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| 型号： | MC34704BEPR2 |
| 厂商： | Freescale Semiconductor |
| 文件页数： | 40/54页 |
| 文件大小： | 0K |
| 描述： | IC PWR MNGMT DC-DC MULT 56-QFN |
| 特色产品： | MC34704 Multi-channel Power Management IC (PMIC) |
| 标准包装： | 1 |
| 应用： | 处理器 |
| 电流 - 电源： | 86mA |
| 电源电压： | 2.7 V ~ 5.5 V |
| 工作温度： | -20°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 56-VFQFN 裸露焊盘 |
| 供应商设备封装： | 56-QFN-EP（7x7） |
| 包装： | 标准包装 |
| 产品目录页面： | 809 (CN2011-ZH PDF) |
| 其它名称： | MC34704BEPR2DKR |
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FUNCTIONAL DEVICE OPERATION
COMPONENT CALCULATION
1. Define I OB as the minimum current to maintain CCM as
15% of full load.
regulators may work as a buck or a boost depending on the
operating voltages, they need to be compensated in different
ways for each situation.
Since the 34704 is meant to work using a LiIon battery, the
Vo ( D ) ( 1 – D ) T
L min ≥ ------------------------------------------
2I OB
2
(H)
operating input voltage range is set from 2.7 - 4.2 V, then the
following scenarios are possible:
where: D = Dutycycle
Vo = Output Voltage
T = Switching Period
IOB = Boundary Current to achieve CCM
2. However the worst case condition for the boost power
stage is when the input voltage is equal to one half of
the output voltage, which results in the Maximum Δ I L ,
then:
Regulator
2
Vo
2.8 V
3.3 V
3.3 V
Input voltage
range
3.0 - 4.2
2.7 - 3.0
3.5 - 4.2
Operation
Buck
Boost
Buck
L min ≥ ----------------
Vo ( T )
16I OB
(H)
4
1.8 V
2.5 V
2.7 - 4.2
2.7 - 4.2
Buck
Buck
Note: On the 34704B Use the recommended 3.0uH
inductor rated between 50 to 100 mA in order to have this
regulator working in DCM. Rising the inductor value will make
the regulator to begin working in CCM.
5
3.3 V
3.3 V
2.7 - 3.0
3.5 - 4.2
Boost
Buck
? C OUT : The three elements of output capacitor that
contribute to its impedance and output voltage ripple are
the ESR, the ESL and the capacitance C. The minimum
capacitor value is approximately:
? NOTE: Since these 3 regulators can work as a buck or a
boost in a single application, a good practice to configure
these regulators is to compensate for a boost scenario and
then verify that the regulator is working in buck mode using
that same compensation.
C OUT ≥ ----------------------------
Io max D max
Fsw Δ Vo r
(F)
Compensating for Buck operation:
Δ Vo r
? ---------------------- + I
? 1 – D max
L min ≥ ----------------------------------------------------------------------------------------------------------------------- ≈ D ′ MAX T --------------
where: Dmax = Maximum Dutycycle
FSW = Switching Frequency
? Where Δ VO r is the desired output voltage ripple.
? Now calculate the maximum allowed ESR to reach the
desired Δ VO r .
ESR ≤ ------------------------------------------- [ Ω ]
Io max ?
OB ?
? 1CVG (Only Reg1) : Use a 47uF capacitor from Ground to
VG.
? D1 (Only Reg1) : Use a fast recovery schottky diode rated
to 10V at 1A.
Regulator 2, 4 and 5 (Synchronous Buck-Boost regulator
with external compensation)
These three regulators are 4-Switch synchronous buck-
boost voltage mode control DC-DC regulator that can
? L: A buck power stage can be designed to operate in CCM
for load currents above a certain level usually 5 to 15% of
full load. The minimum value of inductor to maintain CCM
can be determined by using the following procedure:
1. Define I OB as the minimum current to maintain CCM
between 10 to 15% of full load.
( Vo + Io max ( R DSONLSFET + R L ) D ′ min ) T Vo
2I OB 2IOB
[H]
where: RDSONLSFET = Body Resistance of the Lowside Fet
RL = Inductor Winding Resistance
D'Min = Minimum Off Percentage given by 1- (Vin_min/Vout_max)
D'max = Maximum Off Percentage given by 1- (Vin_max/Vout_min)
? C OUT : The three elements of output capacitor that
contribute to its impedance and output voltage ripple are
the ESR, the ESL and the capacitance C. A good
approach to calculate the minimum real capacitance
needed is to include the transient response analysis to
control the maximum overshoot as desired.
operate at various output voltage levels. Since each of the
34704
Analog Integrated Circuit Device Data
40
Freescale Semiconductor
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