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參數(shù)資料
| 型號： | NX2117ACUTR |
| 廠商： | MICROSEMI CORP-ANALOG MIXED SIGNAL GROUP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, PDSO10 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-10 |
| 文件頁數(shù)： | 5/14頁 |
| 文件大?。?/td> | 405K |
| 代理商： | NX2117ACUTR |
NX2116/2116A/2116B/2117/2117A
13
Rev. 3.0
03/14/06
2
HCON
OUT
DS(ON)
2
LCON
OUT
DS(ON)
TOTAL
HCON
LCON
P
=I
DR
P
=I
(1 D) RK
P
=PP
× ××
×
××
+
K
...(20)
where the RDS(ON) will increases as MOSFET junc-
tion temperature increases, K is RDS(ON) temperature
dependency. As a result, RDS(ON) should be selected for
the worst case, in which K approximately equals to 1.4
at 125oC according to IRFR3709Z datasheet
. Conduc-
tion loss should not exceed package rating or overall
system thermal budget.
Switching loss is mainly caused by crossover con-
duction at the switching transition. The total switching
loss can be approximated.
SW
IN
OUT
SWS
1
P
V
I
TF
2
= ×
×××
...(21)
where IOUT is output current, TSW is the sum of T
R
and T
F which can be found in mosfet datasheet, and F
S
is switching frequency. Switching loss PSW is frequency
dependent.
Also MOSFET gate driver loss should be consid-
ered when choosing the proper power MOSFET.
MOSFET gate driver loss is the loss generated by dis-
charg
ing the gate capacitor and is dissipated in driver
circuits.It is proportional to frequency and is defined as:
gate
HGATE
HGS
LGATE
LGSS
P
(Q
V
Q
V
)F
=
×
+
××
...(22)
where QHGATE is the high side MOSFETs gate
charge,QLGATEis the low side MOSFETs gate charge,VHGS
is the high side gate source voltage, and V
LGS is the low
side gate source voltage.
This power dissipation should not exceed maxi-
mum power dissipation of the driver device.
Soft Start and Enable
NX2116 has digital soft start for switching control-
ler and has one enable pin for this start up. When the
Power Ready (POR) signal is high and the voltage at
enable pin is above 1.25V the internal digital counter
starts to operate and the voltage at positive input of Error
amplifier starts to increase, the feedback network will
force the output voltage follows the reference and starts
the output slowly. After 2048 cycles, the soft start is
complete and the output voltage is regulated to the de-
sired voltage decided by the feedback resistor divider.
POR
Digital
start
up
1.25V/
1.15V
+
Vbus
R1
R2
EN
10k
ON
OFF
Figure 9 - Enable and Shut down the NX2116
with Enable pin.
The start up of NX2116 can be programmed through
resistor divider at Enable pin. For example, if the input
bus voltage is12V and we want NX2116 starts when Vbus
is above 9V. We can select using the following equa-
tion.
×
=
2
1
(9V 1.25V)R
R
1.25V
The NX2116 can be turned off by pulling down the
Enable pin by extra signal MOSFET as shown in the
above Figure. When Enable pin is below 1.25V
, the digi-
tal soft start is reset to zero. In addition, all the high side
and low side driver is off and no negative spike will be
generated during the turn off.
Over Current Protection
Over current protection is achieved by sensing cur-
rent through the low side MOSFET. An internal current
source of 40uA flows through an external resistor con-
nected from OCP pin to SW node sets the over current
protection threshold. When synchronous FET is on, the
voltage at node SW is given as
SW
L
DSON
V
=-IR
×
The voltage at pin OCP is given as
OCP
SW
I
R
+V
×
When the voltage is below zero, the over current
occurss as shown in figure 10.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| NX2117CUTR | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SYNCHRONOUS PWM CONTROLLER WITH CURRENT LIMIT, POWER GOOD & OVER VOLTAGE |
| NX2119 | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SYNCHRONOUS PWM CONTROLLER WITH CURRENT LIMIT PROTECTION |
| NX2119A | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SYNCHRONOUS PWM CONTROLLER WITH CURRENT LIMIT PROTECTION |
| NX2119ACSTR | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SYNCHRONOUS PWM CONTROLLER WITH CURRENT LIMIT PROTECTION |
| NX2119ACUTR | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:SYNCHRONOUS PWM CONTROLLER WITH CURRENT LIMIT PROTECTION |
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