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参数资料
| 型号： | MAX1845EEI |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | Dual, High-Efficiency, Step-Down Controller with Accurate Current Limit |
| 中文描述： | DUAL SWITCHING CONTROLLER, 620 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封装： | 0.150 INCH, 0.025 INCH PITCH, MO-137AD, QSOP-28 |
| 文件页数： | 15/27页 |
| 文件大小： | 543K |
| 代理商： | MAX1845EEI |
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M
Dual, High-Efficiency, Step-Down
Controller with Accurate Current Limit
______________________________________________________________________________________
15
of multiple-output applications that use a flyback trans-
former or coupled inductor.
Current-Limit Circuit (ILIM_)
The current-limit circuit employs a unique
“
valley
”
current-
sensing algorithm. If the magnitude of the current-sense
signal at CS_ is above the current-limit threshold, the
PWM is not allowed to initiate a new cycle (Figure 5). The
actual peak current is greater than the current-limit
threshold by an amount equal to the inductor ripple cur-
rent. Therefore, the exact current-limit characteristic and
maximum load capability are a function of the sense
resistance, inductor value, and battery voltage.
There is also a negative current limit that prevents exces-
sive reverse inductor currents when V
OUT
is sinking cur-
rent. The negative current-limit threshold is set to
approximately 120% of the positive current limit and
therefore tracks the positive current limit when ILIM is
adjusted.
The current-limit threshold is adjusted with an internal
5μA current source and an external resistor at ILIM. The
current-limit threshold adjustment range is from 25mV
to 250mV. In the adjustable mode, the current-limit
threshold voltage is precisely 1/10 the voltage seen at
ILIM. The threshold defaults to 50mV when ILIM is con-
nected to V
CC
. The logic threshold for switchover to the
50mV default value is approximately V
CC
- 1V.
Carefully observe the PC board layout guidelines to
ensure that noise and DC errors do not corrupt the cur-
rent-sense signal seen by CS_ and GND. Mount or
place the IC close to the low-side MOSFET and sense
resistor with short, direct traces, making a Kelvin sense
connection to the sense resistor. In Figure 1, the
Schottky diodes (D1 and D2) provide current paths
parallel to the Q2/R
SENSE
and Q4/R
SENSE
current
paths, respectively. Accurate current sensing requires
D1/D2 to be off while Q2/Q4 conducts. Avoid large cur-
rent-sense voltages that, combined with the voltage
across Q2/Q4, would allow D1/D2 to conduct. If very
large sense voltages are used, connect D1/D2 in paral-
lel with Q2/Q4 only.
MOSFET Gate Drivers (DH_, DL_)
The DH and DL drivers are optimized for driving mod-
erate-size, high-side and larger, low-side power
MOSFETs. This is consistent with the low duty factor
seen in the notebook CPU environment, where a large
V
BATT
- V
OUT
differential exists. An adaptive dead-time
circuit monitors the DL output and prevents the high-
side FET from turning on until DL is fully off. There must
Table 3. Operating Mode Truth Table
ON1
ON2
SK P
DL1/DL2
MODE
COMMENTS
GND
GND
X
High*/High*
Shutdown
Low-power shutdown state. If overvoltage protection is
enabled, DL1 and DL2 are forced to V
DD
, ensuring
overvoltage protection, I
CC
< 1μA (typ).
V
CC
GND
V
CC
Switching/High*
Run (PWM), Low Noise,
Side 1 Only
GND
V
CC
V
CC
High*/Switching
Run (PWM), Low Noise,
Side 2 Only
V
CC
V
CC
V
CC
Switching/
Switching
Run (PWM), Low Noise,
Both Sides Active
Low-noise, fixed frequency PWM at all load conditions.
Low noise, high I
Q
.
V
CC
GND
GND
Switching/High*
Run (PWM/PFM), Skip
Mode, Side 1 Only
GND
V
CC
GND
High*/Switching
Run (PWM/PFM), Skip
Mode, Side 2 Only
V
CC
V
CC
GND
Switching/
Switching
Run ( P W M P FM S ki p
M od e, Both S d es Acti ve
Normal operation with automatic PWM/PFM switchover
for pulse skipping at light loads. Best light-load
efficiency.
V
CC
V
CC
X
High*/High*
Fault
Fault latch has been set by overvoltage protection circuit,
undervoltage protection circuit, or thermal shutdown.
Device will remain in fault mode until V
CC
power is
cycled or ON1/ON2 is toggled.
*DL_ high only if overvoltage protection enabled (see Output Overvoltage Protection section).
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1845EEI+ | 功能描述:电流型 PWM 控制器 Step-Down 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 |
| MAX1845EEI+T | 功能描述:电流型 PWM 控制器 Step-Down 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 |
| MAX1845EEI-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 |
| MAX1845EEI-TG05 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1845EEI-TG068 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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