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| 型号： | MC34704BEPR2 |
| 厂商： | Freescale Semiconductor |
| 文件页数： | 44/54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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C1 = ------------------ ? ---------------- 2 ? ? ? ? ?
Vin min ? 1 ? 1
2 π ( F PO R1 )
C2 = ? ? ? ?
----------------------------
R2 = ? ---------------------------- ?
R3 = ? ---------------------------- ?
C3 = ? ---------------------------- ?
FUNCTIONAL DEVICE OPERATION
COMPONENT CALCULATION
The passive components associated to these frequencies are calculated with the following formulas
-----------------------------
V RAMP ? D ′ min ?
1
2 π ( F Z2 R1 )
1
? 2 π ( F Z1 C1 ) ?
1
? 2 π ( F P1 C2 ) ?
1
? 2 π ( F P2 R2 ) ?
On the 34704 V RAMP is half of 1.2 V since each operation mode spends only half the ramp.
Io max dtI
Δ Vo max
L min ≥ -----------------------------------------------------------------------------------------------------------
L min ≥ D ′ T ------------
Vo ( 1 – D min )
Regulator 3 (Synchronous Buck - internally
compensated)
? 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
2I OB
Vo [H]
2I OB
? 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.
? First calculate the dt_I (inductor current rising time)
given by:
? Then the output capacitor can be chosen as follow:
[F]
C OUT ≤ ----------------------
Where Δ VO max is the maximum allowed transient
overshoot expressed as a percentage of the output voltage,
typically from 3 to 5% of Vo.
? Finally find the maximum allowed ESR to allow the
desired transient response:
Δ Vo r ( Fsw ) ( L ) [ Ω ]
ESR max = -------------------------------------
NOTE: do not use the parameters Δ VO R and Δ VO max
indistinctly, the first one indicates the output voltage rip-
ple, while the second one is the maximum output volt-
age overshoot (transient response).
? R1 and RB: These two resistors help to set the output
voltage to the desire value using a V REF =0.6 V, select R1
between 10 k and 100 K and then calculate RB as follows:
Io max T [s]
Δ Iostep
RB = ---------------------
dtI = --------------------
Where the parameter Δ IO _ step is the maximum current
step during the current rising time and is define as:
R1
Vo
----------- – 1
Vref
Regulator 8 (Synchronous Boost - internally
compensated -Voltage or current feedback)
[ Ω ]
Δ Iostep = ? ? ? ? ? ? ? ?
D max Vin min – Vo
------------- -------------------------------
Fsw L
[A]
REG8 is a Synchronous Boost converter set to 15V with a
maximum current of 30 mA and can be used with voltage
34704
Analog Integrated Circuit Device Data
44
Freescale Semiconductor
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