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| 型號： | ISL6244CR-T |
| 廠商： | INTERSIL CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Multi-Phase PWM Controller |
| 中文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC32 |
| 封裝： | 5 X 5 MM, ROHS COMPLIANT, PLASTIC, MO-220VHHD-2, QFN-32 |
| 文件頁數(shù)： | 18/25頁 |
| 文件大?。?/td> | 845K |
| 代理商： | ISL6244CR-T |
18
FN9106.3
December 28, 2004
UPPER MOSFET POWER CALCULATION
In addition to r
DS(ON)
losses, a large portion of the upper-
MOSFET losses are due to currents conducted across the
input voltage (V
IN
) during switching. Since a substantially
higher portion of the upper-MOSFET losses are dependent
on switching frequency, the power calculation is more
complex. Upper MOSFET losses can be divided into
separate components involving the upper-MOSFET
switching times; the lower-MOSFET body-diode reverse-
recovery charge, Q
rr
; and the upper MOSFET r
DS(ON)
conduction loss.
When the upper MOSFET turns off, the lower MOSFET does
not conduct any portion of the inductor current until the
voltage at the phase node falls below ground. Once the
lower MOSFET begins conducting, the current in the upper
MOSFET falls to zero as the current in the lower MOSFET
ramps up to assume the full inductor current. In Equation 16,
the required time for this commutation is t
1
and the
approximated associated power loss is P
UP,1
.
The upper MOSFET begins to conduct and this transition
occurs over a time t
2
. In Equation 17, the approximate power
loss is P
UP,2
.
A third component involves the lower MOSFET’s reverse-
recovery charge, Q
rr
. Since the inductor current has fully
commutated to the upper MOSFET before the lower-
MOSFET’s body diode can draw all of Q
rr
, it is conducted
through the upper MOSFET across VIN. The power
dissipated as a result is P
UP,3
and is approximately
Finally, the resistive part of the upper MOSFET’s is given in
Equation 19 as P
UP,4
.
In this case, of course, r
DS(ON)
is the on resistance of the
upper MOSFET.
The total power dissipated by the upper MOSFET at full load
can now be approximated as the summation of the results
from Equations 16, 17, 18 and 19. Since the power
equations depend on MOSFET parameters, choosing the
correct MOSFETs can be an iterative process that involves
repetitively solving the loss equations for different MOSFETs
and different switching frequencies until converging upon the
best solution.
Current Sensing
The ISEN pins are denoted ISEN1, ISEN2, ISEN3 and
ISEN4. The resistors connected between these pins and
their respective phase nodes determine the gains in the
load-line regulation loop and the channel-current balance
loop. Select the values for these resistors based on the room
temperature r
DS(ON)
of the lower MOSFETs; the full-load
operating current, I
FL
; and the number of phases, N
according to Equation 20 (see also Figure 15).
In certain circumstances, it may be necessary to adjust the
value of one or more of the ISEN resistors. This can arise
when the components of one or more channels are inhibited
from dissipating their heat so that the affected channels run
hotter than desired (see the section entitled
Channel-Current
Balance
). In these cases, chose new, smaller values of R
ISEN
for the affected phases. Choose R
ISEN,2
in proportion to the
desired decrease in temperature rise in order to cause
proportionally less current to flow in the hotter phase.
In Equation 21, make sure that
T
2
is the desired temperature
rise above the ambient temperature, and
T
1
is the measured
temperature rise above the ambient temperature. While a
single adjustment according to Equation 21 is usually
sufficient, it may occasionally be necessary to adjust R
ISEN
two or more times to achieve perfect thermal balance
between all channels.
Load-Line Regulation Resistor
The load-line regulation resistor is labeled R
FB
in Figure
17. Its value depends on the desired full-load droop voltage
(V
DROOP
in Figure 17). If Equation 20 is used to select
each ISEN resistor, the load-line regulation resistor is as
shown in Equation 22.
V
6
–
If one or more of the ISEN resistors was adjusted for thermal
balance, as in Equation 21, the load-line regulation resistor
should be selected according to Equation 23. Where I
FL
is
the full-load operating current and R
ISEN(n)
is the ISEN
resistor connected to the n
th
ISEN pin.
V
FL
r
DS ON
)
Compensation
The two opposing goals of compensating the voltage
regulator are stability and speed. Depending on whether the
regulator employs the optional load-line regulation as
described in Load-Line Regulation, there are two distinct
methods for achieving these goals.
P
UP 1
V
IN
I
M
N
-----
I
---2
+
t
1
2
----
f
S
≈
(EQ. 16)
P
UP 2
,
V
IN
I
M
N
-----
I
---2
–
t
2
2
----
f
S
≈
(EQ. 17)
P
UP 3
V
IN
Q
rr
f
S
=
(EQ. 18)
P
UP 4
r
DS ON
)
I
M
N
-----
2
d
I
2
--12
+
≈
(EQ. 19)
R
ISEN
r
50 10
6
)
–
-----------------------
I
--N
=
(EQ. 20)
R
ISEN 2
R
ISEN
T
2
T
1
----------
=
(EQ. 21)
R
FB
50 10
------------------------
=
(EQ. 22)
R
FB
I
R
ISEN n
( )
n
∑
=
(EQ. 23)
ISL6244
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ISL6244CRZ | 功能描述:電流型 PWM 控制器 VER OF ISL6244CR RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| ISL6244CRZ-T | 功能描述:電流型 PWM 控制器 VER OF ISL6244CR-T RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| ISL6244EVAL1 | 功能描述:EVALUATION BOARD ISL6244 RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - DC/DC 與 AC/DC（離線）SMPS 系列:- 產(chǎn)品培訓模塊:Obsolescence Mitigation Program 標準包裝:1 系列:True Shutdown™ 主要目的:DC/DC，步升 輸出及類型:1，非隔離 功率 - 輸出:- 輸出電壓:- 電流 - 輸出:1A 輸入電壓:2.5 V ~ 5.5 V 穩(wěn)壓器拓撲結(jié)構(gòu):升壓 頻率 - 開關:3MHz 板類型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| ISL6244HR | 功能描述:IC REG CTRLR BUCK PWM 32-QFN RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 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:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| ISL6244HR-T | 功能描述:IC REG CTRLR BUCK PWM 32-QFN RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 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:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
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