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参数资料
| 型号： | ADP1871-0.6-EVALZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 25/44页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR ADP1871-0.6 |
| 标准包装： | 1 |
| 系列： | * |
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R COMP ( f CROSS + f ZERO )
Z COMP =
DataSheet
Ceramic capacitors are known to have low ESR. However, the
trade-off of using X5R technology is that up to 80% of its capaci-
tance might be lost due to derating as the voltage applied across
the capacitor is increased (see Figure 80). Although X7R series
capacitors can also be used, the available selection is limited to
only up to 22 μF.
20
ADP1870/ADP1871
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
f CROSS
f CROSS =
× f SW
10
0
–10
–20
–30
–40
–50
X7R (50V)
X5R (25V)
and
1
12
where f ZERO , the zero frequency, is set to be 1/4 th of the crossover
frequency for the ADP1870.
Error Amplifier Gain (G M )
–60
–70
–80
–90
–100
0
X5R (16V)
10μF TDK 25V, X7R, 1210 C3225X7R1E106M
22μF MURATA 25V, X7R, 1210 GRM32ER71E226KE15L
47μF MURATA 16V, X5R, 1210 GRM32ER61C476KE15L
5 10 15 20 25
30
The error amplifier gain (transconductance) is
G M = 500 μA/V
Current-Sense Loop Gain (G CS )
The current-sense loop gain is
H = 1 V/V = G M × G CS ×
× Z COMP × Z FILT
G CS =
1
A CS × R ON
f CROSS =
f SW
DC VOLTAGE (V DC )
Figure 80. Capacitance vs. DC Voltage Characteristics for Ceramic Capacitors
Electrolytic capacitors satisfy the bulk capacitance requirements
for most high current applications. Because the ESR of electrolytic
capacitors is much higher than that of ceramic capacitors, when
using electrolytic capacitors, several MLCCs should be mounted
in parallel to reduce the overall series resistance.
COMPENSATION NETWORK
Due to their current-mode architecture, the ADP1870/ADP1871
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 OUT
V REF
Examining each variable at high frequency enables the unity-
gain transfer function to be simplified to provide expressions
(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). For current-mode
converters, such as the ADP1870, it is recommended that the
user set the crossover frequency between 1/10 th and 1/15 th of the
switching frequency.
1
12
The relationship between C COMP and f ZERO (zero frequency) is as
follows:
for the R COMP and C COMP component values.
Output Filter Impedance (Z FILT )
f ZERO =
1
2 π × R COMP × C COMP
)
Z FILTER =
f CROSS 2 π f CROSS C OUT V
f CROSS + f ZERO
R COMP = × × OUT
C COMP =
Examining the filter’s transfer function at high frequencies
simplifies to
1
sC OUT
at the crossover frequency (s = 2πf CROSS ).
The zero frequency is set to 1/4 th of the crossover frequency.
Combining all of the above parameters results in
G M G CS V REF
1
2 × π × R COMP × f ZERO
Rev. B | Page 25 of 44
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| ADP1871-1.0-EVALZ | 功能描述:BOARD EVAL FOR ADP1871-1.0 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 |
| ADP1871ACPZ-0.3-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 10LFCSP 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) |
| ADP1871ACPZ-0.6-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 10LFCSP 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) |
| ADP1871ACPZ-1.0-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 10LFCSP 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) |
| ADP1871ARMZ-0.3-R7 | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP 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) |
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