参数资料
型号: LTC3828EUH#TRPBF
厂商: Linear Technology
文件页数: 24/32页
文件大小: 0K
描述: IC REG CTRLR BUCK PWM CM 32-QFN
标准包装: 2,500
系列: PolyPhase®
PWM 型: 电流模式
输出数: 2
频率 - 最大: 590kHz
占空比: 99.4%
电源电压: 4.5 V ~ 28 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: -40°C ~ 85°C
封装/外壳: 32-WFQFN 裸露焊盘
包装: 带卷 (TR)
LTC3828
APPLICATIONS INFORMATION
during load-dump. Note that the transient suppressor
should not conduct during double-battery operation, but
must still clamp the input voltage below breakdown of the
converter. Although the LTC3828 have a maximum input
occurs at the maximum input voltage. Tie the PLLFLTR
pin to a resistive divider from the INTV CC pin, generating
0.7V for 300kHz operation. The minimum inductance for
30% ripple current is:
( f )( L ) ?
V IN ?
voltage of 30V, most applications will also be limited to
30V by the MOSFET BVD SS .
Δ I L =
V OUT ?
? 1 –
V OUT ?
?
50A I PK RATING
12V
TRANSIENT VOLTAGE
SUPPRESSOR
GENERAL INSTRUMENT
1.5KA24A
V IN
LTC3828
A 4.7μH inductor will produce 23% ripple current and a
3.3μH will result in 33%. The peak inductor current will
be the maximum DC value plus one half the ripple cur-
rent, or 5.84A, for the 3.3μH value. Increasing the ripple
current will also help ensure that the minimum on-time
3828 F11a
Figure 11a. Automotive Application Protection
of 100ns is not violated. The minimum on-time occurs at
maximum V IN :
For applications where the main input power is 5V, tie the
V IN , INTV CC and DRV CC pins together and tie the combined
t ON ( MIN ) =
V OUT
V IN ( MAX ) f
=
1 . 8 V
22 V ( 300 kHz )
= 273 ns
R SENSE ≤
≈ 0 . 01 Ω
R VIN
R 1 MAX ) = 24 k ? ?
= 24 k ? ? = 32 k
pinstothe5Vinputwitha1Ωor2.2Ωresistorasshown
in Figure 11b to minimize the voltage drop caused by the
gate charge current. This will override the INTV CC regula-
tor and will prevent INTV CC from dropping too low due to
the dropout voltage. Make sure the INTV CC voltage is at
or exceeds the R DS(ON) test voltage for the MOSFET which
is typically 4.5V for logic-level devices.
V IN
LTC3828
INTV CC 5V
C INTVCC +
4.7μF C IN
DRV CC *
3828 F11b
*LTC3828EUH ONLY
Figure 11b. Setup for a 5V Input
Design Example
As a design example for one channel, assume V IN =
12V(nominal), V IN = 22V(max), V OUT = 1.8V, I MAX = 5A
and f = 300kHz.
The inductance value is chosen ?rst based on a 30% ripple
current assumption. The highest value of ripple current
The R SENSE resistor value can be calculated by using the
maximum current sense voltage speci?cation with some
accommodation for tolerances:
60mV
5 . 84 A
Since the output voltage is below 2.4V the output resis-
tive divider will need to be sized to not only set the output
voltage but also to absorb the SENSE pin’s speci?ed input
current.
? 0 . 8 V ?
? 2 . 4 V – V OUT ?
? 0 . 8 V ?
? 2 . 4 V – 1 . 8 V ?
Choosing 1% resistors: R1 = 25.5k and R2 = 32.4k yields
an output voltage of 1.816V.
The power dissipation on the topside MOSFET can be easily
estimated. Choosing a Fairchild FDS6982S dual MOSFET
results in: R DS(ON) = 0.035Ω/0.022Ω, C MILLER = 215pF. At
maximum input voltage with T(estimated) = 50°C:
3828fc
24
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