參數(shù)資料
型號(hào): LTC3766MPUFD#PBF
廠商: LINEAR TECHNOLOGY CORP
元件分類(lèi): 穩(wěn)壓器
英文描述: SWITCHING CONTROLLER, 316 kHz SWITCHING FREQ-MAX, PQCC28
封裝: 4 X 5 MM, LEAD FREE, PLASTIC, MO-220, QFN-28
文件頁(yè)數(shù): 32/60頁(yè)
文件大?。?/td> 607K
代理商: LTC3766MPUFD#PBF
LTC3766
38
3766f
APPLICATIONS INFORMATION
When calculating tOUT, use a value for VHO that corre-
sponds to the target output voltage for control hand-off,
typicallyone-halfthenormalregulationlevelorless.IftOUT
is less than tBIAS, then the LTC3765 soft-start capacitor
value should be increased. Note that these equations are
approximations and the actual times will vary somewhat
with circuit parameters.
Peak Charge Bias Configurations
When the peak voltage on the SW node is in the range of
7V to 32V, the peak charge can be taken directly from the
SW node as shown in Figure 20. In practice, this condi-
tion only holds when the output voltage of the converter
is approximately 5V.
In most applications, it is necessary to add an additional
auxiliarywindingonthesecondaryforuseingeneratingan
adequate bias voltage. For low VOUT applications (VOUT <
5V), this winding can be configured as shown in Figure21
to provide a higher voltage for bias generation.
This configuration is advantageous because it achieves
a higher voltage on the transformer secondary with a
minimumnumberofadditionalturns.Thenumberofturns
on the auxiliary winding for this configuration should be
approximately:
NAUX ≈NS
VB(MIN)DMAX
VOUT
– 1
whereDMAXisthemaximumoperatingdutycycle(typically
0.65 to 0.70) and VB(MIN) is either 7V for low voltage or
10V for high voltage drive mode operation. These values
for VB(MIN) are approximately 2V higher than the UVLO
levels on the LTC3766 to allow for drops in the peak charge
circuit. As an example, for VOUT = 1.5V, DMAX = 0.65V and
NS = 1 turn, use NAUX = 2 turns, assuming low voltage
drive mode.
For high VOUT applications (VOUT > 6V), this winding can
be configured as shown in Figure 22 to provide a reduced
voltageforgeneratingbias.Inthiscase,chooseanauxiliary
winding with turns
NAUX ≈NS
VB(MIN)DMAX
VOUT
VIN
RPK
DPK
SW
NS
NP
CVCC
3766 F20
NDRV
LTC3766
MAIN
XFMR
VBIAS = 6V TO 32V
VCC
CPK
Q1
Figure 20. Peak Charge Directly from SW for VOUT ≈ 5V
VIN
RPK
DPK
NS
NAUX
SW
NP
CVCC
3766 F21
NDRV
LTC3766
MAIN
XFMR
VBIAS = 6V TO 32V
VCC
CPK
Q1
Figure 21. Peak Charge for Low VOUT Applications
VIN
RPK
DPK
NS
NAUX
SW
NP
CVCC
3766 F22
NDRV
LTC3766
MAIN
XFMR
VBIAS = 6V TO 32V
VCC
CPK
Q1
Figure 22. Peak Charge for High VOUT Applications
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