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参数资料
| 型号： | MAX774EPA+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR INV PWM 8-DIP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| PWM 型： | 控制器 |
| 输出数： | 1 |
| 频率 - 最大： | 300kHz |
| 占空比： | 85% |
| 电源电压： | 3 V ~ 16.5 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 是 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 8-DIP（0.300"，7.62mm） |
| 包装： | 管件 |
-5V/-12V/-15V or Adjustable, High-Efficiency,
Low I Q Inverting DC-to-DC Controllers
R Z
0.1 μ F
V OUT
EXT Drive Voltages
EXT swings from OUT to V+ and provides the drive out-
put for an external power MOSFET. When using the on-
chip feedback resistors for the preset output voltages,
the voltage at OUT equals the output voltage. When
R2
R1
1
2
OUT
FB
MAX774
MAX775
MAX776
GND
8
using external feedback resistors, OUT may be tied to
GND or some other potential between V OUT and GND.
Always observe the V+ to OUT absolute maximum rat-
ing of 21V. For V+ to output differentials greater than
21V, OUT must be tied to a potential more positive than
the output and, therefore, the output voltage must be
0.1 μ F
4
REF
set with an external resistor divider.
In nonbootstrapped operation with low input voltages
(<4V), tie OUT to a negative voltage to fully enhance the
___ = _______
6V ≤ V Z + V IN ≤ 10V
? VOUT ? – V Z
> I Z
R Z
I Z = ZENER BREAKDOWN CURRENT
V Z = ZENER BREAKDOWN VOLTAGE
V IN = INPUT SUPPLY VOLTAGE
Figure 5. Connection Using Zener Diode to Boost Base Drive
connected to the output voltage (-5V, -12V, -15V). In
nonbootstrapped operation, OUT is connected to
ground, and EXT now swings from V+ to ground.
At high input-to-output differentials, it may be neces-
sary to use nonbootstrapped mode to avoid the 21V V+
to V OUT maximum rating. Also, observe the V GS maxi-
mum rating of the external transistor. At intermediate
voltages and currents, the advantages of bootstrapped
vs. nonbootstrapped operation are slight. When input
voltages are less than about 4V, always use the boot-
strapped circuit.
Shutdown and Quiescent Current
The MAX774/MAX775/MAX776 are designed to save
power in battery-powered applications. A TTL/CMOS
logic-level shutdown input (SHDN) has been provided
for the lowest-power applications. When shut down
(SHDN = V+), most internal bias current sources and
the reference are turned off so that less than 5μA of
current is drawn.
In normal operation, the quiescent current will be less
than 100μA. However, this current is measured by forc-
ing the external switch transistor off. Even with no load,
in an actual application, additional current will be
drawn to supply the feedback resistors’ and the diode’s
and capacitor’s leakage current. Under no-load condi-
tions, you should see a short current pulse at half the
peak current approximately every 100ms (the exact
period depends on actual circuit leakages).
external MOSFET. Accomplish this by creating an inter-
mediate voltage for V OUT with a zener diode (Figure 5).
__________________Design Procedure
Setting the Output Voltage
The MAX774/MAX775/MAX776 are preset for -5V, -12V,
and -15V output voltages, respectively; however, they
may also be adjusted to other values with an external
voltage divider. For the preset output voltage, connect
FB to REF and connect OUT to the output (Figure 3). In
this case, the output voltage is sensed by OUT.
For an adjustable output (Figures 3 and 4), connect an
external resistor divider from the output voltage to FB,
and from FB to REF. In this case, the divided-down out-
put voltage is sensed via the FB pin.
There are three reasons to use the external resistor divider:
1) An output voltage other than a preset value is
desired.
2) The input-to-output differential exceeds 21V.
3) The output voltage (V OUT to GND) exceeds -15V.
See Figures 3 and 4 for adjustable operation. The
impedance of the feedback network should be low
enough that the input bias current of FB is not a factor.
For best efficiency and precision, allow 10μA to flow
through the network. Calculate (V REF - V FB ) / R1 =
10μA. Since V REF = 1.5V and V FB = 0V, R1 becomes
150k ? . Then calculate R2 as follows:
R2 V OUT
R1 V REF
V OUT
(or, ______ = 10 μ A)
R2
Choosing an Inductor
Practical inductor values range from 10μH to 50μH.
The maximum inductor value is not particularly critical.
For highest current at high ? V OUT ? to V+ ratios, the
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX774EPA+ | 功能描述:DC/DC 开关控制器 5/12/15/AdjV- Inv DC/DC Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX774ESA | 功能描述:DC/DC 开关控制器 5/12/15/AdjV- Inv DC/DC Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX774ESA+ | 功能描述:DC/DC 开关控制器 5/12/15/AdjV- Inv DC/DC Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX774ESA+T | 功能描述:DC/DC 开关控制器 5/12/15/AdjV- Inv DC/DC Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX774ESA-T | 功能描述:DC/DC 开关控制器 5/12/15/AdjV- Inv DC/DC Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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