参数资料
| 型号： | EL7520AILZ-T7 |
| 厂商： | Intersil |
| 文件页数： | 12/18页 |
| 文件大小： | 0K |
| 描述： | IC CTRLR DC/DC 4-CHAN 20-QFN |
| 标准包装： | 1,000 |
| 应用： | 控制器，TFT LCD |
| 输入电压： | 3 V ~ 5.5 V |
| 输出数： | 4 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-VFQFN 裸露焊盘 |
| 供应商设备封装： | 20-QFN 裸露焊盘（4x4） |
| 包装： | 带卷 (TR) |
EL7520, EL7520A
I LAVG = -------------
Input Capacitor
The input capacitor is used to supply the current to the
converter. It is recommended that C IN be larger than 10μF.
The reflected ripple voltage will be smaller with larger C IN .
The voltage rating of input capacitor should be larger than
maximum input voltage.
Boost Inductor
A 3.3μH inductor is recommended due to the fixed internal
slope compensation. The inductor must be able to handle
the following average and peak current:
I O
1 – D
2
? I L
I LPK = I LAVG + --------
Switching MOSFET
Due to the parasitic inductance of the trace, the MOSFET
will experience spikes higher that the output voltage when
the MOSFET turns off. Thus, a MOSFET with enough
voltage margin is needed.
The R DS(ON) of the MOSFET is critical for power dissipation
and current limit. A MOSFET with low R DS(ON) is desired to
get high efficiency and output current, but very low R DS(ON)
will reduce the loop stability. A MOSFET with 20m ? to 50m ?
R DS(ON) is recommended. Some recommended MOSFETs
are shown in following table.
For low ESR ceramic capacitors, the output ripple is
dominated by the charging and discharging of the output
capacitor. The voltage rating of the output capacitor should
be greater than the maximum output voltage.
Compensation
The EL7520 and EL7520A can operate in either P mode or
PI mode. Connecting C INT pin directly to V IN will enable
P mode. For better load regulation, use PI mode with a
2.2nF capacitor between C INT and ground.
Linear-Regulator Controllers (V ON , V LOGIC , and
V OFF )
The EL7520, EL7520A include three independent linear-
regulator controllers, in which two are positive output voltage
(V ON and V LOGIC ), and one is negative. The V ON , V OFF ,
and V LOGIC linear-regulator controller functional diagrams,
applications circuits are shown in Figures 27, 28, and 29
respectively.
Calculation of the Linear Regulator Base-Emitter
Resistors (R BL , R BP and R BN )
For the pass transistor of the linear regulator, low frequency
gain (Hfe) and unity gain freq. (f T ) are usually specified in the
datasheet. The pass transistor adds a pole to the loop transfer
function at f p = f T /Hfe. Therefore, in order to maintain phase
margin at low frequency, the best choice for a pass device is
often a high frequency low gain switching transistor. Further
improvement can be obtained by adding a base-emitter resistor
PART
NUMBER
FDC655AN
TABLE 2. RECOMMENDED MOSFETs
MANUFACTURER FEATURE
Fairchild 6.3A, 30V, R DS(ON) = 23m ?
Semiconductor
R BE (R BP , R BL , R BN in the Functional Block Diagram), which
increase the pole frequency to: f p = f T *(1+ Hfe *re/R BE )/Hfe,
where re = KT/qIc. So choose the lowest value R BE in the
design as long as there is still enough base current (I B ) to
support the maximum output current (I C ).
FDS4488
Si7844DP
SI6928DQ
Fairchild
Semiconductor
Vishay
Vishay
7.9A, 30V, R DS(ON) = 22m ?
10A, 30V, R DS(ON) = 22m ?
20A, 30V, R DS(ON) = 30m ?
We will take as an example the V LOGIC linear regulator. If a
Fairchild FMMT549 PNP transistor is used as the external
pass transistor, Q31 in the application diagram, then for a
maximum V LOGIC operating requirement of 500mA the data
sheet indicates Hfe_min = 100.
V RIPPLE = I LPK × ESR + ------------------------ × ---------------- × -----
V C f
Rectifier Diode
A high-speed diode is desired due to the high switching
frequency. Schottky diodes are recommended because of
their fast recovery time and low forward voltage. The rectifier
diode must meet the output current and peak inductor
current requirements.
Output Capacitor
The output capacitor supplies the load directly and reduces the
ripple voltage at the output. Output ripple voltage consists of
two components: the voltage drop due to the inductor ripple
current flowing through the ESR of output capacitor, and the
charging and discharging of the output capacitor.
V O – V IN I O 1
O OUT S
12
The base-emitter saturation voltage is: Vbe_max = 1.25V (note
this is normally a Vbe ~ 0.7V, however, for the Q5 transistor an
internal Darlington arrangement is used to increase it's current
gain, giving a 'base-emitter' voltage of 2 x V BE ).
(Note that using a high current Darlington PNP transistor for
Q5 requires that V IN > V LOGIC + 2V. Should a lower input
voltage be required, then an ordinary high gain PNP
transistor should be selected for Q5 so as to allow a lower
collector-emitter saturation voltage).
For the EL7520, EL7520A, the minimum drive current is:
I_DRVL_min = 8mA
FN7318.0
July 12, 2005
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相关代理商/技术参数 |
参数描述 |
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| EL7520ILZ | 功能描述:电流型 PWM 控制器 EL7520ILZ 4-CH DC-DC CNTRLR RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| EL7520ILZ-T13 | 功能描述:电流型 PWM 控制器 EL7520ILZ 4-CH DC-DC CNTRLR RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| EL7520ILZ-T7 | 功能描述:电流型 PWM 控制器 EL7520ILZ 4-CH DC-DC CNTRLR RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| EL7530 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:Monolithic 600mA Step-Down Regulator with Low Quiescent Current |
| EL7530_06 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:Monolithic 600mA Step-Down Regulator with Low Quiescent Current |
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