LT8302MPS8E 查看數據表（PDF） - Linear Technology
零件编号
产品描述 (功能)
比赛名单
LT8302MPS8E
Linear Technology
LT8302MPS8E Datasheet PDF : 26 Pages
| |||
LT8302
Applications Information
The equations below calculate output power:
POUT = η • VIN • D • ISW(MAX) • 0.5
η = Efficiency = ~85%
( ( ) ) D = Duty Cycle =
VOUT + VF •NPS
VOUT + VF •NPS + VIN
ISW(MAX) = Maximum switch current limit = 3.6A (MIN)
Primary Inductance Requirement
The LT8302 obtains output voltage information from the
reflected output voltage on the SW pin. The conduction
of secondary current reflects the output voltage on the
primary SW pin. The sample-and-hold error amplifier needs
a minimum 350ns to settle and sample the reflected output
voltage. In order to ensure proper sampling, the second-
ary winding needs to conduct current for a minimum of
350ns. The following equation gives the minimum value
for primary-side magnetizing inductance:
( ) LPRI
≥
tOFF(MIN)
•NPS • VOUT
ISW(MIN)
+
VF
tOFF(MIN) = Minimum switch-off time = 350ns (TYP)
ISW(MIN) = Minimum switch current limit = 0.87A (TYP)
In addition to the primary inductance requirement for
the minimum switch-off time, the LT8302 has minimum
switch-on time that prevents the chip from turning on
the power switch shorter than approximately 160ns. This
minimum switch-on time is mainly for leading-edge blank-
ing the initial switch turn-on current spike. If the inductor
current exceeds the desired current limit during that time,
oscillation may occur at the output as the current control
loop will lose its ability to regulate. Therefore, the following
equation relating to maximum input voltage must also be
followed in selecting primary-side magnetizing inductance:
LPRI
≥
tON(MIN) • VIN(MAX)
ISW(MIN)
tON(MIN) = Minimum switch-on time = 160ns (TYP)
In general, choose a transformer with its primary mag-
netizing inductance about 40% to 60% larger than the
minimum values calculated above. A transformer with
much larger inductance will have a bigger physical size
and may cause instability at light load.
Selecting a Transformer
Transformer specification and design is perhaps the most
critical part of successfully applying the LT8302. In addition
to the usual list of guidelines dealing with high frequency
isolated power supply transformer design, the following
information should be carefully considered.
Linear Technology has worked with several leading mag-
netic component manufacturers to produce pre-designed
flyback transformers for use with the LT8302. Table 1
shows the details of these transformers.
Table 1. Predesigned Transformers–Typical Specifications
TRANSFORMER
PART NUMBER
DIMENSIONS
(W × L × H) (mm)
LPRI LLKG
(µH) (µH) NP:NS
750311625
17.75 × 13.46 × 12.70 9 0.35 4:1
750311564
17.75 × 13.46 × 12.70 9 0.12 3:1
750313441
15.24 × 13.34 x 11.43 9
0.6 2:1
750311624
17.75 × 13.46 × 12.70 9 0.18 3:2
750313443
15.24 × 13.34 × 11.43 9
0.3 1:1:1
750313445
15.24 × 13.34 × 11.43 9 0.25 1:2
750313457
15.24 × 13.34 × 11.43 9 0.25 1:4
750313460
15.24 × 13.34 × 11.43 12 0.7 4:1
750311342
15.24 × 13.34 × 11.43 15 0.44 2:1
750313439
15.24 × 13.34 × 11.43 12 0.6 2:1
750313442
15.24 × 13.34 × 11.43 12 0.75 3:2
RPRI
(mΩ)
43
36
75
34
85
85
85
85
85
115
150
RSEC
(mΩ)
6
7
18
21
100
190
770
11
22
28
53
VENDOR
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
Würth Elektronik
TARGET APPLICATION
VIN (V)
8 to 32
VOUT (V)
3.3
IOUT (A)
2.1
8 to 32
5
1.5
8 to 32
5
1.3
8 to 32
8
0.9
8 to 36
±12
0.3
8 to 36
24
0.3
8 to 36
48
0.15
4 to 18
5
0.9
4 to 18
12
0.4
18 to 42
3.3
2.1
18 to 42
5
1.6
8302fa
14
For more information www.linear.com/LT8302
Share Link: