參數(shù)資料
型號: MAX1966
廠商: Maxim Integrated Products, Inc.
英文描述: Low-Cost Voltage-Mode PWM Step-Down Controllers
中文描述: 低成本、電壓模式、PWM降壓型控制器
文件頁數(shù): 11/15頁
文件大小: 404K
代理商: MAX1966
4) Select compensation capacitor C
6
so that the error
amp zero is equal to the complex pole frequency
LC of the inductor and output capacitor:
Input Capacitor Selection
The input capacitor (C
2
) reduces noise injection and
the current peaks drawn from the input supply. The
source impedance to the input supply determines the
value of C
2
. High source impedance requires high
input capacitance. The input capacitor must meet the
ripple current requirement (I
RMS
) imposed by the
switching currents. The RMS input ripple current is
given by:
For optimal circuit reliability, choose a capacitor that
has less than a 10
°
C temperature rise at the peak rip-
ple current.
Power MOSFET Selection
The MAX1966/MAX1967s
step-down controller drives
two external logic-level N-channel MOSFETs. The key
selection parameters are:
1) On-resistance (R
DS(ON)
) of both MOSFETs for cur-
rent limit and efficiency
2) Current capability of V
L
(MAX1967 only) and gate
charge (Q
T
)
3) Voltage rating and maximum input voltage
MOSFET Power Dissipation
Worst-case conduction losses occur at the duty factor
extremes. For the high-side MOSFET, the worst-case
power dissipation due to resistance occurs at minimum
input voltage:
The following switching loss calculation for the high-
side N-FET provides an approximation, but is no substi-
tute for evaluation:
where C
RSS
is the reverse transfer capacitance of N1
and I
GATE
is the peak gate-drive source/sink current
(1A typical). For the low-side N-FET (N2), the worst-
case power dissipation occurs at maximum input volt-
age:
The low-side MOSFET on-resistance sets the
MAX1966/MAX1967 current limit. See the
Setting the
Current Limit
section for information on selecting low-
side MOSFET R
DSON
. For designs supplying 5A or
less, it is often possible to combine the high-side and
low-side MOSFETs into a single package (usually an 8-
pin SO) as indicated in Table 1. For higher output appli-
cations, or those where efficiency is more important,
separate FETs are usually preferred.
Very-Low-Voltage Applications
The MAX1966/MAX1967 are extremely versatile con-
trollers that can be used in a variety of applications
where high efficiency, high output power, and opti-
mized cost are important. One alternate connection,
shown in Figure 5, is useful when a low-voltage supply
is to be stepped down to an even lower voltage at high
current. If an additional bias supply is available, it can
supply gate drive separately from the input power rail.
This can either improve efficiency, or allow lower cost
5V logic-level MOSFETs to be used in place of 3V
MOSFETs.
P
V
V
I
R
D N
(
OUT
VIN
LOAD
DS ON
(
)
)
×
2
1
2
=
×
P
I
I
V
f
C
D N
(
SWITCHING
LOAD
GATE
VIN MAX
(
OSC
RSS
/
)
)
1
2
=
×
×
×
P
V
V
I
R
D N RESISTIVE
(
1
OUT
VIN MIN
(
LOAD
DS ON
(
)
)
)
×
×
2
=
I
I
V
V
V
V
RMS
LOAD
OUT
VIN
OUT
VIN
=
×
×
(
)
C
L
C
R
OUT
6
3
=
×
M
Low-Cost Voltage Mode PWM
Step-Down Controller
______________________________________________________________________________________
11
Figure 5. Low Input Voltage Step-Down with Extra Bias Supply
for Gate Drive
MAX1967
V
OUT
5V TO 28V FOR
GATE BIAS
VIN
COMP/EN
GND
BST
VCC
VL
DH
LX
DL
FB
3.3V
INPUT
R2
R1
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1966ESA 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
MAX1966ESA+ 功能描述:電壓模式 PWM 控制器 Voltage-Mode PWM Step-Down RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
MAX1966ESA+T 功能描述:電壓模式 PWM 控制器 Voltage-Mode PWM Step-Down RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
MAX1966ESA-T 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
MAX1966EVKIT 功能描述:電壓模式 PWM 控制器 Evaluation Kit for the MAX1966 MAX1967 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel