参数资料
型号: LT3748EMS#PBF
厂商: Linear Technology
文件页数: 19/30页
文件大小: 0K
描述: IC REG CTRLR FLYBK ISO CM 16MSOP
产品培训模块: LT3748 100V Flyback Controller
特色产品: LT3748 Isolated Flyback Controller
标准包装: 37
PWM 型: 电流模式
输出数: 1
电源电压: 5 V ~ 100 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: -40°C ~ 125°C
封装/外壳: 16-TFSOP(0.118",3.00mm),12 引线
包装: 管件
配用: 732-3308-ND - BOARD EVAL FOR LT3748
732-3305-ND - BOARD EVAL FOR LT3748
相关产品: 732-2669-2-ND - TRANS FLYBACK LT3748 20UH SMD
732-2669-6-ND - TRANS FLYBACK LT3748 20UH SMD
732-2668-6-ND - TRANS FLYBACK LT3748 14UH SMD
732-2667-6-ND - TRANS FLYBACK LT3748 500UH SMD
732-2666-6-ND - TRANS FLYBACK LT3748 12UH SMD
732-2665-6-ND - TRANS FLYBACK LT3748 12UH SMD
732-2664-6-ND - TRANS FLYBACK LT3748 15UH SMD
732-2663-6-ND - TRANS FLYBACK LT3748 15UH SMD
732-2662-6-ND - TRANS FLYBACK LT3748 8UH SMD
732-2661-6-ND - TRANS FLYBACK LT3748 8UH SMD
更多...
LT3748
APPLICATIONS INFORMATION
LT3748
V IN
5V TO 100V
3.0
V IN = 5V
2.5
LDO
INTV CC
(V IN – DROPOUT) TO 7V
2.0
1.5
1.0
INTV CC UVLO = 3.6V
I INTVCC = 20mA
LT3748
V IN
5V TO 20V
0.5
LDO
0
–50 –25
0
25
50
75
100 125 150
TEMPERATURE ( C)
3748 F12
INTV CC
OPTIONAL
Figure 12. INTV CC Current at Low V IN Can Cause the LT3748 to
Stop Switching Due to INTV CC Undervoltage Lockout
LT3748
V IN
5V TO 100V
and I INTVCC = 20mA might be fully functional at room
temperature, but when the dropout for the same current
exceeds 1.4V and trips the UVLO at higher temperatures
LDO
3.6V < BIAS < 20V,
the LT3748 will stop switching.
INTV CC
V IN > BIAS
EXTERNAL SUPPLY
OR THIRD WINDING
Overdriving INTV CC with a Third Winding
3748 F09
Figure 11. INTV CC Pin Configurations
selected MOSFET switch at the expected V IN and INTV CC
voltages and multiply that charge required with each
turn-on event by the maximum operating frequency. The
maximum operating frequency in a given application can
be approximated from the primary transformer inductance,
the windings ratio (N PS ), the nominal output voltage and
the maximum input voltage. Unless the part is limited by
minimum on- or off-times, this maximum frequency will
occur when the part is regulating in boundary mode at the
minimum peak switch current, and can be derived from:
The LT3748 provides excellent output voltage regulation
without the need for an opto-coupler or third winding,
but for some applications with input voltages greater than
20V, an additional winding may improve overall system
efficiency. The third winding should be designed to out-
put a voltage between 7.2V and 20V. For a typical 48V IN ,
10W application, overdriving the INTV CC pin may improve
efficiency by several percent at maximum load and as
much as 30% at light loads.
Loop Compensation
The LT3748 is compensated using an external resistor-
capacitor network on the V C pin. Typical values are in the
f SW(MAX) ≈
L PRI ? I LIM(MIN) ? ( V OUT + V F(DIODE) ? N PS + V IN(MAX)
V IN(MAX) ? ( V OUT + V F(DIODE) ) ? N PS
)
range of R C = 50k and C C = 1nF (see the numerous sche-
matics in the Typical Applications section for other possible
values). If too large of an R C value is used, the part will be
more susceptible to high frequency noise and jitter. If too
With the maximum INTV CC current calculated, the expected
dropout when V IN drops below 7V can be extracted from
the curves in the Typical Performance Characteristics sec-
tion. The LT3748 is tested as low as V IN = 5V but the hard
limit on minimum V IN operation is the INTV CC regulator
dropout and the 3.6V under voltage lockout. Figure 12
illustrates an example where operation with V IN = 5V
small of an R C value is used, the transient performance will
suffer. The value choice for C C is somewhat the inverse
of the R C choice: if too small a C C value is used, the loop
may be unstable and if too large a C C value is used, the
transient performance will also suffer. Transient response
plays an important role for any DC/DC converter.
3748fa
19
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LT3748HMSPBF 制造商:LINER 制造商全称:Linear Technology 功能描述:100V Isolated Flyback Controller
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