参数资料
| 型号： | SC412AMLTRT |
| 厂商： | Semtech |
| 文件页数： | 16/22页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 16-MLP |
| 标准包装： | 1 |
| PWM 型： | 控制器 |
| 输出数： | 1 |
| 频率 - 最大： | 325kHz |
| 占空比： | 90% |
| 电源电压： | 3 V ~ 25 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： | -40°C ~ 85°C |
| 封装/外壳： | 16-MLP |
| 包装： | 标准包装 |
| 其它名称： | SC412AMLDKR |
POWER MANAGEMENT
Layout Guidelines
NOT RECOMMENDED FOR NEW DESIGN
SC412A
Layout Guidelines
One or more ground planes are recommended to minimize
the effect of switching noise and copper losses and to
maximize heat removal. The analog ground reference, RTN,
should connect directly to the thermal pad, which in turn
connects to the ground plane through preferably one large
via. There should be a RTN plane or copper are near the
chip; all components that are referenced to RTN should
connect to this plane directly, not through the ground plane,
and located on the chip side of the PCB if possible.
GND should be a separate plane which is not used for
routing analog traces. The VCC input provides power to
the internal analog circuits and the upper and lower gate
drivers.
For an accurate ILIM current sense connection, connect
the ILIM trace to the current sense element (MOSFET or
resistor) directly at the pin of the element, and route that
trace over to the ILIM resistor on another layer if needed.
The layout can be generally considered in two parts; the
control section referenced to RTN, and the switcher power
section referenced to GND.
Looking at the control section ? rst, locate all components
referenced to RTN on the schematic and place these
components near the chip and on the same side if possible.
Connect RTN using a wide trace. Very little current ? ows
in the RTN path and therefore large areas of copper are
not needed. Connect the RTN pin directly to the thermal
pad under the device as the only connection between RTN
and GND.
The VCC supply decoupling capacitor should be tied be-
tween VCC and GND with short traces. All power GND
connections should connect directly to this plane with
special attention given to avoiding indirect connections
between RTN and GND which will create ground loops. As
mentioned above, the RTN plane must be connected to the
GND plane at the chip near the RTN/GND pins.
The chip supply decoupling capacitor (VCC/GND) should
be located near to the pins. Since the DL pin is directly
between VCC and GND, and the DL trace must be a wide,
direct trace, the VCC decoupling capacitor is best placed
on the opposite side of the PCB, routed with traces as short
as possible and using at least two vias when connecting
through the PCB.
The switcher power section should connect directly to the
ground plane(s) using multiple vias as required for current
handling (including the chip power ground connections).
Power components should be placed to minimize loops
and reduce losses. Make all the power connections on
one side of the PCB using wide copper ? lled areas if
possible. Do not use “minimum” land patterns for power
components. Minimize trace lengths and maximize trace
widths between the gate drivers and the gates of the
MOSFETs to reduce parasitic impedances (and MOSFET
switching losses); the low-side MOSFET is most critical.
Maintain a length to width ratio of <20:1 for gate drive
signals. Use multiple vias as required by current handling
requirement (and to reduce parasitic) if routed on more
than one layer.
There are two sensitive, feedback-related pins at the chip:
VOUT and FB. Proper routing is needed to keep noise
away from these signals. All components connected to
FB should be located directly at the chip, and the copper
area of the FB node minimized. The VOUT trace that
feeds into the VOUT pin, which also feeds the FB resistor
divider, must be kept far away from noise sources such
as switching nodes, inductors and gate drives. Route the
VOUT trace in a quiet layer if possible, from the output
capacitor back to the chip.
For the switcher power section, there are a few key
guidelines to follow:
? 2006 Semtech Corp.
16
www.semtech.com
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