收藏本站
Wide-Input, High-Frequency, Triple-Output Supplies
with Voltage Monitor and Power-On Reset
? 1 . 3 × 2 π × C R ,
BW MAX = MIN ?
?
?
?
β ( MIN ) =
A third pole occurs due to the input capacitance of the
NMOS transistor ’s gate, C q (C iss from the MOSFET
data sheet), and the compensation resistor (R A ). If an
NPN bipolar transistor is used instead, this third pole
can be calculated from the base capacitance (C q =
C IBO from the NPN data sheet). To ensure stability, a
zero is added to the loop from the resistor (R A ) and
capacitor (C A ).
For good stability and transient response, first pick
C OUT2 at approximately 6.8μF/A of load current. For the
Typical Applications Circuit , C OUT2 is a 10μF ceramic
capacitor. Ensure that the zero formed from the ESR of
C OUT2 is greater than the maximum bandwidth BW MAX
(calculated below). The maximum bandwidth should
also be less than the pole created by Q3’s gate capaci-
tance (Cq) and the compensation resistor (R A ).
? 1 1 ?
?
G C
? 1 1 ?
×
? ?
? 10 2 π × R ESR _ COUT 2 C OUT ?
The following equations set the compensation zero a
decade and a half below the maximum load pole and
ensure the above constraint is met. Choose the larger
of the two values for C A .
drive current. The selected MOSFET must have the gate
threshold voltage meet the following criteria:
V GS _ MAX ≤ V DRV 2 - V OUT 2
where V DRV2 is equal to 7.75V or V SUP2 - 1.5V
(whichever is less), and V GSMAX is the maximum gate
voltage required to yield the on-resistance specified by
the manufacturer’s data sheet. Logic-gate MOSFETs
are recommended.
NPN-Transistor Selection
The MAX8513/MAX8514s’ OUT2 can use a less expen-
sive NPN transistor as the series pass transistor. In
selecting the appropriate NPN transistor, make sure the
beta is large enough so the regulator can provide
enough base current. The minimum beta of the transis-
tor is:
I OUT 2(MAX )
4 mA
In addition, to avoid premature dropout, V CE_SAT ≤
V IN_MIN - V OUT2 .
OUT3_ Transistor Selection
The pass transistors must meet specifications for cur-
rent gain ( β ), input capacitance, collector-emitter satu-
ration voltage, and power dissipation. The transistor’s
8 × V OUT OUT q C 2 × g C ( MAX ) ×
× C
× C × G
( )
g C ( MAX ) × R ESR _ COUT 2 + 1
13 ×
g C ( MAX ) V OUT 2 + I OUT 2 ( MAX )
? 16 10 ×
(
)
g C ( MAX ) V OUT 2 + I OUT 2 ( MAX )
? ? ESR _ COUT 2 OUT ? C q
I OUT 3 P = ? I DRV 3 P _ MIN - - BE ? β
R A = 10 10 × ×
?
?
?
?
?
?
C A = MAX ?
?
? G C 2 × g C ( MAX )
?
? R C
V OUT 2 C OUT 2
C A
( g C ( MAX ) × R ESR _ COUT 2 + 1 )
( g C ( MAX ) V OUT 2 + I OUT 2 ( MAX ) )
×
,
current gain limits the guaranteed maximum output cur-
rent to:
? V ?
? R12 ?
where I DRV3P_MIN is the minimum base-drive current
and R12 is the pullup resistor connected between the
transistor ’s base and emitter (see the Typical
Applications Circuits ). In addition, to avoid premature
dropout V CE_SAT ≤ V IN_MIN - V OUT3 . Furthermore, the
transistor’s current gain increases the linear regulator’s
DC loop gain (see the Stability Requirements section),
so excessive gain destabilizes the output. Therefore,
transistors with current gain over 100 at the maximum
output current, such as Darlington transistors, are not
recommended. The transistor’s input capacitance and
input resistance also create a second pole, which could
be low enough to destabilize the LDO when the output
MOSFET Transistor Selection
MAX8513/MAX8514s’ OUT2 uses N-channel MOSFETs
as the series pass transistor to improve efficiency for
high output current by not requiring a large amount of
is heavily loaded.
The transistor’s saturation voltage at the maximum output
current determines the minimum input-to-output voltage
differential that the linear regulator supports. Alternately,
28
______________________________________________________________________________________
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
MAX8552EUB+ IC DRIVER MOSFET HS 10-UMAX
MAX8595XETA+T IC LED DRIVR WHITE BCKLGT 8-TDFN
MAX8607ETD+T IC LED DRIVR PHOTO FLASH 14-TDFN
MAX8608YETD+T IC LED DRVR WT/OLED BCKLT 14TDFN
MAX8631XETI+T IC LED DRVR WHITE BCKLGT 28-TQFN
MAX8645YETI+T IC LED DRVR WHITE BCKLGT 28-TQFN
MAX8647ETE+T IC LED DRVR WT/RGB BCKLGT 16TQFN
MAX8702ETP+ IC DRVR MOSFET DUAL 20-TQFN
相关代理商/技术参数
MAX8514AEI 功能描述:DC/DC 开关控制器 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
MAX8514AEI-T 功能描述:DC/DC 开关控制器 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
MAX8514EEI 功能描述:DC/DC 开关控制器 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
MAX8514EEI-T 功能描述:DC/DC 开关控制器 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
MAX8515AEXK 制造商:Maxim Integrated Products 功能描述:WIDE-INPUT 0.6V SHUNT REGULATOR FOR - Rail/Tube 制造商:Rochester Electronics LLC 功能描述:
MAX8515AEXK+ 制造商:Maxim Integrated Products 功能描述:V-REF ADJUSTABLE 0.2V TO 18V 20MA 5PIN SC-70 - Rail/Tube
MAX8515AEXK+T 功能描述:基准电压& 基准电流 Shunt Regulator RoHS:否 制造商:STMicroelectronics 产品:Voltage References 拓扑结构:Shunt References 参考类型:Programmable 输出电压:1.24 V to 18 V 初始准确度:0.25 % 平均温度系数（典型值）:100 PPM / C 串联 VREF - 输入电压（最大值）: 串联 VREF - 输入电压（最小值）: 分流电流（最大值）:60 mA 最大工作温度:+ 125 C 封装 / 箱体:SOT-23-3L 封装:Reel
MAX8515AEXK-T 功能描述:基准电压& 基准电流 RoHS:否 制造商:STMicroelectronics 产品:Voltage References 拓扑结构:Shunt References 参考类型:Programmable 输出电压:1.24 V to 18 V 初始准确度:0.25 % 平均温度系数（典型值）:100 PPM / C 串联 VREF - 输入电压（最大值）: 串联 VREF - 输入电压（最小值）: 分流电流（最大值）:60 mA 最大工作温度:+ 125 C 封装 / 箱体:SOT-23-3L 封装:Reel