参数资料
| 型号： | SP6121CN-L |
| 厂商： | Exar Corporation |
| 文件页数： | 12/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 8NSOIC |
| 标准包装： | 98 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 560kHz |
| 占空比： | 100% |
| 电源电压： | 3 V ~ 5.5 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： | 0°C ~ 70°C |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
APPLICATIONS INFORMATION
associated with the output capacitors and can be
determined by
To fine-tune the compensation, it is necessary to
physically measure the frequency response us-
ing a network analyzer.
f Z(ESR) =
1
2 π C OUT R ESR
Gain
Crossover frequency of 20kHz is a sound first
try if low ESR tantalum capacitors or poscaps
are used at the output. The next step is to calcu-
late the complex conjugate poles contributed by
the LC output filter,
-20db/dec
-40db/dec
f P(LC) =
1
2 π√ LC OUT
Loop
-20db/dec
f
The open loop gain of the whole system can be
divided into the gain of the error amplifier,
PWM modulator, buck converter, and feedback
-20db/dec
resistor divider. In order to crossover at the
selected frequency fco, the gain of the error
amplifier has to compensate for the attenuation
caused by the rest of the loop at this frequency.
In the RC network shown in Figure 4, the product
of R1 and the error amplifier transconductance
Error Amplifier
-20db/dec
f
determines this gain. Therefore, R1 can be deter-
mined from the following equation that takes
into account the typical error amplifier
transconductance, reference voltage and PWM
ramp built into the SP6121.
Figure 5. Frequency response of a stable system and its
error amplifier.
Overcurrent Protection
R1 =
975V OUT f CO f Z(ESR )
V IN f P(LC)2
Over current protection on the SP6121 is imple-
mented through detection of an excess voltage
In Figure 4, R1 and C1 provides a zero f Z1 which
needs to be placed at or below f P(LC) . If f Z1 is
made equal to f P(LC) for convenience, the value
of C1 can be calculated as
condition across the high side PMOS switch
during conduction. This is typically referred to
as high side R DS(ON) detection. By using the
R DS(ON) of Q1 to measure the output current, the
current limit circuit eliminates the sense resistor
C1 =
1
2 π f P(LC) R 1
that would otherwise be required and the corre-
sponding loss associated with it. This improves
the overall efficiency and reduces the number of
C2 =
The optional C2 generates a pole f P1 with R1 to
cut down high frequency noise for reliable op-
eration. This pole should be placed one decade
higher than the crossover frequency to avoid
erosion of phase margin. Therefore, the value of
the C2 can be derived from
1
20 π f CO R 1
Figure 5 illustrates the overall loop frequency
response and frequency of each pole and zero.
components in the power path benefiting size
and cost. R DS(ON) sensing is by default inaccu-
rate and is primarily meant to protect the power
supply during a fault condition. The overcurrent
trip point will vary from unit to unit as the
R DS(ON) of Q1 varies. The SP6121 provides a
built-in 160mV threshold between the I SET and
I SENSE pins. If a current limit threshold in excess
of 160mV is required, an external programming
resistor, R SET can be added between I SET pin and
V IN as shown in Figure 6.
Date: 11/29/04
SP6121 Low Voltage, Synchronous Step Down PWM Controller
12
? Copyright 2004 Sipex Corporation
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SP6121CN-L/TR | 功能描述:电压模式 PWM 控制器 Low Voltage, 8 Pin Synchronous, Cntrllr RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| SP6121EB | 功能描述:电压模式 PWM 控制器 Low Voltage, 8 Pin Sync Buck Controller RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| SP6122 | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters |
| SP6122_04 | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters |
| SP6122ACU | 制造商:Rochester Electronics LLC 功能描述: 制造商:Exar Corporation 功能描述: |
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