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参数资料
| 型号： | IR3821AMTRPBF |
| 厂商： | International Rectifier |
| 文件页数： | 11/21页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 9A 15QFN |
| 产品培训模块： | SupIRBuck™ Integrated Point-of-Load Regulators SupIRBuck? Family and POL Design Tools Overview |
| 标准包装： | 1 |
| 系列： | SupIRBuck™ |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.6 V ~ 12 V |
| 输入电压： | 2.5 V ~ 21 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 300kHz |
| 电流 - 输出： | 9A |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 15-PowerVQFN |
| 包装： | 标准包装 |
| 供应商设备封装： | PQFN（5x6） |
| 产品目录页面： | 1384 (CN2011-ZH PDF) |
| 其它名称： | IR3821AMTRPBFDKR |
PD-60332
IR3821AMPbF
Application Information
Design Example:
The following example is a typical application for
the IR3821A. The application circuit is shown in
page 17.
V in = 12 V,( 13 . 2 V, max )
V o = 1 . 8 V
I o = 9 A
Δ V o ≤ 30 mV
F s = 300 kHz
Output Voltage Programming
Output voltage is programmed by reference
voltage and external voltage divider. The Fb pin
is the inverting input of the error amplifier, which
is internally referenced to 0.6V. The divider is
ratioed to provide 0.6V at the Fb pin when the
output is at its desired value. The output voltage
is defined by using the following equation:
Soft-Start Programming
The soft-start timing can be programmed by
selecting the soft-start capacitance value. The
start-up time of the converter can be calculated
by using:
C SS ? 20 μ A * T start --( 1 )
Where T start is the desired start-up time (ms)
For a start-up time of 11ms, the soft-start
capacitor will be 0.22uF.
Vc supply for single input voltage
To drive the high-side switch, it is necessary to
supply a gate voltage at least 4V greater than the
bus voltage. This is achieved by using a charge
pump configuration as shown in figure 11. This
method is simple and inexpensive. The operation
of the circuit is as follows: when the lower
MOSFET is turned on, the capacitor (C1) is
pulled down to ground and charges, up to V BUS
value, through the diode (D1). The bus voltage
will be added to this voltage when upper
MOSFET turns on in next cycle, and providing
supply voltage (Vc) through diode (D2). Vc is
approximately:
V o = V ref ? ? ? 1 + 8 ? ?
? R ?
? R 9 ?
--( 4 )
V C ? 2 ? V bus ? ( V D 1 + V D 2 )
--( 6 )
Capacitors in the range of 0.1uF are generally
When an external resistor divider is connected to
the output as shown in figure 10.
adequate for most applications. The diodes must
be a fast recovery device to minimize the amount
of charge fed back from the charge pump
capacitor into V BUS . The diodes need to be able
IR3624
IR3821A
Fb
V OU T
R 8
to block the full power rail voltage, which is seen
when the high side MOSFET is switched on. For
low voltage application, schottky diodes can be
used to minimize forward drop across the diodes
at start up.
R 9
Fig. 10: Typical application of the IR3821A for
programming the output voltage
Equation (4) can be rewritten as:
R 9 = R 8 ? ? ?
? ?
? V ref
? V O ? V ref
?
?
--( 5 )
For the calculated values of R 8 and R 9 see
feedback compensation section.
11/04/08
Fig. 11: Charge pump circuit to generate
Vc voltage
11
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