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参数资料
| 型号： | MAX1956ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/22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
Output voltage margining shifts the output voltage by
±4% from the nominal value to simplify system testing.
Outputs also can be powered up and down in select-
able sequences to meet core and logic supply rail
requirements.
DC-to-DC PWM Controller
The MAX1955/MAX1956 step-down DC-to-DC convert-
ers use a PWM voltage-mode control scheme. The con-
troller generates the clock signal by dividing down the
internal oscillator (or SYNC signal when using an external
clock) so that each controller ’ s switching frequency
equals 1/2 the oscillator frequency. An internal transcon-
ductance error amplifier produces an integrated error
voltage at the COMP_ pin, providing high DC accuracy.
The voltage at COMP sets the duty cycle, using a PWM
comparator and a ramp generator. At the rising edge of
the clock, Regulator 1 ’ s high-side N-channel MOSFET
turns on and remains on until either the appropriate
duty cycle or the maximum duty cycle is reached.
Regulator 2 operates out of phase, so its high-side
MOSFET turns on at the falling edge of the clock.
During the on-time of each high-side MOSFET, the
associated inductor current ramps up.
current-sense signal (measured from PGND_ to LX_) is
above the current-limit threshold, the MAX1955/
MAX1956 do not initiate a new cycle, and COMP_ is
pulled to ground. Since valley current sensing is used,
the actual peak current is greater than the current-limit
threshold by an amount equal to the inductor ripple
current (Figure 2). The exact current-limit characteristic
and maximum load capacity are a function of the low-
side MOSFET ’ s on-resistance, the current-limit thresh-
old, the inductor value, and the input voltage. This
provides a robust lossless current sense that does not
require current-sense resistors.
An added feature is the implementation of Schottky
diodes D3 and D4 (as shown in Figure 5), which
reduce output short-circuit currents.
Constant-Current Limit
The adjustable current limit accommodates MOSFETs
with a wide range of on-resistance values. The current-
limit threshold is adjusted with an external resistor con-
nected from ILIM_ to GND (R ILIM _). The adjustment
range is 75mV to 300mV, measured across the low-side
MOSFET. The value of R ILIM_ is calculated using the fol-
lowing formula:
During the second half of the switching cycle, the high-
side MOSFET turns off and the low-side N-channel
MOSFET (synchronous rectifier) turns on. The inductor
R ILIM _ =
I VALLEY
0 . 15 × 5 μ A
× R DS ( ON )
releases its stored energy as its current ramps down,
providing current to the load.
High-Side Gate-Drive
Supply (BST)
The gate-drive voltage for the high-side N-channel
switch is generated by a flying capacitor. This capacitor
between BST and LX is alternately charged from the V DD
supply and placed in parallel to the high-side MOSFET ’ s
gate and source terminal through the high-side driver.
On startup, the low-side MOSFET forces LX to ground
and charges the boost capacitors to V DD through the
Schottky diodes (D1 and D2 of Figure 5). On the second
half cycle, the controller turns on the high-side MOSFET
by closing an internal switch between BST and DH. This
provides the necessary gate-to-source voltage to turn
on the high-side MOSFET, an action that boosts the 5V
gate-drive signal above the input voltage.
Current Limit
The current-limit circuit employs a “ valley ” current-
sensing algorithm that uses the on-resistance of the
low-side MOSFET as a current-sensing element. If the
where I VALLEY is the valley current limit and R DS(ON) is
the on-resistance of the low-side MOSFET. To avoid
reaching the current limit at a lower current than
expected, use the maximum value for R DS(ON) at an
elevated junction temperature. Refer to the MOSFET
manufacturer ’ s data sheet for maximum values.
I PEAK
I LOAD
I VALLEY
TIME
Figure 2. Inductor Current Waveform
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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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