- 您现在的位置：买卖IC网 > PDF目录1841 > MAX1956ETI+T (Maxim Integrated Products)IC REG CTRLR BUCK PWM VM 28-TQFN PDF资料下载
参数资料
| 型号： | MAX1956ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/22页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 28-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| PWM 型： | 电压模式 |
| 输出数： | 2 |
| 频率 - 最大： | 660kHz |
| 占空比： | 97% |
| 电源电压： | 1.6 V ~ 5.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 28-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
1.6V to 5.5V Input, 0.5% Accurate, Dual
180° Out-of-Phase Step-Down Controllers
Foldback Current Limit
Foldback current limit is used to reduce power dissipa-
tion during overload and short-circuit conditions. This is
accomplished by lowering the current-limit threshold as
the output voltage drops because of overload.
To use foldback current limit, connect one resistor
(R FOBK ) from ILIM_ to the corresponding output, and
connect another resistor (R ILIM ) from ILIM_ to GND. The
values of R ILIM and R FOBK are calculated as follows:
1) First, select the percentage of foldback (P FB ). This
percentage corresponds to the current limit when
V OUT equals zero, divided by the current limit when
V OUT equals its nominal voltage. Typical values are
15% to 30%. To solve for the resistor values, use the
following equations:
In this event, the main outputs and the internal boost
regulator are disabled. The boost regulator starts up
again once the voltage at IN rises above the UVLO
threshold.
Startup and Output Sequencing
The MAX1955/MAX1956 use a digital soft-start to
reduce input inrush current during startup. In soft-start,
the output voltage is ramped up by increasing the FB_
regulation voltage in 80 steps of 10mV. Total soft-start
time is typically 4.27ms.
Some power supplies exhibit soft regulation during soft-
start. If the MAX1955/MAX1956 are powered from such
a power supply and enabled at or before power-up, the
input voltage might dip below the UVLO threshold, and
the output might not soft-start properly. To avoid such
R FOBK =
P FB × V OUT
5 μ A ( 1 - P FB )
issues, enable the MAX1955/MAX1956 after the input
supply has stabilized or add an RC filter to the IN pin of
the IC as shown in Figure 6. The value of R20 is ~510 ? ,
and the value of capacitor C31 is from 1μF to 10μF,
(
)
6 . 67 × R DS ( ON ) × I VALLEY × ( 1 - P FB ) × R FOBK
R ILIM =
V OUT - 6 . 67 × R DS ( ON ) × I VALLEY × ( 1 - P FB )
2) Select P FB values that provide R ILIM greater than
zero.
Recovery from Overload
and Short Circuit
The MAX1955/MAX1956 do not recover to nominal out-
put voltage at heavy load (near full load) after an over-
load or short-circuit condition, but they might operate at
a voltage below the nominal output until the input
power or EN pin is cycled through the OFF state. If
automatic recovery is mandatory, without cycling EN or
input power, add an RC filter of 1 ? and 0.015μF at
LX_ ’ s pins, as shown in Figure 6. Doing so decreases
the efficiency by 2% to 3%, depending on the input
voltage, output voltage, and current.
AVDD Decoupling
Due to high switching frequency and tight output toler-
depending on the startup characteristic of the input
power supply. The capacitor value is chosen to provide
power to the IC (100μA max) and keep it from falling
below the UVLO threshold during the input power-
supply dip.
The outputs can be set to power up at the same time,
or output 1 can be set to power up first and power
down last. Connect SEQ to GND for simultaneous
power up/down. Connect SEQ to IN to make output 1
power up first and power down last. Figure 3 is a timing
diagram.
If there is a fault condition (such as a short circuit) on
output 1 causing its voltage to drop below 90% of its
nominal regulation voltage, and SEQ is connected to
IN, then output 2 shuts down. Once the fault is cleared,
allowing the voltage on output 1 to rise above 90% of
its nominal regulation voltage, output 2 soft-starts and
powers up again.
ance (±0.5%), decoupling between V DD and AV DD is
recommended. Connect a 10 ? resistor between V DD
and AV DD and a 0.47μF capacitor between AV DD and
GND. Place the capacitor as close to AV DD as possible.
Undervoltage Lockout (UVLO)
SEQ = GND
EN
OUT1
OUT2
SEQ = IN
When the voltage at IN drops below its undervoltage
lockout (UVLO) threshold (see the Electrical
4.27ms
4.27ms
4.27ms
4.27ms
Characteristics ), the MAX1955/MAX1956 determine
that the input supply voltage is too low to power the IC.
Figure 3. Timing Diagram
12
______________________________________________________________________________________
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1961EEP+ | IC REG CTRLR BUCK PWM VM 20-QSOP |
| MAX1964TEEE+ | IC POWER CTRLR/SEQUENCER 16QSOP |
| MAX1967EUB+T | IC REG CTRLR BUCK PWM VM 10-UMAX |
| MAX1969EUI+T | IC DRVR POWER 28-TSSOP |
| MAX1971EEE+T | IC REG BUCK SYNC 0.75A DL 16QSOP |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1957EUB | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1957EUB+ | 功能描述:电流型 PWM 控制器 High-f Current-Mode PWM Buck Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1957EUB+T | 功能描述:电流型 PWM 控制器 High-f Current-Mode PWM Buck Controller RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1957EUB-T | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX19586ETN | 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 |
发布紧急采购，3分钟左右您将得到回复。