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参数资料
| 型号： | MAX5070AASA+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 15/22页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK DIV ISO 8SOIC |
| 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： | 1MHz |
| 占空比： | 97.5% |
| 电源电压： | 10.8 V ~ 25 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 是 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
High-Performance, Single-Ended, Current-Mode
PWM Controllers
R CS = CS
MAX5071A/MAX5071B/MAX5071C
Feedback
The MAX5071A/MAX5071B/MAX5071C are designed to
be used with either an external error amplifier when
designed into a nonisolated converter or an error ampli-
fier and optocoupler when designed into an isolated
power supply. The COMP input is level-shifted and
connected to the inverting terminal of the PWM com-
parator (CPWM). Connect the COMP pin to the output
of the external error amplifier for nonisolated design.
Pull COMP high externally to at least 5V (or VREF) and
connect the optocoupler transistor as shown in Figures
7 and 8. COMP can be used for soft-start and also as a
shutdown. See the Typical Operating Characteristics to
find the turn-off COMP voltage at different tempera-
tures. If the maximum external COMP voltage is below
4.9V, it may reduce the PWM current-limit threshold
below 1V. Use the following equation to calculate mini-
mum COMP voltage (V COMP ) required for a guaranteed
peak primary current (I P-P ):
V COMP = (3 x I P-P x R CS ) + 1.95V
where R CS is a current-sense resistor.
Oscillator
The oscillator frequency is adjusted by adding an
external capacitor and resistor at R T /C T (see R T and C T
in the Typical Application Circuits ). R T is connected
from R T /C T to the 5V reference (VREF) and C T is con-
nected from R T /C T to GND. VREF charges C T through
R T until its voltage reaches 2.8V. C T then discharges
through an 8.3mA internal current sink until C T ’s voltage
reaches 1.1V, at which time C T is allowed to charge
through R T again. The oscillator’s period will be the
sum of the charge and discharge times of C T . Calculate
the charge time as:
t C = 0.57 x R T x C T
The discharge time is then:
Reference Output
VREF is a 5V reference output that can source 20mA.
Bypass VREF to GND with a 0.1μF capacitor.
Current Limit
The MAX5070/MAX5071 include a fast current-limit com-
parator to terminate the ON cycle during an overload or a
fault condition. The current-sense resistor (R CS ), connect-
ed between the source of the MOSFET and GND, sets
the current limit. The CS input has a voltage trip level
(V CS ) of 1V. Use the following equation to calculate R CS :
V
I P ? P
I P-P is the peak current in the primary that flows through
the MOSFET. When the voltage produced by this current
(through the current-sense resistor) exceeds the current-
limit comparator threshold, the MOSFET driver (OUT) will
turn the switch off within 60ns. In most cases, a small RC
filter is required to filter out the leading-edge spike on the
sense waveform. Set the time constant of the RC filter at
50ns. Use a current transformer to limit the losses in the
current-sense resistor and achieve higher efficiency
especially at low input-voltage operation.
Synchronization (MAX5071A/MAX5071B)
SYNC
SYNC is a bidirectional input/output that outputs a syn-
chronizing pulse and accepts a synchronizing pulse
from other MAX5071A/MAX5071Bs (see Figures 7 and
9). As an output, SYNC is an open-drain p-channel
MOSFET driven from the internal oscillator and requires
an external pulldown resistor (R SYNC ) from between
500 ? and 5k ? . As an input, SYNC accepts the output
pulses from other MAX5071A/MAX5071Bs.
Synchronize multiple MAX5071A/MAX5071Bs by con-
necting their SYNC pins together. All devices connected
together will synchronize to the one operating at the
t D =
R T × C T × 10 3
4 . 88 × R T ? 1 . 8 × 10 3
highest frequency. The rising edge of SYNC will precede
the rising edge of OUT by approximately the discharge
time (t D ) of the oscillator (see the Oscillator section). The
The oscillator frequency will then be:
pulse width of the SYNC output is equal to the time
required to discharge the stray capacitance at SYNC
f OSC =
1
t C + t D
through R SYNC plus the C T discharge time t D . Adjust
R T /C T such that the minimum discharge time t D is 200ns.
For the MAX5070A/MAX5071A, the converter output
switching frequency (f SW ) is the same as the oscillator
frequency (f OSC ). For the MAX5070B/MAX5071B/
MAX5071C, the output switching frequency is 1/2 the
oscillator frequency.
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| MAX5070AAUA | 功能描述:电流型 PWM 控制器 Single-Ended RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX5070AAUA+ | 功能描述:电流型 PWM 控制器 Single-Ended RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX5070AAUA+T | 功能描述:电流型 PWM 控制器 Single-Ended RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX5070AAUA-T | 功能描述:电流型 PWM 控制器 Single-Ended RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX5070BAPA+ | 制造商:Maxim Integrated Products 功能描述:HIGH-PERFORMANCE, SINGLE-ENDED, CURRENT-MODE PWM CONTROLLERS - Rail/Tube |
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