6.3V, 1206 8.66k 294k
9V to 15V 5.7V 5V V
IN
2.2µF, 50V, 1206 22µF, 16V, 1210 10µF, 6.3V, 1206 6.19k 162k
9V to 15V 8.85V 8V V
IN
2.2µF, 50V, 1206 22µF, 10V, 1206 10µF, 10V, 1206 4.12k 88.7k
9V to 15V 13V 12V V
IN
2.2µF, 25V, 0805 10µF, 16V, 1210 22µF, 16V, 1206 2.94k/22pF* 56.2k
18V to 31V 2.3V 1.2V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 133k Open
18V to 31V 2.3V 1.5V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 133k 2.32M
18V to 31V 2.3V 1.8V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 13.3k 1.07M
18V to 31V 3.08V 2.5V 3.1V to 15V or Open 2.2µF, 50V, 1206 100µF, 6.3V, 1210 10µF, 6.3V, 1206 10.5k 487k
18V to 31V 3.92V 3.3V 3.1V to 15V or Open 2.2µF, 50V, 1206
47µF, 6.3V, 1210 10µF, 6.3V, 1206
8.66k 294k
18V to 29V 5.7V 5V 3.1V to 15V or Open 2.2µF, 50V, 1206 22µF, 16V, 1210 10µF, 6.3V, 1206 6.19k 162k
18V to 26V 8.85V 8V 3.1V to 15V or Open 2.2µF, 50V, 1206 22µF, 10V, 1206 10µF, 10V, 1206 4.12k 88.7k
Note:
Do not allow BIAS to exceed V
IN
, a bulk input capacitor is required. If BIAS is open, the minimum V
IN
is 4.3V.
*Connect 2.94k in parallel with 22pF from ADJ1 to GND.
APPLICATIONS INFORMATION
BIAS Pin Considerations
The BIAS pin is the output of an internal linear regulator
that powers the LTM8058’s internal circuitry. It is set to 3V
and must be decoupled with a low ESR capacitor of at least
4.7μF. The LTM8058 will run properly without applying
a voltage to this pin, but will operate more efficiently and
dissipate less power if a voltage between 3.1V and V
IN
is
applied. At low V
IN
, the LTM8058 will be able to deliver
more output current if BIAS is 3.1V or greater. Up to 31V
may be applied to this pin, but a high BIAS voltage will
cause excessive power dissipation in the internal circuitry.
For applications with
an input voltage less than 15V, the
BIAS
pin is typically connected directly to the V
IN
pin. For
input voltages greater than 15V, it is preferred to leave the
BIAS pin separate from the V
IN
pin, either powered from
a separate voltage source or left running from the internal
regulator. This has the added advantage of keeping the
physical size of the BIAS capacitor small. Do not allow
BIAS to rise above V
IN
.
Soft-Start
For many applications, it is necessary to minimize the
inrush current at start-up. The built-in soft-start circuit
significantly reduces the start-up current spike and output
voltage overshoot by applying a capacitor from SS to GND.
When the LTM8058 is enabled, whether from V
IN
reaching
a sufficiently high voltage or RUN being pulled high, the
LTM8058 will source approximately 10µA out of the SS
pin. As this current gradually charges the capacitor from
SS to GND, the LTM8058 will correspondingly increase
the power delivered to the output, allowing for a graceful
turn-on ramp.
LTM8058
12
8058fa
For more information www.linear.com/LTM8058
APPLICATIONS INFORMATION
Isolation, Working Voltage and Safety Compliance
The LTM8058 isolation is 100% hi-pot tested by tying
all of the primary pins together, all of the secondary pins
together and subjecting the two resultant circuits to a
differential of 3kV DC for one second. This establishes
the isolation voltage rating of the LTM8058 component.
The isolation rating of the LTM8058 is not the same as
the working or operational voltage that the application
will experience. This is subject to the application’s power
source, operating conditions, the industry where the end
product is used and other factors that dictate design re
-
quirements such
as the gap between copper planes, traces
and component pins on the printed circuit board, as well
as the type of connector that may be used. To maximize
the allowable working voltage, the LTM8058 has two
columns of solder balls removed to facilitate the printed
circuit board design. The ball to ball pitch is 1.27mm, and
the typical ball diameter is 0.78mm. Accounting for the
missing columns and the ball diameter, the printed circuit
board may be designed for a metal-to-metal separation of
up to 3.03mm. This may have to be reduced somewhat to
allow for tolerances in solder mask or other printed circuit
board
design rules. For those situations where informa-
tion about
the spacing of LTM8058 internal circuitry is
required,
the minimum metal to metal separation of the
primary and secondary is 0.75mm.
To reiterate, the manufacturer’s isolation voltage rating
and the required working or operational voltage are of
-
ten different
numbers. In the case of the LTM8058, the
isolation
voltage rating is established by 100% hi-pot
testing. The working or operational voltage is a function
of the end product and its system level specifications. The
actual required operational voltage is often smaller than
the manufacturer’s isolation rating.
The LTM8058 is a UL recognized component under
UL 60950, file number
E464570. The UL 60950 insula-
tion category of the LTM8058 transformer is Functional.
Considering
UL 60950 Table 2N and the gap distances
stated above, 3.03mm external and 0.75mm internal,
the LTM8058 may be operated with up to 250V working
voltage in a pollution degree 2 environment. The actual
working voltage, insulation category, pollution degree and
other critical parameters for the specific end application
depend upon the actual environmental, application and
safety compliance requirements. It is therefore up to the
user to
perform a safety and compliance review to ensure
that the LTM8058 is suitable for the intended application.
V
OUT2
Post Regulator
V
OUT2
is produced by a high performance low dropout
300mA regulator. At full load, its dropout is less than
430mV. Its output is set by applying a resistor from the
R
ADJ2
pin to GND; the value of R
ADJ2
can be calculated
by the equation:
R
ADJ2
=
608.78
V
OUT2
–1.22
kΩ
ADJ1 and Line Regulation
For V
OUT1
greater than 8V, parasitics in the transformer
interacting with the controller cause a localized increase in
minimum load. A small capacitor may need to be applied
from ADJ1 to GND to ensure proper line regulation. Care
must be taken when choosing this capacitor value. Too
small or no capacitor will result in poor line regulation;
in general, a larger capacitor is needed for higher V
OUT1
.
Too large of a capacitance will require excessive minimum
load to maintain regulation.
The plots in Figure 1 show LTM8058 line regulation with
three different capacitor values applied from ADJ1 to GND.
V
IN
(V)
0
–5
DEVIATION (%)
–4
–2
–1
0
5
2
6
12
8058 F01
–3
3
4
1
18
24
NO CAP
8.2pF CAP
12pF CAP
Figure 1. V
OUT1
Line Regulation vs V
IN
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

LTM8058MPY#PBF

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Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 2kVAC Isolated, 1.5W Module DC/DC Converter with LDO Post Regulator
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