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参数资料
| 型号： | MAX1774EEI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 19/21页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ DL 28QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 1 V ~ 5.5 V |
| 输入电压： | 2.7 V ~ 28 V |
| 频率 - 开关： | 1.25MHz |
| 电流 - 输出： | 1.5A，2A |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 28-QSOP |
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
Inductor Selection
The essential parameters for inductor selection are
inductance and current rating. The MAX1774 operates
with a wide range of inductance values.
Calculate the inductance value for either CORE or
MAIN, L MIN :
L (MIN) = (V IN - V OUT ) ? (t ON(MIN) / l RIPPLE )
where t ONMIN is typically 400ns, and l RIPPLE is the con-
tinuous conduction peak-to-peak l RIPPLE current.
In continuous conduction, l RIPPLE should be chosen to
be 30% of the maximum load current. With high induc-
tor values, the MAX1774 begins continuous-conduction
operation at a lower fraction of full load (see Detailed
Description ).
The inductor’s saturation current must be greater than
the peak switching current to prevent core saturation.
Saturation occurs when the inductor’s magnetic flux
density reaches the maximum level the core can sup-
port and inductance starts to fall. The inductor heating
current rating must be greater than the maximum load
current to prevent overheating. For optimum efficiency,
the inductor series resistance should be less than the
current-sense resistance.
Capacitor Selection
Choose the output filter capacitors to service input and
output ripple current with acceptable voltage ripple.
ESR in the output capacitor is a major contributor to
Also, ensure that the tantalum capacitors’ surge-current
ratings exceed the startup inrush and peak switching
currents.
The input filter capacitor reduces peak currents drawn
from the power source and reduces noise and voltage
ripple at IN, caused by the circuit’s switching. Use a
low-ESR capacitor. Two smaller value low-ESR capaci-
tors can be connected in parallel if necessary. Choose
input capacitors with working voltage ratings higher
than the maximum input voltage.
MOSFET Selection
The MAX1774 drives an external enhancement-mode P-
channel MOSFET and a synchronous-rectifier N-channel
MOSFET. When selecting the MOSFETs, important para-
meters to consider are on-resistance (R DS(ON) ), maxi-
mum drain-to-source voltage (V DS(MAX) ), maximum
gate-to-source voltage (V GS(MAX) ), and minimum
threshold voltage (V TH(MIN) ).
Chip Information
TRANSISTOR COUNT: 4545
PROCESS: BiCMOS
Pin Configurations (continued)
TOP VIEW
output ripple. For the main converter, low-ESR capaci-
tors such as polymer or ceramic capacitors are recom-
mended. For the core converter, choosing a low-ESR
tantalum capacitor with enough ESR to generate about
1% ripple voltage across the output is helpful in ensur-
ing stability.
SHDNM 1
SHDNC 2
BKUP 3
MDRV 4
PGNDC 5
28 LXC
27 INS
26 LBO
25 ACO
24 INC
Voltage ripple is the sum of contributions from ESR and
the capacitor value:
V RIPPLE ≈ V RIPPLE,ESR + V RIPPLE,C
For tantalum capacitors, the ripple is determined mostly
by the ESR. Voltage ripple due to ESR is:
V RIPPLE,ESR ≈ (R ESR ) ? I RIPPLE
For ceramic capacitors, the ripple is mostly due to the
capacitance. The ripple due to the capacitance is
approximately:
V RIPPLE,C ≈ L I RIPPLE 2 C OUT V OUT
where V OUT is the average output voltage.
PGND 6
NDRV 7
CVL 8
IN 9
PDRV 10
CVH 11
LXB 12
BIN 13
BKOFF 14
MAX1774
28 QSOP
23 GND
22 FBC
21 CS-
20 CS+
19 FBM
18 REF
17 LBI
16 DBI
15 ACI
These equations are suitable for initial capacitor selec-
tion. Final values should be set by testing a prototype
or evaluation kit. When using tantalum capacitors, use
good soldering practices to prevent excessive heat
from damaging the devices and increasing their ESR.
______________________________________________________________________________________
19
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1774EGJ | 制造商:Maxim Integrated Products 功能描述: |
| MAX1774EMJ | 功能描述:直流/直流开关转换器 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 |
| MAX1774EVKIT | 功能描述:直流/直流开关转换器 Evaluation Kit for the MAX1774 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 |
| MAX1775EEE | 功能描述:直流/直流开关转换器 Dual-Out Step-Down for PDA/Palmtop 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 |
| MAX1775EEE+ | 功能描述:直流/直流开关转换器 Dual-Out Step-Down for PDA/Palmtop 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 |
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