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参数资料
| 型号： | LT1683IG |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | Ultralow Noise Push-Pull DC/DC Controller |
| 中文描述： | SWITCHING CONTROLLER, 250 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封装： | 5.30 MM, PLASTIC, SSOP-20 |
| 文件页数： | 10/24页 |
| 文件大小： | 237K |
| 代理商： | LT1683IG |
10
LT1683
1683f
OPERATIOU
In noise sensitive applications switching regulators tend
to be ruled out as a power supply option due to their
propensity for generating unwanted noise. When switch-
ing supplies are required due to efficiency or input/output
constraints, great pains must be taken to work around the
noise generated by a typical supply. These steps may
include pre and post regulator filtering, precise synchro-
nization of the power supply oscillator to an external clock,
synchronizing the rest of the circuit to the power supply
oscillator or halting power supply switching during noise
sensitive operations. The LT1683 greatly simplifies the
task of eliminating supply noise by enabling the design of
an inherently low noise switching regulator power supply.
The LT1683 is a fixed frequency, current mode switching
regulator with unique circuitry to control the voltage and
current slew rates of the output switches. Current mode
control provides excellent AC and DC line regulation and
simplifies loop compensation.
Slew control capability provides much greater control
over the power supply components that can create con-
ducted and radiated electromagnetic interference. Com-
pliance with EMI standards will be an easier task and will
require fewer external filtering components.
The LT1683 uses two external N-channel MOSFETs as the
power switches. This allows the user to tailor the drive
conditions to a wide range of voltages and currents.
CURRENT MODE CONTROL
Referring to the block diagram. A switching cycle begins
with an oscillator discharge pulse, which resets the RS
flip-flop, turning on one of the external MOSFET drivers.
The switch current is sensed across the external sense
resistor and the resulting voltage is amplified and com-
pared to the output of the error amplifier (V
C
pin). The
driver is turned off once the output of the current sense
amplifier exceeds the voltage on the V
C
pin. In this way
pulse by pulse current limit is achieved. The toggle flip-
flop ensures that the two MOSFETs are enabled on alter-
nate clock cycles. Internal slope compensation is provided
to ensure stability under high duty cycle conditions.
Output regulation is obtained using the error amp to set
the switch current trip point. The error amp is a
transconductance amplifier that integrates the difference
between the feedback output voltage and an internal 1.25V
reference. The output of the error amp adjusts the switch
current trip point to provide the required load current at the
desired regulated output voltage. This method of control-
ling current rather than voltage provides faster input
transient response, cycle-by-cycle current limiting for
better output switch protection and greater ease in com-
pensating the feedback loop. The V
C
pin is used for loop
compensation and current limit adjustment. During nor-
mal operation the V
C
voltage will be between 0.25V and
1.27V. An external clamp on V
C
or SS may be used for
lowering the current limit.
The negative voltage feedback amplifier allows for direct
regulation of negative output voltages. The voltage on the
NFB pin gets amplified by a gain of – 0.5 and driven on to
the FB input, i.e., the NFB pin regulates to –2.5V while the
amplifier output internally drives the FB pin to 1.25V as in
normal operation. The negative feedback amplifier input
impedance is 100k (typ) referred to ground.
Soft-Start
Control of the switch current during start up can be
obtained by using the SS pin. An external capacitor from
SS to ground is charged by an internal 9
μ
A current source.
The voltage on V
C
cannot exceed the voltage on SS. Thus
as the SS pin ramps up the V
C
voltage will be allowed to
ramp up. This will then provide for a smooth increase in
switch maximum current. SS will be discharged as a result
of the CS voltage exceeding the short circuit threshold of
approximately 0.22V.
Slew Control
Control of output voltage and current slew rates is achieved
via two feedback loops. One loop controls the MOSFET
drain dV/dt and the other loop controls the MOSFET dI/dt.
The voltage slew rate uses an external capacitor between
CAP A or CAP B and the respective MOSFET drain. These
integrating caps close the voltage feedback loop. The
external resistor R
VSL
sets the current for the integrator.
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相关代理商/技术参数 |
参数描述 |
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| LT1683IG#PBF | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1683IG#TR | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1683IG#TRPBF | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1684 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower Ring Tone Generator |
| LT1684CN | 功能描述:IC RING TONE GENERATOR 14-DIP RoHS:否 类别:集成电路 (IC) >> 接口 - 电信 系列:- 产品培训模块:Lead (SnPb) Finish for COTS 产品变化通告:Product Discontinuation 06/Feb/2012 标准包装:750 系列:* |
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