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| 型号： | ADP1874-0.6-EVALZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 28/44页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR ADP1874 |
| 标准包装： | 1 |
| 系列： | * |
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Z COMP =
× f CROSS 2 + f ZERO 2
ADP1874/ADP1875
Ceramic capacitors are known to have low ESR. However, there
is a trade-off in using the popular X5R capacitor technology
because up to 80% of its capacitance may be lost due to derating
as the voltage applied across the capacitor is increased (see
available selection is limited to 22 μF maximum.
20
Data Sheet
Error Amplifier Output Impedance (Z COMP )
Assuming that C C2 is significantly smaller than C COMP , C C2 can
be omitted from the output impedance equation of the error
amplifier. The transfer function simplifies to
R COMP
f CROSS
10
X7R (50V)
and
0
–10
–20
f CROSS =
1
12
× f SW
–30
–40
where f ZERO , the zero frequency, is set to be 1/4 the crossover
–50
–60
–70
–80
–90
–100
X5R (25V)
X5R (16V)
10μF TDK 25V, X7R, 1210 C3225X7R1E106M
22μF MURATA 25V, X7R, 1210 GRM32ER71E226KE15L
47μF MURATA 16V, X5R, 1210 GRM32ER61C476KE15L
Error Amplifier Gain (G m )
The error amplifier gain (transconductance) is
G m = 500 μA/V (μs)
Current-Sense Loop Gain (G CS )
0
5
10 15 20
DC VOLTAGE (V DC )
25
30
The current-sense loop-gain is
G CS =
1
A CS × R ON
H = 1 V/V = G M × G CS ×
× Z COMP × Z FILT
f CROSS =
f SW
Figure 86. Capacitance vs. DC Voltage Characteristics for Ceramic Capacitors
Electrolytic capacitors satisfy the bulk capacitance requirements
for most high current applications. However, because the ESR
of electrolytic capacitors is much higher than that of ceramic
capacitors, several MLCCs should be mounted in parallel with
the electrolytic capacitors to reduce the overall series resistance.
COMPENSATION NETWORK
require Type II compensation. To determine the component
values needed for compensation (resistance and capacitance
values), it is necessary to examine the converter’s overall loop
gain (H) at the unity gain frequency (f SW /10) when H = 1 V/V.
V REF
V OUT
Examining each variable at high frequency enables the unity-
gain transfer function to be simplified to provide expressions
for the R COMP and C COMP component values.
(A/V)
where:
A CS (V/V) is programmable for 3 V/V, 6 V/V, 12 V/V, and 24 V/V
(see the Programming Resistor (RES) Detect Circuit and Valley
Current-Limit Setting sections).
R ON is the channel impedance of the lower side MOSFET.
Crossover Frequency
The crossover frequency is the frequency at which the overall
loop (system) gain is 0 dB (H = 1 V/V). It is recommended for
current-mode converters, such as the ADP1874, that the user
set the crossover frequency between 1/10 and 1/15 the
switching frequency.
1
12
The relationship between C COMP and f ZERO (zero frequency) is as
follows:
Output Filter Impedance (Z FILT )
Examining the filter’s transfer function at high frequencies
f ZERO =
1
2 π × R COMP × C COMP
simplifies to
The zero frequency is set to 1/4 the crossover frequency.
Z FILTER = R L ×
1 + s × ESR × C OUT
1 + s ( R L + ESR ) C OUT
Combining all of the above parameters results in
R COMP =
f CROSS + f ZERO
V
at the crossover frequency (s = 2πf CROSS ). ESR is the equivalent
series resistance of the output capacitors.
f CROSS
2
2
×
1 2 + ( s ( R L + ESR ) C OUT ) 2
1 2 + ( s × ESR × C OUT ) 2
×
1
R L
× OUT ×
V REF
1
G M G CS
where ESR is the equivalent series resistance of the output
capacitors.
Rev. A | Page 28 of 44
C COMP =
1
2 × π × R COMP × f ZERO
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ADP1874-1.0-EVALZ | 功能描述:BOARD EVAL FOR ADP1874 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:* 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| ADP1874ARQZ-0.3-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 16-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 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:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| ADP1874ARQZ-0.6-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 16-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| ADP1874ARQZ-1.0-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 16-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| ADP1875 | 制造商:AD 制造商全称:Analog Devices 功能描述:Synchronous Buck Controller with Constant On-Time and Valley Current Mode |
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