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| 型号： | MAX1997ETJ+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 25/31页 |
| 文件大小： | 0K |
| 描述： | IC PWR SUPPLY TFT LCD 32TQFN |
| 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： | 5 |
| 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： | 32-WFQFN 裸露焊盘 |
| 供应商设备封装： | 32-TQFN-EP（5x5） |
| 包装： | 带卷 (TR) |
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Quintuple/Triple-Output TFT LCD Power Supplies
with Fault Protection and VCOM Buffer
After including the effects of resistor tolerance, com-
parator offset, and input voltage variation, the minimum
input overcurrent threshold equation is:
If R5 =150k ? , then R4 = 39.2k ? . The typical overcur-
rent threshold is:
× ? 1 -
? = 4 . 15 A
V IN(MIN) ×
R 3 × ( 1 + ε )
R 2 × ( 1 + ε ) + R 3 × ( 1 + ε )
+
I TH_TYP =
3.3V
0.047 ?
? 1 50 ? × (39.2k ? +1 50 ? ) ?
? 150 ? × (51.1k ? +1 50 ? ) ?
5 mV = ( V IN(MIN) - I L(MAX) × R DS(MAX) ) ×
R 5 × ( 1 + ε )
R 4 × ( 1 + ε ) + R 5 × ( 1 + ε )
where V IN(MIN) is the minimum expected value of the
input voltage, ε is the tolerance of the resistors, and 5mV
is the worst-case input offset voltage of the comparator.
Charge Pumps
Selecting the Number of Charge-Pump Stages
For highest efficiency, always choose the lowest num-
ber of charge-pump stages that meet the output
requirement. The number of positive charge-pump
stages is given by:
k =
To simplify the equation, define a constant (k) as follows:
1 + ε
1 + ε
N POS =
V G_ON + V DROPOUT -V MAIN
V MAIN - 2 × V D
V IN(MIN) ×
+ 5 mV = ( V IN(MIN) -
I L(MAX) DS(MAX) ) ×
× R
The minimum threshold equation becomes:
R 3
k × R 2 + R 3
k × R 5
R 4 + k × R 5
Solving for R4/R5 yields:
where N POS is the number of positive charge-pump
stages, V G_ON is the positive linear-regulator (REG P)
output, V MAIN is the main step-up regulator output, V D
is the forward voltage drop of the charge-pump diode,
and V DROPOUT is the dropout margin for the linear reg-
ulator. Use V DROPOUT = 2V.
The number of negative charge-pump stages is given by:
= k × ?
? V IN(MIN)
+ 5 mV
?
-V G_OFF DROPOUT
N NEG =
R4
R5
?
? R 3 + k × R 2
R 3
? V IN(MIN) - I L(MAX) × R DS(MAX)
?
?
- 1 ?
?
+V
V MAIN - 2 × V D
where N NEG is the number of negative charge-pump
stages, V G_OFF is the negative linear-regulator (REG N)
The R4/R5 ratio guarantees the required minimum level
for I L(MAX) . The typical overcurrent threshold is given by:
output, V MAIN is the main step-up regulator output, V D
is the forward-voltage drop of the charge-pump diode,
× ? 1 -
R5 × (R2+R3) ?
I TH_TYP =
V IN(TYP)
R DS(TYP)
?
?
R3 × (R4 +R5) ?
?
and V DROPOUT is the dropout margin for the linear reg-
ulator. Use V DROPOUT = 2V.
The above equations are derived based on the
k = = 0 . 9802
= 0 . 9802 × ?
- 1 ?
?
? 2.7V ×
+ 0 . 005 V
N POS =
-V G_OFF DROPOUT IN
N NEG =
The following example shows how to apply the above
equations in the design. If 1% resistors are used, then
ε = 0.01. To set V OCP to be around 75% of V IN , select
R2 = 51.1k ? and R3 = 150k ? . Assume that the mini-
mum input voltage is 2.7V and the typical input voltage
is 3.3V, the average inductor current at maximum load
is 1.25A, and the maximum R DS(ON) of P1 is 100m ? :
1 - 0.01
1 + 0.01
? ?
R4 ? 2.7V - 1.25A × 0.1 ? ?
R5 150 ?
? 150 ? + 0 . 9802 × 51 . 1 k ? ?
= 0 . 2637
assumption that the first stage of the positive charge
pump is connected to V MAIN and the first stage of the
negative charge pump is connected to ground.
Sometimes fractional stages are more desirable for bet-
ter efficiency. This can be done by connecting the first
stage to V IN or another available supply. If the first
charge-pump stage is powered from V IN , then the
above equations become:
V G_ON + V DROPOUT -V IN
V MAIN - 2 × V D
+V +V
V MAIN - 2 × V D
______________________________________________________________________________________
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1997EVKIT | 制造商:Maxim Integrated Products 功能描述:QUINTUPLE/TRIPLE OUTPUT TFT LCD POWER SUPPLIE - Bulk |
| MAX19983A | 功能描述:上下转换器 RoHS:否 制造商:Texas Instruments 产品:Down Converters 射频:52 MHz to 78 MHz 中频:300 MHz LO频率: 功率增益: P1dB: 工作电源电压:1.8 V, 3.3 V 工作电源电流:120 mA 最大功率耗散:1 W 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PQFP-128 |
| MAX19985AETX+ | 功能描述:上下转换器 High-Gain 700MHz to 1GHz Downconv RoHS:否 制造商:Texas Instruments 产品:Down Converters 射频:52 MHz to 78 MHz 中频:300 MHz LO频率: 功率增益: P1dB: 工作电源电压:1.8 V, 3.3 V 工作电源电流:120 mA 最大功率耗散:1 W 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PQFP-128 |
| MAX19985AETX+T | 功能描述:上下转换器 High-Gain 700MHz to 1GHz Downconv RoHS:否 制造商:Texas Instruments 产品:Down Converters 射频:52 MHz to 78 MHz 中频:300 MHz LO频率: 功率增益: P1dB: 工作电源电压:1.8 V, 3.3 V 工作电源电流:120 mA 最大功率耗散:1 W 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PQFP-128 |
| MAX19985ETX+ | 功能描述:上下转换器 Dual, SiGe, .7-1GHz Downconversion Mixer RoHS:否 制造商:Texas Instruments 产品:Down Converters 射频:52 MHz to 78 MHz 中频:300 MHz LO频率: 功率增益: P1dB: 工作电源电压:1.8 V, 3.3 V 工作电源电流:120 mA 最大功率耗散:1 W 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:PQFP-128 |
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