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参数资料
| 型号： | L4916 |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 模拟信号调理 |
| 英文描述： | SPECIALTY ANALOG CIRCUIT, PDIP8 |
| 封装： | MINI, POWER, DIP-8 |
| 文件页数： | 4/8页 |
| 文件大小： | 516K |
| 代理商： | L4916 |
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Figure 2 : P.C. Board and Component Layout of Fig. 1 (1 : 1 scale).
PRINCIPLE OF OPERATION
During normal operation (input voltage upper than
VI MIN = VOUT NOM +
VI/O). The device works as a
normal voltage regulator built around the OP1 of the
block diagram.
The series pass element use a PNP-NPN connec-
tion to reduce the dropout. The reference voltage of
the OP1 is derived from a REF through the OP2 and
Q3, acting as an active zener diode of value VREF.
In this condition the device works in the range (1) of
the characteristic of the non linear drop control unit
(see fig.3).
The output voltage is fixed to its nominal value:
R1
VOUT NOM = VREF (1 +
) =
R2
R1
VCFT (1 +
)
R2
R1
= INTERNALLY FIXED RATIO = 2.4
R2
The ripple rejection is quite high (70 dB) and inde-
pendent from CFT value.
On the usual voltage regulators, when the input vol-
tage goes below the nominal value, the regulation
transistors (series element) saturate bringing the
system out of regulation making it very sensible to
every variation of the input voltage. On the contrary,
a control loop on the L4916 consents to avoid the
saturation of the series element by regulating the
value of the reference voltage (pin 2). In fact, when-
ever the input voltage decreases below VI MIN the
supervisor loop, utilizing a non linear OTA, forces
the reference voltage at pin 2 to decrease by dis-
charging CFT. So, during the static mode, when the
input voltage goes below VMIN the drop out is kept
fixed to about 1.6V. In this condition the device
works as a low pass filter in the range (2) of the OTA
characteristic. The ripple rejection is externally ad-
justable acting on CFT as follows :
VI (jw)
SVR (jw) =
=
Vout (jw)
10
-6
1 +
gm
R1
(1 +
)
jwCFT
R2
Where:
gm = 2 . 10
-5 -1 = OTA’S typical transconductance
value on linear region
R1
= fixed ratio
R2
CFT
= value of capacitor in
F
The reaction time of the supervisor loop is given by
the transconductance of the OTA and by CFT. When
the value of the ripple voltage is so high and its ne-
gative peak is fast enough to determine an istanta-
neous decrease of the dropout till 1.2 V, the OTA
works in a higher transconductance condition
[range (3) of the characteristic] and discharge the
capacitor rapidously.
If the ripple frequency is high enough the capacitor
won’t charge itself completely, and the output volt-
age reaches a small value allowing a better ripple re-
jection ; the device’s again working as a filter (fast
transient range).
With CFT = 10
F; f = 100 Hz a SVR of 35 is obtained.
L4916
4/8
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相关代理商/技术参数 |
参数描述 |
|---|---|
| L4918 | 功能描述:线性稳压器 - 标准 8.5V 0.25A w/Filter RoHS:否 制造商:STMicroelectronics 输出类型: 极性: 输出电压:1.8 V 输出电流:150 mA 负载调节: 最大输入电压:5.5 V 线路调整率: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOT-323-5L |
| L492 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:THYRISTOR MODULE|SCR|DUAL|INDEPENDENT|240V V(RRM)|22A I(T) |
| L4920 | 制造商:SGS Thomson 功能描述:LDO Regulator Pos 1.25V to 20V 0.8A 5-Pin(5+Tab) PENTAWATT |
| L4921 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:VERY LOWDROP ADJUSTABLE REGULATORS |
| L4922 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:VERY LOW DROP REGULATOR WITH RESET |
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