参数资料
| 型号： | A8670EESTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 20/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 2A 20QFN |
| 标准包装： | 1 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 可调至 0.6V |
| 输入电压： | 7 V ~ 16 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 200kHz ~ 1MHz |
| 电流 - 输出： | 2A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-WFQFN 裸露焊盘 |
| 包装： | 标准包装 |
| 供应商设备封装： | 20-QFN 裸露焊盘（4x4） |
| 其它名称： | 620-1397-6 |
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A8670
Fixed Frequency, 2 A Synchronous Buck Regulator
With Fault Warnings and Power OK
Layout
Although the power dissipation in the A8670 is very low, it is
recommended that the thermal pad of the device is soldered to
an appropriate pad on the printed circuit board to help minimize
the junction temperature and enhance the efficiency. The PCB
pad should in turn be connected to the ground plane via a number
of thermal vias. As a suggestion, the following could be used:
sixteen vias, arranged in 4 rows of 4, with diameter 0.25 mm
and spaced (pitch) 0.6 mm apart. The PCB pad as well as acting
as a thermal connection, also forms the star connection for the
grounding system.
Figure 7 illustrates the key objectives in the grounding system.
The filtering capacitors: C1, C3, C4, and C6 should be connected
as close as possible to their respective pins. The ground connec-
tions for each of the capacitors should be returned directly to the
star connection (PCB pad). Again, these connections should be as
short as possible. Both the PGND and AGND connections should
connect directly to the PCB pad to form the star connection.
A8670 Support
Components
The ground return connection for the feedback resistor should be
Kelvin-connected directly back to the star ground. Note: To avoid
voltage offset errors in the output voltage, the feedback resistor
should not be connected to the filter capacitor or load grounds
returns.
The support components (C5, C7, and C8) that are ground refer-
enced should be connected together locally and then a common
trace used to return directly to the star connection. Again, this
ground should not pick-up any of the filter capacitors or load
ground returns.
Due to the high impedance nature of the COMP node, it is
important to ensure the compensation components are connected
as close as possible. The feedback trace from R5 and R6 to the
FB pin is also a high impedance input and should be as short as
possible and be placed well away from noisy connections such
as LX. It is recommended to keep any ground planes well away
from the LX node to avoid any potential noise coupling effects.
C5
SS
C7
R4
C8
COMP
A8670
L1
Local ‘quiet’
Ground Trace
Ground Plane
C1
C6
VIN
BIAS
LX
C3/C4
R5
PGND
Thermal Pad
AGND
R6
Figure 7. Layout considerations for mounting the A8760
Thermal Vias
Ground Plane (internal or bottom side of PCB)
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
19
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