参数资料
| 型号： | SP6125EK1-L/TR |
| 厂商： | Exar Corporation |
| 文件页数： | 7/12页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 6TSOT |
| 标准包装： | 2,500 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 345kHz |
| 占空比： | 100% |
| 电源电压： | 4.5 V ~ 29 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | SOT-23-6 细型，TSOT-23-6 |
| 包装： | 带卷 (TR) |
General Overview
Power MOSFET Selection
where:
Vf is diode forward voltage at I OUT
Select the Power MOSFET for Voltage rating
L = ( Vin ? Vout ) × ?
? × ? ?
? ? × ? ?
? ?
RDS ( ON ) ≤ ?
Pcond = Iout × RDS ( ON ) × ?
? Vout ?
BV DSS , On resistance R DS(ON) , and thermal
resistance Rthja. BV DSS should be about twice
as high as V IN in order to guard against
switching transients. Recommended MOSFET
voltage rating for V IN of 5V, 12V and 24V is
12V, 30V and 40V respectively. R DS(ON) , must
be selected such that when operating at peak
current and junction temperature the
Overcurrent threshold of the SP6125 is not
exceeded. Allowing 50% for temperature
coefficient of R DS(ON) and 15% for inductor
current ripple, the following expression can be
used:
? 300 mV ?
?
? 1 . 5 × 1 . 15 × Iout ?
Within this constraint, selecting MOSFETs with
lower R DS(ON) will reduce conduction losses at
the expense of increased switching losses. As
a rule of thumb select the highest R DS(ON)
MOSFET that meets the above criteria.
Switching losses can be assumed to roughly
equal the conduction losses. A simplified
expression for conduction losses is given by:
?
? Vin ?
Schottky’s AC losses due to its switching
capacitance are negligible.
Inductor Selection
Select the Inductor for inductance L and
saturation current Isat. Select an inductor with
Isat higher than the programmed overcurrent.
Calculate inductance from:
? Vout ? ? 1 ? ? 1 ?
? Vin ? ? f ? ? Irip ?
where:
V IN is converter input voltage
V OUT is converter output voltage
f is switching frequency
I RIP is inductor peak-to-peak current ripple
(nominally set to 30% of I OUT )
Keep in mind that a higher I RIP results in a
smaller inductor which has the advantages of
small size, low DC equivalent resistance DCR,
high saturation current Isat and allows the use
of a lower output capacitance to meet a given
step load transient. A higher Irip, however,
increases the output voltage ripple and
MOSFET’s junction
estimated from:
temperature
can
be
increases the current at which converter enters
Discontinuous Conduction Mode. The output
current at which converter enters DCM is ? of
T = ( 2 × Pc × Rthja ) + Tambient
Schottky Rectifier selection
I RIP . Note that a negative current step load that
drives the converter into DCM will result in a
large output voltage transient. Therefore the
lowest current for a step load should be larger
than ? of I RIP .
Select the Schottky for Voltage rating V R ,
Forward voltage V f , and thermal resistance
Rthja. Voltage rating should be selected using
the same guidelines outlined for MOSFET
voltage selection. For a low duty cycle
application such as the circuit shown on first
page, the Schottky is conducting most of the
time and its conduction losses are the largest
component of losses in the converter.
Conduction losses can be estimated from:
Output Capacitor Selection
Select the output capacitor for voltage rating,
capacitance and Equivalent Series Resistance
(ESR). Nominally the voltage rating is selected
to be twice as large as the output voltage.
Select the capacitance to satisfy the
specification for output voltage overshoot or
undershoot caused by current step load. A
Pc = Vf × Iout × ? 1 ?
Vout ?
inductor stored energy of ? L I OUT . A sudden
?
?
?
Vin ?
steady-state output current I OUT corresponds to
2
decrease in I OUT forces the energy surplus in L
to be absorbed by C OUT .
Jan28-08 RevG
SP6125: TSOT-6 PFET Buck Controller
7
? 2007 Exar Corporation
相关PDF资料 |
PDF描述 |
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| SP6126EK1-L | IC REG CTRLR BUCK PWM VM 6TSOT |
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相关代理商/技术参数 |
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| SP6126_07 | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:High-Voltage, Step Down Controller in TSOT6 |
| SP6126_1 | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP6126EB | 功能描述:电源管理IC开发工具 Eval Board for SP6126 Series RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| SP6126EK1 | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Evaluation Board Manual |
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