參數(shù)資料
型號(hào)： SP6121CN
英文描述： Low Voltage, Synchronous Step Down PWM Controller Ideal for 2A to 10A, Small Footprint, DC-DC Power Converters
中文描述： 低電壓，為第2A同步降壓PWM控制器的理想下至10A，占地面積小，DC - DC電源轉(zhuǎn)換器
文件頁(yè)數(shù)： 10/16頁(yè)
文件大小： 358K
代理商： SP6121CN
Date: 5/25/04
SP6121 Low Voltage, Synchronous Step Down PWM Controller Copyright 2004 Sipex Corporation
10
supplies are connected ‘live’ to low impedance
power sources. Certain tantalum capacitors, such
as AVX TPS series, are surge tested. For ge-
neric tantalum capacitors, use 2:1 voltage derat-
ing to protect the input capacitors from surge
fall-out.
MOSFET Selection
The SP6121 drives a PMOS MOSFET on the
high side and an NMOS MOSFET synchronous
rectifier on the low side. Using a PMOS switch
on the high side negates the need for an external
charge pump and simplifies the application cir-
cuit.
The losses associated with MOSFETs can be
divided into conduction and switching losses.
Conduction losses are related to the on resis-
tance of MOSFETs, and increase with the load
current. Switching losses occur on each on/off
transition when the MOSFETs experience both
high current and voltage. Since the bottom
MOSFET switches current from/to a paralleled
diode (either its own body diode or a Schottky
diode), the voltage across the MOSFET is no
more than 1V during switching transition. As a
result, its switching losses are negligible. The
switching losses are difficult to quantify due to
all the variables affecting turn on/off time. How-
ever, making the assumption that the turn on and
turn off transition times are equal, the transition
time can be approximated by:
t
T
= C
ISS
V
IN
,
I
G
where;
C
ISS
is the PMOS’s input capacitance, or the
sum of the gate-to-source capacitance, C
GS
, and
the drain-to-gate capacitance, C
GD
. This param-
eter can be directly obtained from the MOSFET’s
data sheet I
G
is the gate drive current provided
by the SP6121 (approximately 1A at V
IN
=5V)
and V
IN
is the input supply voltage.
Therefore an approximate expression for the
switching losses associated with the high side
MOSFET can be given as:
P
SH(max)
= (V
IN(max)
+ V
F
)I
OUT(max)
t
T
F
S
,
where;
t
T
= the switching transition time
V
F
= free wheeling diode drop
Switching losses need to be taken into account
for high switching frequency, since they are
directly proportional to switching frequency.
The conduction losses associated with top and
bottom MOSFETs are determined by
P
CH(max)
= R
DS(ON)
I
OUT(max)
2
D
P
CL(max)
= R
DS(ON)
I
OUT(max)
where;
P
CH(max)
= conduction losses of the high side
MOSFET
P
CL(max)
= conduction losses of the low side
MOSFET
R
DS(ON)
= drain to source on resistance.
2
(1 - D),
The total power losses of the top MOSFET are
the sum of switching and conduction losses. For
synchronous buck converters of efficiency over
90%, allow no more than 4% power losses for
high or low side MOSFETs. For input voltages
of 3.3V and 5V, conduction losses often domi-
nate switching losses. Therefore, lowering the
R
DS(ON)
of the MOSFETs always improves
efficiency even though it gives rise to higher
switching losses due to increased C
ISS
.
Total gate charge is the charge required to turn
the MOSFETs on and off under the specified
operating conditions (V
GS
and V
DS
). The gate
charge is provided by the SP6121 gate drive
circuitry. (At 500kHz switching frequency, the
gate charge is the dominant source of power
dissipation in the SP6121.) At low output levels,
this power dissipation is noticeable as a reduc-
tion in efficiency. The average current required
to drive the high side and low side MOSFETs is:
I
G(av)
= Q
GH
F
S
+ Q
GL
F
S
,
where;
Q
GH
= gate charge of PMOS
Q
GL
= gate charge of NMOS
Considering that the gate charge current comes
from the input supply voltage VIN, the power
dissipated in the SP6121 due to the gate drive is:
P
GATE DRIVE
= V
IN
I
G(av)
R
DS(ON)
varies greatly with the gate driver volt-
age. The MOSFET vendors often specify R
DS(ON)
on multiple gate to source voltages (V
GS
), as
APPLICATIONS INFORMATION: Continued
相關(guān)PDF資料
PDF描述
SP6121EB Demo Board Manual
SP6132H High Voltage, 300KHz Synchronous PWM Controller
SP6132HEU High Voltage, 300KHz Synchronous PWM Controller
SP6134 Dual Supply Synchronous Buck Controller
SP6134CU Dual Supply Synchronous Buck Controller
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
SP6121CN/TR 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 Low Voltage, 8 Pin Synchronous, Cntrllr RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel
SP6121CN-L 功能描述:電壓模式 PWM 控制器 Low Voltage, 8 Pin Synchronous, Cntrllr 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
SP6121CN-L/TR 功能描述:電壓模式 PWM 控制器 Low Voltage, 8 Pin Synchronous, Cntrllr 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
SP6121EB 功能描述:電壓模式 PWM 控制器 Low Voltage, 8 Pin Sync Buck Controller 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
SP6122 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*