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| 型号： | ADP1871-0.6-EVALZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 26/44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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ADP1870/ADP1871
Data Sheet
EFFICIENCY CONSIDERATIONS
One of the important criteria to consider in constructing a dc-to-dc
converter is efficiency. By definition, efficiency is the ratio of the
output power to the input power. For high power applications at
load currents up to 20 A, the following are important MOSFET
parameters that aid in the selection process:
800
720
640
560
480
V REG = 2.7V
V REG = 3.6V
V REG = 5.5V
?
?
V GS (TH) : the MOSFET threshold voltage applied between
the gate and the source
R DS (ON) : the MOSFET on resistance during channel
400
320
240
?
?
conduction
Q G : the total gate charge
C N1 : the input capacitance of the upper-side switch
160
80
300
400
500
600
700
800
+125°C
+25°C
–40°C
900 1000
?
C N2 : the input capacitance of the lower-side switch
SWITCHING FREQUENCY (kHz)
The following are the losses experienced through the external
component during normal switching operation:
Figure 81. Internal Rectifier Voltage Drop vs. Switching Frequency
Switching Loss
?
?
?
?
?
Channel conduction loss (both of the MOSFETs)
MOSFET driver loss
MOSFET switching loss
Body diode conduction loss (lower-side MOSFET)
Inductor loss (copper and core loss)
The SW node transitions due to the switching activities of the
upper- and lower-side MOSFETs. This causes removal and
replenishing of charge to and from the gate oxide layer of the
MOSFET, as well as to and from the parasitic capacitance
associated with the gate oxide edge overlap and the drain and
source terminals. The current that enters and exits these charge
Channel Conduction Loss
During normal operation, the bulk of the loss in efficiency is due
to the power dissipated through MOSFET channel conduction.
Power loss through the upper-side MOSFET is directly pro-
portional to the duty cycle (D) for each switching period, and
the power loss through the lower-side MOSFET is directly
proportional to 1 ? D for each switching period. The selection
of MOSFETs is governed by the amount of maximum dc load
current that the converter is expected to deliver. In particular,
the selection of the lower-side MOSFET is dictated by the
maximum load current because a typical high current application
paths presents additional loss during these transition times. This
loss can be approximately quantified by using the following
equation, which represents the time in which charge enters and
exits these capacitive regions:
t SW-TRANS = R GATE × C TOTAL
where:
C TOTAL is the C GD + C GS of the external MOSFET.
R GATE is the gate input resistance of the external MOSFET.
The ratio of this time constant to the period of one switching cycle
is the multiplying factor to be used in the following expression:
P N1,N2(CL) ? ? D ? R N1(ON) ? ? 1 ? D ? ? R N2(ON) ? ? I LOAD
P SW ( LOSS ) ?
? I LOAD ? V IN ? 2
employs duty cycles of less than 50%. Therefore, the lower-side
MOSFET is in the on state for most of the switching period.
2
MOSFET Driver Loss
or
t SW - TRANS
t SW
P SW ( LOSS ) ? f SW ? R GATE ? C TOTAL ? I LOAD ? V IN ? 2
Other dissipative elements are the MOSFET drivers. The con-
tributing factors are the dc current flowing through the driver
during operation and the Q GATE parameter of the external MOSFETs.
?
P DR ( LOSS ) ? V DR ? ? f SW C upperFET V DR ? I BIAS ? ? ?
? V REG ? ? f SW C lowerFET V REG ? I BIAS ? ?
where:
C upperFET is the input gate capacitance of the upper-side MOSFET.
C lowerFET is the input gate capacitance of the lower-side MOSFET.
I BIAS is the dc current flowing into the upper- and lower-side drivers.
V DR is the driver bias voltage (that is, the low input voltage
(V REG ) minus the rectifier drop (see Figure 81)).
V REG is the bias voltage.
f SW is the controller switching frequency (300 kHz, 600 kHz, and
1.0 MHz)
Rev. B | Page 26 of 44
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相关代理商/技术参数 |
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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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