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参数资料
| 型号： | MAX1865TEEP+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 21/25页 |
| 文件大小： | 0K |
| 描述： | IC PWR SUPPLY CONTROLLER 20QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 电源控制器 |
| 输入电压： | 4.5 V ~ 28 V |
| 电流 - 电源： | 1.4mA |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 20-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 20-QSOP |
| 包装： | 带卷 (TR) |
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
? POLE ( FB ) ≈
1
2 π C OUT R ESR
Do not use output capacitors with more than 200m Ω of
ESR. Typically, more output capacitance provides the
best solution, since this also reduces the output voltage
drop immediately after a load transient.
MAX1864
MAX1865
B_
FB_
C BE
R1
R2
R BE
Q PASS
C LDO
C BYP
V POS
V SUP
Linear Regulator Output Capacitors
Connect at least a 1μF capacitor between the linear
regulator ’s output and ground, as close to the
MAX1864/MAX1865 and external pass transistors as
possible. Depending on the selected pass transistor,
a) POSITIVE OUTPUT VOLTAGE
larger capacitor values may be required for stability
(see Stability Requirements ). Furthermore, the output
R4
V REF
capacitor’s ESR affects stability, providing a zero that
may be necessary to cancel the second pole. Use out-
put capacitors with an ESR less than 200m Ω to ensure
stability and optimum transient response.
Once the minimum capacitor value for stability is deter-
mined, verify that the linear regulator’s output does not
MAX1865
BF5
B5
C BE
R3
R BE
Q PASS
C NEG
V NEG
contain excessive noise. Although adequate for stabili-
ty, small capacitor values may provide too much band-
width, making the linear regulator sensitive to noise.
b) NEGATIVE OUTPUT VOLTAGE (MAX1865 ONLY)
C BYP
V SUP
Larger capacitor values reduce the bandwidth, thereby
reducing the regulator’s noise sensitivity.
If noise on the ground reference causes the design to
Figure 7. Base-Drive Noise Reduction
2 π ? POLE ( CBE ) ? ?
? - C IN ( Q )
be marginally stable for the negative linear regulator,
bypass the negative output back to its reference volt-
age (V REF , Figure 7). This technique reduces the differ-
C BE ≤
1 ? R BE I LOAD + V T h FE ?
R BE V T h FE ?
ential noise on the output.
Base-Drive Noise Reduction
The high-impedance base driver is susceptible to sys-
tem noise, especially when the linear regulator is lightly
loaded. Capacitively coupled switching noise or induc-
tively coupled EMI onto the base drive causes fluctua-
tions in the base current, which appear as noise on the
linear regulator’s output. Keep the base-drive traces
away from the step-down converter and as short as
possible to minimize noise coupling. Resistors in series
with the gate drivers (DH and DL) reduce the LX
switching noise generated by the step-down converter
(Figure 5). Additionally, a bypass capacitor may be
placed across the base-to-emitter resistor (Figure 7).
where C IN(Q) is the transistor’s input capacitance, and
f POLE(CBE) is the second pole required for stability.
Transformer Selection
In systems where the step-down controller’s output is
not the highest voltage, a transformer may be used to
provide additional postregulated, high-voltage outputs.
The transformer generates unregulated, high-voltage
supplies that power the positive and negative linear
regulators. These unregulated supply voltages must be
high enough to keep the pass transistors from saturat-
ing. For positive output voltages, connect the trans-
former as shown in figure 6 where the minimum turns
ratio (N) is determined by:
N POS ≥ ?
-1 ?
This bypass capacitor, in addition to the transistor’s
input capacitance, could bring in a second pole that
will destabilize the linear regulator (see Stability
? V LDO(POS) + V SAT + V DIODE
? V OUT
?
?
Requirements ). Therefore, the stability requirements
determine the maximum base-to-emitter capacitance:
where V SAT is the pass transistor’s saturation voltage
under full load. For negative output voltages (MAX1865
______________________________________________________________________________________
21
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1865UEEP | 功能描述:电流和电力监控器、调节器 RoHS:否 制造商:STMicroelectronics 产品:Current Regulators 电源电压-最大:48 V 电源电压-最小:5.5 V 工作温度范围:- 40 C to + 150 C 安装风格:SMD/SMT 封装 / 箱体:HPSO-8 封装:Reel |
| MAX1865UEEP-T | 功能描述:电流和电力监控器、调节器 RoHS:否 制造商:STMicroelectronics 产品:Current Regulators 电源电压-最大:48 V 电源电压-最小:5.5 V 工作温度范围:- 40 C to + 150 C 安装风格:SMD/SMT 封装 / 箱体:HPSO-8 封装:Reel |
| MAX1868EGL | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1868ETL | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1869EGL | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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