参数资料
| 型号： | FAN8303MX |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 8/12页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 2A 8SOIC |
| 标准包装： | 1 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.6 V ~ 20 V |
| 输入电压： | 5 V ~ 23 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 370kHz |
| 电流 - 输出： | 2A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 标准包装 |
| 供应商设备封装： | 8-SOICN |
| 产品目录页面： | 1216 (CN2011-ZH PDF) |
| 其它名称： | FAN8303MXDKR |
Functional Description
? ?
?
? 1 ? OUT
L =
V OUT V
?
?
f S ? Δ I L
The FAN8303 is a monolithic, non-synchronous,
current-mode, step-down regulator with internal power
MOSFETs. It achieves 2A continuous output current
over a wide input supply range from 5V to 23V with
excellent load and line regulation. The output voltage
can be regulated as low as 0.6V. The FAN8303 uses
current-mode operation that provides fast transient
response and eases loop stabilization. The FAN8303
requires a minimum number of readily available
standard external components.
Current Mode PWM Control Loop
FAN8303 uses current-mode PWM control scheme.
The peak inductor current is modulated in each
switching cycle by an internal op-amp output signal to
achieve the output voltage regulation. An internal slope
compensation circuit is included to avoid sub-harmonic
Inductor Selection
A higher inductor value lowers ripple current. The
inductor value can be calculated as:
(1)
? V IN ?
where:
f s is the switching frequency;
V OUT is the output voltage;
V IN is the input supply voltage; and
Δ I L Is the inductor ripple current.
Considering worst case, the equation is changed to:
? 1 ? V OUT
?
?
?
oscillation at duty cycle greater than 50%. Current-
mode control provides cycle-by-cycle current limit
protection and superior regulation control loop response
compared to the traditional voltage-mode control.
L =
V OUT
f S ? Δ I L , MAX
?
? V IN , MAX
?
?
(2)
In normal operation, the high-side MOSFET is turned on
Δ V OUT ? Δ I L ? ? ESR +
?
?
8 ? C OUT ? f S
at the beginning of each switching cycle, which causes
the current in the inductor to build up. The current-
control loop senses the inductor current by sensing the
voltage across the high-side senseFET during on time.
The output of the current-sense amplifier is summed
with the slope compensation signal and the combined
signal is compared with the error amplifier output to
generate the PWM signal. As the inductor current
ramps up to the controlled value, the high-side
MOSFET is turned off and the inductor current reaches
zero through a freewheeling diode. In light-load
condition, the high-side switch may be kept off for
several cycles to improve efficiency.
Short-Circuit Protection
The FAN8303 protects output short circuit by switching
frequency fold-back. The oscillator frequency is reduced
to about 45kHz when the output is shorted to ground.
This frequency fold-back allows the inductor current
more time to decay to prevent potential run-away
condition. The oscillator frequency switches to 370kHz
as V OUT rises gradually from 0V back to regulated level.
Input Capacitor Selection
To prevent high-frequency switching current passing to
the input, the input capacitor impedance at the
switching frequency must be less than input source
impedance. High-value, small, inexpensive, lower-ESR
ceramic capacitors are recommended. 10μF ceramic
capacitors should be adequate for 2A applications.
Output Capacitor Selection
A larger output capacitor value keeps the output ripple
voltage smaller. The formula of output ripple Δ V OUT is:
? 1 ?
(3)
? ?
where C OUT is the output capacitor and ESR is the
equivalent series resistance of the output capacitor.
Output Voltage Programming
The output voltage is set by a resistor divider, according
to the following equation:
V OUT = 0 . 6 ? 1 +
?
Slope Compensation and Inductor Peak
Current
The slope compensation provides stability in constant
?
?
R 2 ?
R 3 ?
(4)
frequency architecture by preventing sub-harmonic
oscillations at high duty cycles. It is accomplished
internally by adding a compensating ramp to the
inductor current signal at duty cycles in excess of 50%.
Maximum Load Current at Low V IN
The FAN8303 is able to operate with input supply
voltage as low as 5V, although the maximum allowable
output current is reduced as a function of duty cycle
(see Figure 15) . Additionally, at this low input voltage; if
the duty cycle is greater than 50%, slope compensation
reduces allowable output current.
? 2008 Fairchild Semiconductor Corporation
FAN8303 ? Rev. 1.0.0
8
Freewheeling Diode
An output freewheeling diode carries load current when
the high-side switch is turned off. Therefore, use a
Schottky diode to reduce loss due to diode forward
voltage and recovery time. The diode should have at
least 2A current rating and a reverse blocking voltage
greater than the maximum input voltage. The diode
should be close to the SW node to keep traces short
and reduce ringing.
www.fairchildsemi.com
相关PDF资料 |
PDF描述 |
|---|---|
| FCM8201QY | IC CTLR DC MOTOR BLDC 3PH 32LQFP |
| FCM8202QY | IC BLDC MOTOR CTLR 3PH 32-LQFP |
| FDC6323L | IC LOAD SWITCH INT 8VIN SSOT-6 |
| FDC6324L | IC LOAD SWITCH INT 20VIN SSOT-6 |
| FDC6325L | IC LOAD SWITCH INT 8VIN SSOT-6 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| FAN8303MX-CUT TAPE | 制造商:FAIRCHILD 功能描述:FAN8303 Series 2 A 23 V Non-Synchronous Step-Down DC/DC Regulator - SOIC-8 |
| FAN8400BD3 | 功能描述:马达/运动/点火控制器和驱动器 BLDC Motor Driver 3 Phase RoHS:否 制造商:STMicroelectronics 产品:Stepper Motor Controllers / Drivers 类型:2 Phase Stepper Motor Driver 工作电源电压:8 V to 45 V 电源电流:0.5 mA 工作温度:- 25 C to + 125 C 安装风格:SMD/SMT 封装 / 箱体:HTSSOP-28 封装:Tube |
| FAN8400BD3TF | 功能描述:马达/运动/点火控制器和驱动器 BLDC Motor Driver 3 Phase RoHS:否 制造商:STMicroelectronics 产品:Stepper Motor Controllers / Drivers 类型:2 Phase Stepper Motor Driver 工作电源电压:8 V to 45 V 电源电流:0.5 mA 工作温度:- 25 C to + 125 C 安装风格:SMD/SMT 封装 / 箱体:HTSSOP-28 封装:Tube |
| FAN8400D | 制造商:FAIRCHILD 制造商全称:Fairchild Semiconductor 功能描述:3-Phase BLDC Motor Driver with PLL |
| FAN8400D3 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:DC Motor Controller/Driver |
发布紧急采购，3分钟左右您将得到回复。