参数资料
型号: SI786CG-T1-E3
厂商: Vishay Siliconix
文件页数: 12/16页
文件大小: 236K
描述: IC REG QD BUCK/LINEAR 28SSOP
标准包装: 1,800
拓扑: 降压(降压)(2),线性(LDO)(2)
功能: 任何功能
输出数: 4
频率 - 开关: 300kHz,200kHz
电压/电流 - 输出 1: 控制器
电压/电流 - 输出 2: 控制器
电压/电流 - 输出 3: 5V,5mA
带 LED 驱动器:
带监控器:
带序列发生器:
电源电压: 5.5 V ~ 30 V
工作温度: 0°C ~ 70°C
安装类型: 表面贴装
封装/外壳: 28-SSOP(0.209",5.30mm 宽)
供应商设备封装: 28-SSOP
包装: 带卷 (TR)
www.vishay.com
12
Document Number: 70189
S-40807-Rev. J, 26-Apr-04
Vishay Siliconix
Si786
Product is End of Life 3/2014
OPERATIONAL MODES
PWM Mode
The 3.3 V and 5 V Buck controllers operate in continuous-
current PWM mode when the load demands more than
approximately 25 % of the maximum current (see typical
curves). The duty cycle can be approximated as Duty_Cycle
= V
OUT
/V
IN
 .
In this mode, the inductor current is continuous; in the first
half of the cycle, the current slopes up when the high-side
MOSFET conducts and then, in the second half, slopes back
down when the inductor is providing energy to the output
capacitor and load. As current enters the inductor in the first
half-cycle, it is also continuing through to the load; hence, the
load is receiving continuous current from the inductor. By
using this method, output ripple is minimized and smaller
form-factor inductors can be used. The output capacitors
ESR has the largest effect on output ripple. It is typically
under 50 mV; the worst case condition is under light load with
higher input battery voltage.
Pulse-Skipping Mode
When the load requires less than 25 % of its maximum, the
Si786 enters a mode which drives the gate for one clock
cycle and skips the majority of the remaining cycles. Pulse-
skipping mode cuts down on the switching losses, the domi-
nant power consumer at low current levels.
In the region between pulse-skipping mode and PWM mode,
the controller may transition between the two modes, deliv-
ering spurts of pulses. This may cause the current waveform
to look irregular, but will not overly affect the ripple voltage.
Even in this transitional mode efficiency will stay high.
Current Limit
The current through an external resistor, is constantly moni-
tored to protect against over-current. A low value resistor is
placed in series with the inductor. The voltage across it is
measured by connecting it between CS_ and FB_. If this volt-
age is larger than 100 mV, the high-side MOSFET drive is
shut down. Eliminating over-currents protects the MOSFET,
the load and the power source. Typical values for the sense
resistors with a 3 A load will be 25 m?
Figure 4. Boost Supply for Gate Drivers
Level
Translator
DH_
BST_
LX_
DL_
V
L
PWM
V
L
V
L
BATTERY
INPUT
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SI786CRG-T1-E3 功能描述:开关变换器、稳压器与控制器 Dual 3.45V Step-Down RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel
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