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参数资料
| 型号： | MAX5975BETE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 13/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK ISO CM 16TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 600kHz |
| 占空比： | 84% |
| 电源电压： | 12 V ~ 24 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 16-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
Current-Mode PWM Controllers with Frequency
Dithering for EMI-Sensitive Power Supplies
Because the MAX5975B is designed for use with low-
V S
R IN
IN
voltage power sources such as wall adapters outputting
12V to 24V, it has a lower UVLO wakeup threshold of 10V.
Startup Operation
The device starts up when the voltage at IN exceeds 20V
(MAX5975A) or 10V (MAX5975B) and the enable input
voltage is greater than 1.26V.
R EN1
C IN
MAX5975
During normal operation, the voltage at IN is normally
derived from a tertiary winding of the transformer.
However, at startup there is no energy being deliv-
ered through the transformer; hence, a special boot-
strap sequence is required. In the Typical Applications
DIGITAL
CONTROL
N
R EN2
EN
Circuits , C IN charges through the startup resistor, R IN , to
an intermediate voltage. Only 100 F A of the current sup-
plied through R IN is used by the ICs, the remaining input
current charges C IN until V IN reaches the bootstrap
UVLO wakeup level. Once V IN exceeds this level, NDRV
begins switching the n-channel MOSFET and transfers
energy to the secondary and tertiary outputs. If the volt-
age on the tertiary output builds to higher than 7V (the
bootstrap UVLO shutdown level), then startup has been
Figure 1. Programmable UVLO for the Power Source
V S
R IN
IN
accomplished and sustained operation commences.
If V IN drops below 7V before startup is complete, the
device goes back to low-current UVLO. In this case,
increase the value of C IN to store enough energy to allow
the voltage at the tertiary winding to build up.
Soft-Start
A capacitor from SS to GND, C SS , programs the soft-
start time. V SS controls the oscillator duty cycle during
startup to provide a slow and smooth increase of the
duty cycle to its steady-state value. Calculate the value
of C SS as follows:
C SS = SS-CH SS
C IN
DIGITAL
CONTROL
N
EN
MAX5975
I × t
2V
where I SS-CH (10 F A typ) is the current charging C SS dur-
ing soft-start and t SS is the programmed soft-start time.
A resistor can also be added from the SS pin to GND to clamp
V SS < 2V and, hence, program the maximum duty cycle to be
less than 80% (see the Duty-Cycle Clamping section).
n-Channel MOSFET Gate Driver
The NDRV output drives an external n-channel MOSFET.
NDRV can source/sink in excess of 650mA/1000mA peak
current; therefore, select a MOSFET that yields acceptable
Figure 2. External Control of the Enable Input
conduction and switching losses. The external MOSFET
used must be able to withstand the maximum clamp voltage.
13
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相关代理商/技术参数 |
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| MAX5975CETE+ | 制造商:Maxim Integrated Products 功能描述:CURRENT-MODE PWM CONTROLLERS WITH FREQUENCY DITHERING FOR EM - Rail/Tube |
| MAX5975DETE+ | 制造商:Maxim Integrated Products 功能描述:CURRENT-MODE PWM CONTROLLERS WITH FREQUENCY DITHERING FOR EM - Rail/Tube |
| MAX5976AETE+ | 功能描述:热插拔功率分布 2.7-18V Hot-Swap Controller RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| MAX5976AETE+T | 功能描述:热插拔功率分布 2.7-18V Hot-Swap Controller RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
| MAX5976BETE+ | 功能描述:热插拔功率分布 2.7-18V Hot-Swap Controller RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube |
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