参数资料
型号: NCP5386AMNR2G
厂商: ON Semiconductor
文件页数: 31/33页
文件大小: 0K
描述: IC CTLR BUCK 1/2PHASE 32-QFN
标准包装: 2,500
应用: 控制器,Intel VR10、VR11、AMD CPU
输入电压: 4.75 V ~ 5.25 V
输出数: 2
工作温度: 0°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 32-VFQFN 裸露焊盘
供应商设备封装: 32-QFN(5x5)
包装: 带卷 (TR)
NCP5386, NCP5386A, NCP5386B
V OUT RFB · DCR · 6
I OUT
+ Z OUT +
RDRP
RFB · DCR · 6
RDRP +
RFB is always set to 1.0 k W and RFB1 is usually set to
100 W for maximum phase boost. The value of RF is
typically set to 4.0 k W .
Droop Injection and Thermal Compensation
The VDRP signal is generated by summing the sensed
output currents for each phase and applying a gain of
approximately six. VDRP is externally summed into the
feedback network by the resistor RDRP. This induces an
offset which is proportional to the output current thereby
forcing the controlled resistive output impedance.
RRDP determines the target output impedance by the
basic equation:
(eq.
10)
Z OUT
The value of the inductor ’s DCR varies with temperature
according to the following equation 10:
DCR Tmax + DCR 25C · (1 ) 0.00393 · C ? 1(T max * 25 · C))
(eq. 11)
The system can be thermally compensated to cancel this
effect out to a great degree by adding an NTC (negative
temperature coefficient resistor) in parallel with RFB to
reduce the droop gain as the temperature increases. The
NTC device is nonlinear. Putting a resistor in series with the
NTC helps make the device appear more linear with
temperature. The series resistor is split and inserted on both
sides of the NTC to reduce noise injection into the feedback
loop. The recommended value for RISO1 and RISO2 is
approximately 1.0 k W .
The output impedance varies with inductor temperature by the equation:
Z OUT(T) +
RFB · DCR25C · (1 ) 0.00393 · C ? 1(T max ? 25C)) · 6
R droop
(eq. 12)
By including the NTC RT2 and the series isolation resistors the new equation becomes:
Z OUT(T) +
RFB · (RISO1 ) RT2(T) ) RISO2)
RFB ) RISO1 ) RT2(T) ) RISO2
· DCR25C · (1 ) 0.00393 · C ? 1(T max ? 25C)) · 6
R droop
(eq. 13)
1 1
RT2(T) + RT225C · e b
*
298
273 ) T
The typical equation of a NTC is based on a curve fit
equation 13.
(eq. 14)
The demo board is populated with a 10 k W NTC with a
Beta of 4300. Figure 34 shows the uncompensated and
compensated output impedance versus temperature.
ON Semiconductor provides an excel spreadsheet to
help with the selection of the NTC. The actual selection of
the NTC will be effected by the location of the output
inductor with respect to the NTC and airflow, and should
be verified with an actual system thermal solution.
VRFAN
Thermal monitoring provides one threshold sensitive
comparator for thermal monitoring. The circuit consists of
one comparator that compares the voltage on the NTC pin
to an internal resistor divider connected to V CC .
The following equations can be used to find the
temperature trip points.
RT1(T) + RT125C · e b
1
273 ) T
*
1
298
(eq. 15)
RatioNTC(T) :
RNTC2 ) RT1(T)
RNTC1 ) RNTC2 ) RT1(T)
(eq. 16)
The demo board contains a 68 K NTC for RT1 with a
Figure 34. Uncompensated and Compensated Output
Impedance vs. Temperature
Beta of 4750. RNTC1 is populated with 15 k W and RNTC2
is populated with a zero ohm resistor. Figure 35 is a plot of
Equation 16. The horizontal trip thresholds intersect the
http://onsemi.com
31
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