参数资料
型号: IR3856MTR1PBF
厂商: International Rectifier
文件页数: 13/35页
文件大小: 0K
描述: IC REG BUCK SYNC ADJ 6A PQFN15
产品培训模块: 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: 0.7 V ~ 18.9 V
输入电压: 1.5 V ~ 21 V
PWM 型: 电压模式
频率 - 开关: 225kHz ~ 1.65MHz
电流 - 输出: 6A
同步整流器:
工作温度: -40°C ~ 125°C
安装类型: 表面贴装
封装/外壳: 17-PowerVQFN
包装: 标准包装
供应商设备封装: 17-PQFN(5x6)
其它名称: IR3856MTR1PBFDKR
PD-97528
IR3856MPbF
Figure 3c. shows the recommended startup
sequence for sequenced operation of IR3856
with Enable used as logic input.
Fig. 5. Pre-Bias startup pulses
Soft-Start
The IR3856 has a programmable soft-start to
control the output voltage rise and to limit the
current surge at the start-up. To ensure correct
start-up, the soft-start sequence initiates when
the Enable and Vcc rise above their UVLO
thresholds and generate the Power On Ready
( 1.4 - 0.7 ) * C SS
T start = - - - - - - - - - - - - - - - - - - - - (1)
Fig. 3c. Recommended startup sequence,
Sequenced operation
Pre-Bias Startup
IR3856 is able to start up into pre-charged
output, which prevents oscillation and
disturbances of the output voltage.
The output starts in asynchronous fashion and
keeps the synchronous MOSFET off until the first
gate signal for control MOSFET is generated.
(POR) signal. The internal current source
(typically 20uA) charges the external capacitor
C ss linearly from 0V to 3V. Figure 6 shows the
waveforms during the soft start.
The start up time can be estimated by:
20 μ A
During the soft start the OCP is enabled to
protect the device for any short circuit and over
current condition.
Figure 4 shows a typical Pre-Bias condition at
start up.
The synchronous MOSFET always starts with a
narrow pulse width and gradually increases its
duty cycle with a step of 25%, 50%, 75% and
100% until it reaches the steady state value. The
number of these startup pulses for the
synchronous MOSFET is internally programmed.
Figure 5 shows a series of 32, 16, 8 startup
pulses.
Fig. 6. Theoretical operation waveforms
during soft-start
Fig. 4. Pre-Bias startup
Rev 4.0
13
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