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参数资料
| 型号： | MAX1917EEE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/18页 |
| 文件大小： | 0K |
| 描述： | IC CNTRLR SYNC BUCK 16-QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 应用： | 控制器，DDR |
| 输入电压： | 4.5 V ~ 22 V |
| 输出数： | 2 |
| 输出电压： | 0.4 V ~ 5 V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-QSOP |
| 包装： | 带卷 (TR) |
Tracking, Sinking and Sourcing, Synchronous Buck
Controller for DDR Memory and Termination Supplies
Voltage Reference
The voltage at REF is nominally 2.00V. Connect a 0.22μF
ceramic bypass capacitor between REF and GND.
Overcurrent Protection
The current-limit circuit employs a unique “ valley ” cur-
rent-sensing algorithm that uses the on-state resistance
of the low-side MOSFET as a current-sensing element.
If the current-sense signal is greater than the current-
limit threshold, the PWM is not allowed to initiate a new
cycle. The actual peak current is greater than the cur-
rent-limit threshold by an amount equal to the inductor
ripple current. Therefore, the exact current-limit charac-
teristic and maximum load capability are a function of
the MOSFET on-resistance, inductor value, and input
voltage. The reward for this uncertainty is robust, loss-
less overcurrent sensing. There is also a negative cur-
rent limit that prevents excessive reverse inductor
currents when V OUT is sinking current. The negative
current-limit threshold is set to approximately 110% of
the positive current limit, and tracks the positive current
limit when ILIM is adjusted. The current-limit threshold
can be adjusted with an external resistor (R ILIM ) at ILIM.
A precision 5μA pullup current source at ILIM sets a
voltage drop on this resistor, adjusting the current-limit
threshold from <50mV to >200mV. In the adjustable
mode, the current-limit threshold voltage is precisely
1/10th the voltage seen at ILIM.
Therefore, choose R ILIM equal to 2k ? /mV of the cur-
rent-limit threshold. The threshold defaults to 100mV
when ILIM is connected to VL. The logic threshold for
switchover to the 100mV default value is approximately
V L - 1V. The adjustable current limit can accommodate
various MOSFETs. A capacitor in parallel with R ILIM can
provide a variable soft-start function.
Carefully observe the PC board layout guidelines to
ensure that noise and DC errors do not corrupt the cur-
rent-sense signals seen by LX and PGND. The IC must
be mounted close to the low-side MOSFET with short,
direct traces making a Kelvin-sense connection to the
source and drain terminals. See the PC Board Layout
section.
Voltage Positioning
The quick-PWM control architecture responds virtually
instantaneously to transient load changes and elimi-
nates the control loop delay of conventional PWM con-
trollers. As a result, a large portion of the voltage
deviation during a step load change is from the equiva-
lent series resistance (ESR) of the output capacitors.
For DDR termination applications, the maximum
allowed voltage deviation is ±40mV for any output load
transition from sourcing current to sinking current.
Passive voltage positioning adjusts the converter ’ s out-
put voltage based on its load current to optimize tran-
sient response and minimize the required output
capacitance. Voltage positioning is implemented by
connecting a 2m ? resistor as shown in Figure 1.
MOSFET Drivers
The DH and DL drivers are optimized for driving mod-
erate-size, high-side and larger, low-side power
MOSFETs and are optimized for 2.5V and 5V input volt-
ages. The drivers are sized to drive MOSFETs that can
deliver up to 25A output current. An adaptive dead-
time circuit monitors the DL output and prevents the
V IN
POK
VL
POK
V+
VL
BST
V+
BST
R BST
DDR
MAX1917
EN/HSD
REF
DH
LX
DL
R DRP
2m ?
4 x 270 μ F
V OUT
DDR
EN/HSD
REF
MAX1917
DH
LX
DL
2V
ILIM
FSEL
PGND
VTT
ILIM
FSEL
PGND
VTT
GND
VTTR
VTTR
GND
VTTR
Figure 1. Using a Resistor for Voltage Positioning
Figure 2. Increasing the On Time of the High-Side MOSFET
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相关代理商/技术参数 |
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| MAX1917EEE-TG068 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1917EVKIT | 功能描述:电源管理IC开发工具 RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
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