參數(shù)資料
型號： LTC3780
廠商： Linear Technology Corporation
英文描述： DIODE SCHOTTKY DUAL ISOLATED 25V 150mW 0.33V-vf 200mA-IFM 2mA-IF 0.5uA-IR SOT-563 3K/REEL
中文描述： 高效率，同步，四開關(guān)降壓升壓控制器
文件頁數(shù)： 19/28頁
文件大?。?/td> 421K
代理商： LTC3780
19
LTC3780
3780f
APPLICATIU
The R
TH(JA)
to be used in the equation normally includes
the R
TH(JC)
for the device plus the thermal resistance from
the case to the ambient temperature (R
TH(JC)
). This value
of T
J
can then be compared to the original, assumed value
used in the iterative calculation process.
W
U
U
Schottky Diode (D1, D2) Selection
and Light Load Operation
The Schottky diodes D1 and D2 shown in Figure 1 conduct
during the dead time between the conduction of the power
MOSFET switches. They are intended to prevent the body
diode of Synchronous Switches B and D from turning on
and storing charge during the dead time. In particular, D2
significantly reduces reverse recovery current between
Switch D turn-off and Switch C turn-on, which improves
converter efficiency and reduces Switch C voltage stress.
In order for the diode to be effective, the inductance
between it and the synchronous switch must be as small
as possible, mandating that these components be placed
adjacently.
In Buck mode, when the FCB pin voltage is 0.85 < V
FCB
<
5V, the converter operates in Skip-Cycle mode. In this
mode, Synchronous Switch B remains off until the induc-
tor peak current exceeds one-fifth of its maximum peak
current. As a result, D1 should be rated for about one-half
to one-third of the full load current.
In Boost mode, when the FCB pin voltage is higher than
5.3V, the converter operates in Discontinuous Current
mode. In this mode, Synchronous Switch D remains off
until the inductor peak current exceeds one-fifth of its
maximum peak current. As a result, D2 should be rated for
about one-third to one-fourth of the full load current.
In Buck mode, when the FCB pin voltage is higher than
5.3V, the converter operates in constant frequency Dis-
continuous Current mode. In this mode, Synchronous
Switch B remains on until the inductor valley current is
lower than the sense voltage representing the minimum
negative inductor current level (V
SENSE
= –5mV). Both
Switch A and B are off until next clock signal.
In Boost mode, when the FCB pin voltage is 0.85 < V
FCB
<
5.3V, the converter operates in Burst Mode operation. In
this mode, the controller clamps the peak inductor current
to approximately 20% of the maximum inductor current.
The output voltage ripple can increase during Burst Mode
operation.
INTV
CC
Regulator
An internal P-channel low dropout regulator produces 6V
at the INTV
CC
pin from the V
IN
supply pin. INTV
CC
powers
the drivers and internal circuitry within the LTC3780. The
INTV
CC
pin regulator can supply a peak current of 40mA
and must be bypassed to ground with a minimum of 4.7
μ
F
tantalum, 10
μ
F special polymer or low ESR type electro-
lytic capacitor. A 1
μ
F ceramic capacitor placed directly
adjacent to the INTV
CC
and PGND IC pins is highly
recommended. Good bypassing is necessary to supply
the high transient current required by MOSFET gate
drivers.
Higher input voltage applications in which large MOSFETs
are being driven at high frequencies may cause the
maximum junction temperature rating for the LTC3780 to
be exceeded. The system supply current is normally
dominated by the gate charge current. Additional external
loading of the INTV
CC
also needs to be taken into account
for the power dissipation calculations. The total INTV
CC
current can be supplied by either the 6V internal linear
regulator or by the EXTV
CC
input pin. When the voltage
applied to the EXTV
CC
pin is less than 5.7V, all of the
INTV
CC
current is supplied by the internal 6V linear
regulator. Power dissipation for the IC in this case is
V
IN
I
INTVCC
, and overall efficiency is lowered. The junc-
tion temperature can be estimated by using the equations
given in Note 2 of the Electrical Characteristics. For
example, LTC3780 V
IN
current is limited to less than
24mA from a 24V supply when not using the EXTV
CC
pin
as:
T
J
= 70
°
C + 24mV 24V 95
°
C/W = 125
°
C
Use of the EXTV
CC
input pin reduces the junction tempera-
ture to:
T
J
= 70
°
C + 24mV 6V 95
°
C/W = 84
°
C
To prevent maximum junction temperature from being
exceeded, the input supply current must be checked
operating in continuous mode at maximum V
IN
.
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參數(shù)描述
LTC3780EG 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 24-Pin SSOP
LTC3780EG#PBF 功能描述:IC REG CTRLR BST PWM CM 24-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標準包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR
LTC3780EG#TR 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 24-Pin SSOP T/R
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