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参数资料
| 型号： | SP6123ACN-L |
| 厂商： | Exar Corporation |
| 文件页数： | 14/18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： | 550kHz |
| 占空比： | 93% |
| 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
Most electrolytic and tantalum capacitors come
with adequate ESR value to generate a zero below
power supplies’ crossover frequency. This is cru-
cial to a stable close loop system. However, this
same system can become unstable if ceramic out-
put capacitors are used. The low ESR associated
with ceramic capacitors can push the ESR zero
above the crossover frequency and often higher
than 1MHz. In this case, type III compensation is
In SP6123, G M (error amplifier transconductance)
and R OUT (error amplifier output impedance) are
specified at 0.6ms and 3M ? , respectively.
For frequencies above the second zero f Z2 , the
feedback gain rises at 20dB/dec and is equal to
A FB = 2 π fR Z C 1
However, the error amplifier gain A EA declines
at -20dB/dec due to C P .
required to provide additional low frequency zero for
adequate phase margin and thus stable operation.
A EA =
G M
2 π fC P
f Z1 =
= 6kHz
f Z2 =
= 11.7kHz
2 π (R 2 // R 3 )C Z G M R OUT
The design of type III compensation using
SP6123 transconductance error amplifier is quite
straightforward. First, the resonant frequency of
the LC output filter could be derived from
1
f r = = 11.6kHz
2 π√ L 1 C OUT
The values and references used in all the calcula-
tions agree with the schematic shown in Figure 3.
Select values of R2, C1, R Z and C Z to place two
zeros below or equal to the LC resonant fre-
quency. Those two zeros are located at:
1
2 π R 2 C 1
1
2 π R Z C Z
There is low frequency pole determined by both
the error amplifier gain and feedback gain. It
occurs at
1
f P1 = = 3.25Hz
200
Phase
100
0
Gain
-100
-200
When A FB is less than A EA , the compensated
error amplifier gain is dominated by A FB . As a
result, it shows up as a positive 20dB/dec slope.
However, when the rising A FB crosses the fall-
ing A EA at one particular frequency, the com-
pensated error amplifier gain is now solely de-
termined by A EA . Therefore, the 20dB/dec slope
is converted to a -20dB/dec slope, and the bode
plot demonstrates a double pole at this fre-
quency which is equal to
1 GM
f P2 = 2 π C P C 1 R Z = 221kHz
Select C P such that f P2 is located at least a decade
higher than the crossover frequency.
As shown in Figure 4, this type III compensation
generates a close loop system with 50 degree phase
margin and crossover frequency at 20kHz. This
ensures a stable regulated power supply with tight
DC regulation and fast transient response.
10Hz
100Hz
100Hz
1.0kHz
10kHz
1.0MHz
10MHz
Frequency
Figure 4. Bode Plot for schematic shown in Figure 3. V IN = 3.3V and V OUT = 1.6V, no load.
Date: 9/13/04
SP6123 Low Voltage, Synchronous Step Down PWM Controller
14
? Copyright 2004 Sipex Corporation
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SP6123ACN-L/TR | 功能描述:电压模式 PWM 控制器 Low Voltage, Micro 8 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 |
| SP6123AEN-L | 制造商:Rochester Electronics LLC 功能描述: 制造商:Exar Corporation 功能描述: |
| SP6123CN | 制造商:Exar Corporation 功能描述:Swithed-Mode Power Supply Controller, Voltage Mode Type, 8 Pin, Plastic, SOP |
| SP6123CN/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Low Voltage, Synchronous Step-Down PWM Controller Ideal for 2A to 10A, Small Footprint, DC-DC Power Converters |
| SP6123CN-L | 功能描述:电压模式 PWM 控制器 Low Voltage, Micro 8 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 |
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