參數(shù)資料
型號(hào)： MAX1980ETP
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類： 穩(wěn)壓器
英文描述： Quick-PWM Slave Controller with Driver Disable for Multiphase DC-DC Converter
中文描述： SWITCHING CONTROLLER, 550 kHz SWITCHING FREQ-MAX, PQCC20
封裝： 5 X 5 MM, 0.80 MM HEIGHT, THIN, QFN-20
文件頁數(shù)： 24/33頁
文件大?。?/td> 1153K
代理商： MAX1980ETP
M
Quick-PWM Slave Controller with
Driver Disable for Multiphase DC-DC Converter
24
______________________________________________________________________________________
If the master/slave converter is operated as the second
stage of a two-stage power-conversion system, tanta-
lum input capacitors are acceptable. In either configu-
ration, choose an input capacitor that exhibits less than
+10
°
C temperature rise at the RMS input current for
optimal circuit longevity.
Power MOSFET Selection
Most of the following MOSFET guidelines focus on the
challenge of obtaining high load-current capability
when using high-voltage (>20V) AC adapters. Low-cur-
rent applications usually require less attention.
The high-side MOSFET (N
H
) must be able to dissipate
the resistive losses plus the switching losses at both
V
IN(MIN)
and V
IN(MAX)
. Calculate both of these sums.
Ideally, the losses at V
IN(MIN)
should be roughly equal
to losses at V
IN(MAX)
, with lower losses in between. If
the losses at V
IN(MIN)
are significantly higher than the
losses at V
IN(MAX)
, consider increasing the size of N
H
.
Conversely, if the losses at V
IN(MAX)
are significantly
higher than the losses at V
IN(MIN)
, consider reducing
the size of N
H
. If V
IN
does not vary over a wide range,
the minimum power dissipation occurs where the resis-
tive losses equal the switching losses.
Choose a low-side MOSFET that has the lowest possi-
ble on-resistance (R
DS(ON)
), comes in a moderate-
sized package (i.e., one or two SO-8s, DPAK or
D
2
PAK), and is reasonably priced. Make sure that the
DL gate driver can supply sufficient current to support
the gate charge and the current injected into the para-
sitic gate-to-drain capacitor caused by the high-side
MOSFET turning on; otherwise, cross-conduction prob-
lems may occur.
MOSFET Power Dissipation
Worst-case conduction losses occur at the duty factor
extremes. For the high-side MOSFET (N
H
), the worst-
case power dissipation due to resistance occurs at the
minimum input voltage:
Generally, a small high-side MOSFET is desired to
reduce switching losses at high input voltages.
However, the R
DS(ON)
required to stay within package
power-dissipation often limits how small the MOSFET
can be. Again, the optimum occurs when the switching
losses equal the conduction (R
DS(ON)
) losses. High-
side switching losses don
’
t usually become an issue
until the input is greater than approximately 15V.
Calculating the power dissipation of the high-side
MOSFET (N
H
) due to switching losses is difficult since it
must allow for difficult quantifying factors that influence
the turn-on and turn-off times. These factors include the
internal gate resistance, gate charge, threshold volt-
age, source inductance, and PC board layout charac-
teristics. The following switching-loss calculation
provides only a very rough estimate and is no substi-
tute for breadboard evaluation, preferably including
verification using a thermocouple mounted on N
H
:
=
(
where C
RSS
is the reverse transfer capacitance of N
H
and I
GATE
is the peak gate-drive source/sink current
(1A typ).
Switching losses in the high-side MOSFET can become
an insidious heat problem when maximum AC adapter
voltages are applied, due to the squared term in the C
V
IN
MOSFET chosen for adequate R
DS(ON)
at low battery
voltages becomes extraordinarily hot when biased from
V
IN(MAX)
, consider choosing another MOSFET with
lower parasitic capacitance.
For the low-side MOSFET (N
L
), the worst-case power
dissipation always occurs at maximum input voltage:
2
SW
switching-loss equation. If the high-side
The worst case for MOSFET power dissipation occurs
under heavy overloads that are greater than I
LOAD(MAX)
but are not quite high enough to exceed the current limit
and cause the fault latch to trip. To protect against this
possibility,
“
overdesign
”
the circuit to tolerate:
where I
VALLEY(MAX)
is the maximum valley current
allowed by the current-limit circuit, including threshold
tolerance and on-resistance variation. The MOSFETs
must have a good-sized heatsink to handle the over-
load power dissipation.
Choose a Schottky diode (D1) with a forward voltage low
enough to prevent the low-side MOSFET body diode
from turning on during the dead time. As a general rule,
select a diode with a DC current rating equal to 1/(3
η
) of
the load current. This diode is optional and can be
removed if efficiency is not critical.
I
I
I
LIR
)
LOAD
VALLEY MAX
LOAD MAX
=
+
η
(
)
(
2
PD N
sistive
V
V
I
R
L
OUT
IN MAX
(
LOAD
η
DS ON
(
(
Re
)
)
)
=
1
2
PD N Switching
(
V
C
I
IN MAX
(
RSS SWLOAD
η
GATE
)
)
)
2
PD N
sistive
V
V
I
R
H
OUT
IN
LOAD
η
DS ON
(
(
Re
)
)
=
2
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1980ETP+ 功能描述:DC/DC 開關(guān)控制器 PWM Slave Controller w/Driver Disable RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
MAX1980ETP+T 功能描述:DC/DC 開關(guān)控制器 PWM Slave Controller w/Driver Disable RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
MAX1980ETP+TG075 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述:
MAX1980ETP-T 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
MAX1980ETP-TG075 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述:
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