- 您现在的位置：买卖IC网 > PDF目录1840 > MAX1802EHJ+ (Maxim Integrated Products)IC PWR SPLY STEP DOWN 32-TQFP PDF资料下载
参数资料
| 型号： | MAX1802EHJ+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 18/28页 |
| 文件大小： | 0K |
| 描述： | IC PWR SPLY STEP DOWN 32-TQFP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 360 |
| 应用： | 控制器，数字式相机 |
| 输入电压： | 2.5 V ~ 11 V |
| 输出数： | 5 |
| 输出电压： | 1.25 V ~ 5.5 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-TQFP |
| 供应商设备封装： | 32-TQFP（5x5） |
| 包装： | 托盘 |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页当前第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页
Digital Camera Step-Down
Power Supply
age lockout threshold. The internal core converter, aux-
iliary controllers, and MAX1801 slave controllers each
sink up to 30μA REF current during startup. If multiple
MAX1801 controllers are turned on simultaneously,
ensure that the master voltage reference can provide
sufficient current, or buffer the reference with an appro-
priate unity-gain amplifier.
Oscillator
The oscillator uses a comparator, a 100ns one-shot,
OSC
VL
R OSC
and an internal N-channel MOSFET switch in conjunc-
tion with an external timing resistor and capacitor to
generate the oscillator signal at OSC (Figure 4). The
capacitor voltage exponentially approaches VL from
zero with a time constant given by the R OSC C OSC
product when the switch is open, and the comparator
output becomes high when the capacitor voltage
reaches V REF (1.25V). At that time, the one-shot acti-
vates the internal MOSFET switch to discharge the
capacitor within a 100ns interval, and the cycle
repeats. Note that the oscillation frequency changes as
VL changes during startup. The oscillation frequency is
constant while the VL voltage is constant.
C OSC
V REF
(1.25V)
100ns
ONE-SHOT
MAX1802
Maximum Duty Cycle
The MAX1802 ’ s three auxiliary controllers use the saw-
tooth oscillator signal generated at OSC, the voltage at
DCON_, and an internal comparator to limit their maxi-
mum duty cycles (see Setting the Maximum Duty
Cycle ). Limiting the duty cycle can prevent saturation in
some magnetic components. A low maximum duty
cycle can also force the converter to operate in discon-
tinuous current mode, simplifying design stability at the
cost of a slight reduction in efficiency.
Soft-Start
All the MAX1802 converters feature a soft-start function
that limits inrush current and prevents excessive bat-
tery loading at startup by ramping the output voltage to
the regulation voltage. This is achieved by increasing
the internal reference inputs to the controller transcon-
ductance amplifiers from 0 to the 1.25V reference volt-
age over 1024 oscillator cycles when initial power is
applied or when the controller is enabled.
Overload Protection
The MAX1802 ’ s three auxiliary controllers have fault
protection that prevents damage to transformer-cou-
pled or SEPIC circuits due to an output overload condi-
tion. When the output voltage drops out of regulation
for 1024 oscillator clock periods, the auxiliary controller
is disabled to prevent excessive output current. Restart
the controller by cycling the voltage at ON_ or DCON_
to GND and back to the on state. For a step-up appli-
Figure 4. Oscillator
cation, short-circuit current is not limited, due to the DC
current path through the inductor and output rectifier to
the short circuit. If short-circuit protection is required in
a step-up configuration, use a protection device such
as a fuse to limit short-circuit current.
Design Procedure
Setting the Switching Frequency
Choose a switching frequency to optimize external
component size or circuit efficiency for the particular
MAX1802 application. Switching frequencies between
400kHz and 500kHz offer a good balance between
component size and circuit efficiency. Higher frequen-
cies allow smaller components, and lower frequencies
improve efficiency.
The switching frequency is set with an external timing
resistor (R OSC ) and capacitor (C OSC ). At the beginning
of a cycle, the timing capacitor charges through the
resistor until it reaches V REF . The charge time t 1 is:
t 1 = -R OSC (C OSC +10pF) In [1 - (V REF / V VL )]
Once the voltage at OSC reaches V REF , it discharges
through an internal switch over time t 2 = 200ns. The
oscillator frequency is f OSC = 1 / (t 1 + t 2 ). Set f OSC in
the range 100kHz ≤ f OSC ≤ 1MHz. Choose C OSC
between 47pF and 470pF. Determine R OSC from the
relation:
18
______________________________________________________________________________________
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1804EUB+ | IC FEEDBACK INTERGRATOR 10UMAX |
| MAX1806EUA18+ | IC REG LDO 1.8V/ADJ .5A 8-UMAX |
| MAX1809ETI+ | IC DDR TERMINATION 28-TQFN |
| MAX1810ESA | IC REG SMART CARD NETWORK 8-SOIC |
| MAX1811ESA+T | IC CHARGER USB LI+ 8-SOIC |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1802EHJ+ | 功能描述:直流/直流开关转换器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1802EHJ+T | 功能描述:直流/直流开关转换器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1802EHJ-T | 功能描述:直流/直流开关转换器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| MAX1804EUB | 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 |
| MAX1804EUB+ | 功能描述:电流和电力监控器、调节器 Feedback Integrator for Power Supply 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 |
发布紧急采购，3分钟左右您将得到回复。