- 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： | 18/22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
P HSSW = V IN × I LOAD × f SW ×
L PAR =
( 2 π f R )
× C PAR
Use R DS(ON) at T J(MAX) .
Q GS + Q Gd
I GATE
where I GATE is the average DH driver output-current
determined by:
1
2
The resistor for critical dampening (R SNUB ) is equal to 2 π
x f R x L PAR . Adjust the resistor value up or down to tailor
the desired damping and the peak voltage excursion.
I GATE ( ON ) =
2 . 5
R DH + R GATE
The capacitor (C SNUB ) should be at least 2 to 4 times
the value of the C PAR in order to be effective. The
power loss of the snubber circuit is dissipated in the
P HSDR G GS SW ×
= Q
× V
× f
P RSNUB = C SNUB × ( V IN )
× f SW
where R DH is the high-side MOSFET driver ’ s on-resis-
tance (1 ? typical) and R GATE is the internal gate resis-
tance of the MOSFET (~2 ? ):
R GATE
R GATE + R DH
where V GS = V VDD = 5V .
In addition to the losses above, allow about 20% more for
additional losses because of MOSFET output capaci-
tances and low-side MOSFET body-diode reverse recov-
ery charge dissipated in the high-side MOSFET that is not
well defined in the MOSFET data sheet. Refer to the
MOSFET data sheet for thermal-resistance specifications
to calculate the PC board area needed to maintain the
desired maximum operating junction temperature with the
above-calculated power dissipations.
To reduce EMI caused by switching noise, add a 0.1μF
ceramic capacitor from the high-side switch drain to the
low-side switch source, or add resistors in series with
DH and DL to slow down the switching transitions.
Adding series resistors increases the power dissipation
of the MOSFET, so ensure that this does not overheat
the MOSFET.
MOSFET Snubber Circuit
Fast switching transitions cause ringing because of res-
onating circuit parasitic inductance and capacitance at
resistor (P RSNUB ) and can be calculated as:
2
where V IN is the input voltage and f SW is the switching
frequency. Choose an R SNUB power rating that meets
the specific application ’ s derating rule for the power
dissipation calculated.
Boost-Supply Diode and Capacitor
A low-current Schottky diode, such as CMSSH-3 from
Central Semiconductor, works well for most applications.
Do not use large-power diodes, because higher junction
capacitance can charge up the BST to LX voltage and
can exceed the device rating of 6V. The boost capacitor
should be 0.1μF to 4.7μF, depending on the input and
output voltages, external components, and PC board lay-
out. The boost capacitance should be as large as possi-
ble to prevent it from charging to excessive voltage, but
small enough to adequately charge during the minimum
low-side MOSFET conduction time, which happens at
maximum operating duty cycle (this occurs at minimum
input voltage). In addition, ensure that the boost capacitor
does not discharge to below the minimum gate-to-source
voltage required to keep the high-side MOSFET fully
enhanced for lowest on-resistance. This minimum gate-
to-source voltage V GS(MIN) is determined by:
the switching nodes. This high-frequency ringing
occurs at LX ’ s rising and falling transitions and can
interfere with circuit performance and generate EMI. To
V GS ( MIN ) = V VDD -
Q G
C BOOST
dampen this ringing, a series R-C snubber circuit is
added across each switch. Below is the procedure for
selecting the value of the series R-C circuit:
1) Connect a scope probe to measure V LX to GND,
and observe the ringing frequency, f R .
2) Find the capacitor value (connected from LX to
GND) that reduces the ringing frequency by half.
The circuit parasitic capacitance (C PAR ) at LX is
then equal to 1/3 the value of the added capaci-
tance above. The circuit parasitic inductance
(L PAR ) is calculated by:
where V VDD is 5V, Q G is the total gate charge of the
high-side MOSFET, and C BOOST is the boost capacitor
value.
Compensation Design
The MAX1955/MAX1956 use a voltage-mode control
scheme that regulates the output voltage by comparing
the error amplifier output (COMP) with a fixed internal
ramp to produce the required duty cycle. The inductor
and output capacitor create a double pole at the reso-
nant frequency, which has a gain drop of 40dB per
decade and phase shift of 180 ° . The error amplifier
18
______________________________________________________________________________________
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。