LT8301MP 查看數據表（PDF） - Analog Devices

零件编号

产品描述 (功能)

比赛名单

LT8301MP

42VIN Micropower No-Opto Isolated Flyback Converter with 65V/1.2A Switch

Analog Devices 

LT8301

APPLICATIONS INFORMATION

Tables 2 and 3 show some recommended diodes and

Zener diodes.

Table 2. Recommended Zener Diodes

PART

VZENER POWER

(V)

(W)

CASE

CMDZ5248B 18

0.25 SOD-323

CMDZ5250B 20

0.25 SOD-323

VENDOR

Central Semiconductor

Table 3. Recommended Diodes

PART

IMAX VREVERSE

(A) (V)

CASE

VENDOR

CMHD4448 0.25 100 SOD-123 Central Semiconductor

DFLS1100

1

100 PowerDI-123 Diodes Inc.

DFLS1150

1

150 PowerDI-123 Diodes Inc.

The recommended approach for designing an RC snub-

ber is to measure the period of the ringing on the SW

pin when the power switch turns off without the snub-

ber and then add capacitance (starting with 100pF) until

the period of the ringing is 1.5 to 2 times longer. The

change in period will determine the value of the parasitic

capacitance, from which the parasitic inductance can be

determined from the initial period, as well. Once the value

of the SW node capacitance and inductance is known, a

series resistor can be added to the snubber capacitance

to dissipate power and critically dampen the ringing. The

equation for deriving the optimal series resistance using

the observed periods ( tPERIOD and tPERIOD(SNUBBED)) and

snubber capacitance (CSNUBBER) is:

CPAR

=

⎛

⎝⎜

CSNUBBER

tPERIOD(SNUBBED)

tPERIOD

⎞

⎠⎟

2

−

1

L

PAR

=

tPERIOD2

CPAR • 4π2

RSNUBBER =

LPAR

CPAR

Note that energy absorbed by the RC snubber will be

converted to heat and will not be delivered to the load.

In high voltage or high current applications, the snubber

may need to be sized for thermal dissipation.

Undervoltage Lockout (UVLO)

A resistive divider from VIN to the EN/UVLO pin imple-

ments undervoltage lockout (UVLO). The EN/UVLO pin

falling threshold is set at 1.228V with 14mV hysteresis.

In addition, the EN/UVLO pin sinks 2.5µA when the volt-

age at the pin is below 1.228V. This current provides user

programmable hysteresis based on the value of R1. The

programmable UVLO thresholds are:

VIN(UVLO+)

=

1.242V •(R1+

R2

R2)

+

2.5µA

•

R1

VIN(UVLO−)

=

1.228V •(R1+

R2

R2)

Figure 7 shows the implementation of external shutdown

control while still using the UVLO function. The NMOS

grounds the EN/UVLO pin when turned on, and puts the

LT8301 in shutdown with quiescent current less than 2µA.

VIN

R1

EN/UVLO

LT8301

R2

GND

8301 F07

RUN/STOP

CONTROL

(OPTIONAL)

Figure 7. Undervoltage Lockout (UVLO)

Rev. B

14

For more information www.analog.com

Share Link: