参数资料
型号: MC34702EK
厂商: Freescale Semiconductor
文件页数: 30/39页
文件大小: 0K
描述: IC POWER SUPPLY MCU 3A 32-SOIC
标准包装: 42
应用: 电源
电流 - 电源: 60mA
电源电压: 2.8 V ~ 6 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 32-SOIC(0.295",7.50mm 宽)
供应商设备封装: 32-SOIC
包装: 管件
配用: KIT33702DWBEVB-ND - KIT FEATURES THE MC34701
TYPICAL APPLICATIONS
TYPICAL APPLICATIONS
BUCK REGULATOR CONTROL CIRCUIT
The 34702 buck regulator utilizes a PWM Voltage Mode
load regulation. The control circuit block diagram is shown in
topology with feed-forward to achieve an excellent line and
L
Figure 29. Buck Regulator Control Circuit
f z ? c ? = -------------------------------------------
The integrated 40pF capacitor C F charged through the
external resistor R4 provides the feed-forward ramp
waveform, the amplitude of which is proportional to the input
voltage, thus providing the feed-forward function.
Figure 30 shows the Bode plot of the 34702 buck regulator
control loop gain and phase versus frequency.
The first double pole on the Bode plot is created by the
buck regulator output L-C filter, and its frequency can be
1
2 ? C2 ? R1 + R3 ?
The feed-forward implemented by resistor R4 and
integrated capacitor C F creates a pole in the overall loop
transfer function, the frequency of which can be calculated
from the following formula.
f LC = -----------------------
f p ? FF ? = ---------------------------------------------------------------- ? -----------------------
------- ? -------------------------------- + V m1
calculated as:
1
2 ? C O L
f sw R4C F
V IN 1
1 ? V IN – V Ref ? 2 ? R4C F
Where C O is the value of the buck output capacitor and L
is the inductance value of the output filter inductor L.
The frequency of the compensating zero can be calculated
as follows.
Where V Ref is the buck regulator reference voltage ?
(V Ref = 0.8V typ.) at the INV pin, ?
V IN is the buck regulator input voltage, ?
V m1 is the ramp generated by the internal ramp
generator (V m1 = 0.5V typ.).
34702
Analog Integrated Circuit Device Data ?
30
Freescale Semiconductor
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