LTM8046 데이터 시트보기 (PDF) - Linear Technology
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LTM8046 Datasheet PDF : 20 Pages
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LTM8046
Applications Information
For most applications, the design process is straight-
forward, summarized as follows:
1. Look at Table 1 and find the row that has the desired
input range and output voltage.
2. Apply the recommended CIN, COUT and RFB.
3. Connect BIAS as indicated, or tie to an external source
up to 15V or VIN, 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 CIN and COUT capacitor values in Table 1 are the
minimum recommended values for the associated oper-
ating 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 LTM8046. A
ceramic input capacitor combined with trace or cable
inductance forms a high-Q (underdamped) tank circuit. If
the LTM8046 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.
Table 1. Recommended Components and Configuration (TA = 25°C)
VIN
VOUT
CIN
COUT
3.2V to 32V
1.8V
1µF, 50V, 0805 X5R
2 × 100µF, 6.3V, 1206 X5R
3.2V to 31V
2.5V
1µF, 50V, 0805 X5R
2 × 100µF, 6.3V, 1206 X5R
3.2V to 29V
3.3V
1µF, 50V, 0805 X5R
100µF, 6.3V, 1206 X5R
3.2V to 26V
5V
1µF, 25V, 0603 X5R
100µF, 6.3V, 1206 X5R
3.2V to 20V
8V
1µF, 25V, 0603 X5R
47µF, 10V, 1206 X5R
3.2V to 12V
12V
1µF, 25V, 0603 X5R
2 × 10µF, 16V, 1210 X5R
3.2V to 25V
2.5V
1µF, 25V, 0603 X5R
2 × 100µF, 6.3V, 1206 X5R
3.2V to 25V
3.3V
1µF, 25V, 0603 X5R
100µF, 6.3V, 1206 X5R
CBIAS = 1µF 10V 0402 X5R
BIAS = 3.3V for VIN ≥ 3.3V, VIN for VIN < 3.3V. If BIAS = VIN, the minimum input voltage is 4.3V.
RFB
18.7k
14.7k
11.8k
8.45k
5.49k
3.83k
14.7k
11.8k
10
For more information www.linear.com/LTM8046
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