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参数资料
| 型号： | MAX724CCK |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 10/13页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG ADJ TO220-5 |
| 标准包装： | 50 |
| 类型： | 降压（降压），升压（升压），反相，回扫 |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 2.5 V ~ 35 V |
| 输入电压： | 8 V ~ 40 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 100kHz |
| 电流 - 输出： | 5A |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 通孔 |
| 封装/外壳： | TO-220-5 |
| 包装： | 管件 |
| 供应商设备封装： | TO-220-5 |
5A/2A Step-Down, PWM,
Switch-Mode DC-DC Regulators
V OUT R2
Be sure that the selected capacitor can handle the ripple
current over the required temperature range. Also locate
the input capacitor very close to the MAX724/MAX726 and
use minimum length leads (surface-mount or radial
through-hole types). In most applications, ESR is more
important than actual capacitance value since electrolytic
capacitors are mostly resistive at the MAX724/MAX726's
100kHz switching frequency.
__________Applications Information
Setting Output Voltage
R1 and R2 set output voltage as follows:
R1 = -R2
2.21V
2.21V is the reference voltage, so setting R2 to 2.21k ?
(standard 1% resistor value) results in 1mA flowing
through R1 and R2 and simplifies the above equation.
Other values will also work for R2, but should not
exceed 4k ? .
Synchronizing the Oscillator
The MAX724/MAX726 can be synchronized to an exter-
nal 110kHz to 160kHz source by pulsing the V C pin to
ground at the desired clock rate. This is conveniently
done with the collector of an external grounded-emitter
NPN transistor. V C should be pulled low for 300ns.
Doing this may have some impact on output regulation,
but the effect should be minimal for compensation
resistor values between 1k ? and 4k ? .
Power Dissipation
The MAX724/MAX726 draw about 7.5mA operating cur-
rent, which is largely independent of input voltage or
load current. They draw an additional 5mA during
switch on-time. Power dissipated in the internal V SW
transistor is proportional to load current and depends
rent and voltage appear across the switch at the same
time. t SW is approximately: [50ns + (3ns/A) (I OUT )] for
the MAX724.
Power dissipation in the MAX726 can be estimated in
exactly the same way as the MAX724, except that 1.1V
(and not 1.8V) is a more reasonable value for the nomi-
nal voltage drop across the on-board power switch.
Ground Connections
GND demands a short low-noise connection to ensure
good load regulation. Since the internal reference is
referred to GND, errors in the GND pin voltage get mul-
tiplied by the error amplifier and appear at the output.
If the MAX724/MAX726 GND pin is separated from the
negative side of the load, then high load return current
can generate significant error across a seemingly small
ground resistance. Single-point grounding is the most
effective way to eliminate these errors. A recommend-
ed ground arrangement is shown in Figure 4.
Overload Protection
The V SW current is internally limited to about 6.5A in the
MAX724 and 2.6A in the MAX726. In addition, another
feature of the MAX724/MAX726's overload protection
scheme is that the oscillator frequency is reduced
when the output voltage falls below approximately half
its regulated value. This is the case during short-circuit
and heavy overload conditions.
Since the minimum on-time for the switch is about
0.6 μ s, frequency reduction during overload ensures
that switch duty cycle can fall to a low enough value to
maintain control of output current. At the normal
100kHz switching frequency, an on-time as short as
on both conduction losses (product of switch on-volt-
age and switch current) and dynamic switching losses
(due to switch rise and fall times). Total MAX724 power
dissipation can be calculated as follows:
MAX724
MAX726 FB
R1
P = V IN [7.5mA + 5mA (DC) + 2 I OUT t SW f OSC ] + . . .
. . . DC [I OUT (1.8V) + 0.1 ? (I OUT ) 2 ]
V OUT + 0.5V
DC = Duty Cycle =
V IN - 2V
t SW = Overlap Time = 50ns + (3ns/A) I OUT
HIGH CURRENT
RETURN PATH
GND
R2
NEGATIVE OUTPUT
NODE WHERE LOAD
REGULATION WILL
BE MEASURED
where t SW is "overlap" time. Switch dissipation is
momentarily high during overlap time because both cur-
Figure 4. Recommended Ground Connection
_______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX724CCM | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Current-Mode SMPS Controller |
| MAX724CKS | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Current-Mode SMPS Controller |
| MAX724ECK | 功能描述:直流/直流开关调节器 RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX724ECK-SL | 功能描述:直流/直流开关调节器 RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| MAX724ECM | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Current-Mode SMPS Controller |
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