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| 型号： | MAX1956ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 15/22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
V RIPPLE ( ESL ) = V IN ?
? ESL + L ?
I P - P = IN OUT × OUT
P LSCC = ? 1 - OUT ? × ( I LOAD ) × R DS ( ON )
The output voltage ripple due to the ESL of the output
capacitor is:
? ESL ?
?
I P-P is the peak-to-peak inductor current:
V - V V
f SW × L V IN
These equations are suitable for initial capacitor selec-
tion to meet the ripple requirement, but final values can
depend on the relationship between the LC double-pole
frequency and the capacitor ESR zero. Generally, the
ESR zero is higher than the LC double pole. However, it
is preferable to keep the ESR zero as close to the LC
double pole as possible to negate the sharp phase shift
of the typically high-Q double-LC pole (see the
Compensation Design section). Solid polymer electrolytic
capacitors are recommended because of their low ESR
and ESL at the switching frequency. Higher output-cur-
rent applications require multiple output capacitors con-
nected in parallel to meet the output ripple voltage
requirements.
The response to a load transient depends on the output
capacitor. After a load transient, the output voltage
instantly changes by ESR x ? I LOAD + ESL x dI/dt. Before
the controller can respond, the output deviates further,
depending on the inductor and output capacitor values.
After a short time (see the Typical Operating
Characteristics ), the controller responds by regulating
the output voltage back to its nominal state. The
response time depends on the closed-loop bandwidth.
With a higher bandwidth, the response is faster, thus
preventing the output voltage from deviating further from
its nominal value. Do not exceed the capacitor ’ s voltage
loss equal to switching loss at nominal input voltage
and maximum output current (see below). For low-side
MOSFET, make sure that it does not spuriously turn on
because of dV/dt caused by high-side MOSFET turning
on, as this would result in shoot-through current
degrading the efficiency. MOSFETs with a lower Q GD -
to-Q GS ratio have higher immunity to dV/dt.
For proper thermal-management design, calculate the
power dissipation at the desired maximum operating
junction temperature, maximum output current, and
worst-case input voltage (for low-side MOSFET, worst
case is at VIN(MAX); for high-side MOSFET, it could be
either at VIN(MIN) or VIN(MAX)). High-side MOSFET
and low-side MOSFET have different loss components
due to the circuit operation. Low-side MOSFET oper-
ates as a zero voltage switch; therefore, major losses
are: the channel conduction loss (P LSCC ), the body-
diode conduction loss (P LSDC ), and the gate-drive loss
(P LSDR ):
? V ? 2
? V IN ?
Use R DS(ON) at T J(MAX) :
P LSDC = 2 I LOAD × V F × t DT × f SW
where V F is the body-diode forward-voltage drop, t DT is
the dead time (~25ns), and f SW is the switching fre-
quency.
Because of the zero-voltage switch operation, low-side
MOSFET gate-drive loss occurs as a result of charging
and discharging the input capacitance, (C ISS ). This
loss is distributed among the average DL gate driver ’ s
pullup and pulldown resistance, (R DL (0.68 ? typ)), and
the internal gate resistance (R GATE ) of the MOSFET
(~2 ? ). The drive power dissipated is given by:
P LSDR = C ISS × ( V GS ) × f SW ×
or ripple-current ratings.
MOSFET Selection
2
R GATE
R GATE + R DL
P HSCC = × ( I LOAD ) × R DS ( )
V IN
The MAX1955/MAX1956 drive external, logic-level, N-
channel MOSFETs as the circuit-switch elements. The
key selection parameters:
On-resistance (R DS(ON) ): the lower the better.
Maximum drain-to-source voltage (V DSS ): should be
at least 20% higher than input supply rail at the high-
side MOSFET ’ s drain.
Gate charges (Q G , Q GD , Q GS ): the lower the better.
Choose the MOSFETs with rated R DS(ON) at V GS =
4.5V. For a good compromise between efficiency and
cost, choose the high-side MOSFET that has a conduction
High-side MOSFET operates as a duty-cycle control
switch and has the following major losses: the channel
conduction loss (P HSCC ), the VI overlapping switching
loss (P HSSW ), and the drive loss (P HSDR ). High-side
MOSFET does not have body-diode conduction loss
because the diode never conducts current:
V OUT 2
ON
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相关代理商/技术参数 |
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|---|---|
| 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 |
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