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| 型号： | MAX1889ETE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 23/32页 |
| 文件大小： | 0K |
| 描述： | IC PWR SUP TRPL LCD 16-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 控制器，TFT LCD |
| 输入电压： | 2.7 V ~ 5.5 V |
| 输出数： | 3 |
| 输出电压： | 2.7 V ~ 13 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-WQFN 裸露焊盘 |
| 供应商设备封装： | 16-TQFN-EP（5x5） |
| 包装： | 带卷 (TR) |
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Triple-Output TFT LCD Power Supply
with Fault Protection
To avoid excessive voltage coupling, a small capacitor
can be added in parallel with the base resistor. The
resulting RC time constant should be between 5μs to
50μs.
Stability Requirements
3) A third pole is set by the linear regulator ’ s feedback
resistance and the capacitance (including stray
capacitance) between FB_ and GND (for the posi-
tive LDO) and FBN and GND (for the negative LDO)
(Figure 8):
The MAX1889 linear-regulator controllers use an inter-
nal transconductance amplifier to drive an external
pass transistor. The transconductance amplifier, the
pass transistor, the base-emitter resistor, and the out-
put capacitor determine the loop stability. If the output
capacitor and pass transistor are not properly selected,
f POLE ( FB )_ POS =
f POLE ( FB )_ NEG =
1
2 π C FB ( R 12 II R 13 )
1
2 π C FB ( R 9 II R 10 )
? ? 1 + ?
A V ( LDO ) = ?
?
the linear regulator can be unstable.
The transconductance amplifier regulates the output
voltage by controlling the pass transistor ’ s base cur-
rent. The total DC loop gain is approximately:
? 5 . 5 ? ? ? I h ? ?
BIAS FE ? V REF
? ?
? V T ? ? ? I LOAD ? ?
4) If the second and third poles occur well after unity-
gain crossover, the linear regulator remains stable:
f POLE ( CBE ) > 2 f POLE ( CLDO ) A V ( LDO )
However, if the ESR zero occurs before the unity-gain
crossover, cancel the zero with the feedback pole by
changing circuit components such that:
where V T is 26mV at room temperature, and I BIAS is the
current through the base-to-emitter resistor (R BE ). This
bias resistor is typically 3k ? , providing 0.23mA of cur-
rent, biasing the LDO near its regulation voltage setpoint.
f POLE ( FB ) ≈
1
2 π C OUT R ESR
The output capacitor and the load resistance create the
dominant pole in the system. The pass transistor ’ s input
capacitance creates a second pole in the system.
Additionally, the output capacitor ’ s ESR generates a zero.
To achieve stable operation, use the following equations
to verify that the linear regulator is properly compensated:
1) First, determine the dominant pole set by the linear
regulator ’ s output capacitor and the load resistor:
For most applications where ceramic capacitors are
used, the ESR zero always occurs after the crossover.
A capacitor connected between the output and the
feedback node improves the transient response,
reduces the noise coupled into the feedback loop, and
maintains the correct regulation point (Figure 8).
Output Capacitor Selection
Typically, more output capacitance provides the best
solution, since this also reduces the output voltage drop
f POLE ( CLDO ) =
1
2 π C LDO R LOAD
=
I LOAD ( MAX )
2 π C LDO V LDO
immediately after a load transient. Connect at least a
0.1μF capacitor between the linear regulator ’ s output and
ground, as close to the external pass transistor as possi-
The unity gain crossover of the linear regulator is:
f CROSSOVER = A V(LDO) f POLE(CLDO)
2) Next, determine the second pole set by the base-
to-emitter capacitance (including the transistor ’ s
input capacitance), the transistor ’ s input resistance,
and the base-to-emitter pullup resistor:
ble. Depending on the selected pass transistor, larger
capacitor values may be required for stability (see the
Stability Requirements section). Furthermore, the output
capacitor ’ s ESR affects stability. Use output capacitors
with an ESR less than 200m ? to ensure stability and opti-
mum transient response. Once the minimum capacitor
value for stability is determined, verify that the linear regu-
lator ’ s output does not contain excessive noise. Although
f POLE ( CBE ) =
=
1
2 π C BE ( R BE II R IN )
R BE I LOAD + V T h FE
2 π C BE R BE V T h FE
adequate for stability, small capacitor values can provide
too much bandwidth, making the linear regulator sensitive
to noise. Larger capacitor values reduce the bandwidth,
thereby reducing the regulator ’ s noise sensitivity. If noise
on the ground reference causes the design to be margin-
ally stable for the negative linear regulator, bypass the
negative output back to its reference voltage. This tech-
nique reduces the differential noise on the output.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1889EVKIT | 功能描述:电源管理IC开发工具 MAX1889 Eval Kit RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MAX188ACAP | 功能描述:模数转换器 - ADC Integrated Circuits (ICs) RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX188ACAP+ | 功能描述:模数转换器 - ADC 12-Bit 8Ch 133ksps 5.25V Precision ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX188ACAP+T | 功能描述:模数转换器 - ADC 12-Bit 8Ch 133ksps 5.25V Precision ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
| MAX188ACAP-T | 功能描述:模数转换器 - ADC RoHS:否 制造商:Texas Instruments 通道数量:2 结构:Sigma-Delta 转换速率:125 SPs to 8 KSPs 分辨率:24 bit 输入类型:Differential 信噪比:107 dB 接口类型:SPI 工作电源电压:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-32 |
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