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参数资料
| 型号： | MAX1858AEEG |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | Dual 180∑ Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and POR |
| 中文描述： | DUAL SWITCHING CONTROLLER, 660 kHz SWITCHING FREQ-MAX, PDSO24 |
| 封装： | 0.150 INCH, 0.25 INCH PITCH, MO-137AE, QSOP-24 |
| 文件页数： | 13/22页 |
| 文件大小： | 553K |
| 代理商： | MAX1858AEEG |
M
Dual 180° Out-of-Phase Buck Controllers with
Sequencing/Prebias Startup and POR
______________________________________________________________________________________
13
The adjustable current limit accommodates MOSFETs
with a wide range of on-resistance characteristics (see
the
Design Procedure
section). The current-limit thresh-
old is adjusted with an external resistor at ILIM_ (Figure
1). The adjustment range is from 50mV to 300mV, cor-
responding to resistor values of 100k
to 600k
. In
adjustable mode, the current-limit threshold across the
low-side MOSFET is precisely 1/10th the voltage seen
at ILIM_. However, the current-limit threshold defaults
to 100mV when ILIM is tied to V
L
. The logic threshold
for switchover to this 100mV default value is approxi-
mately V
L
- 0.5V.
Adjustable foldback current limit reduces power dissi-
pation during short-circuit conditions (see the
Design
Procedure
section).
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
so that trace resistance does not add to the intended
sense resistance of the low-side MOSFET.
Undervoltage Lockout and Startup
IF V
L
drops below 4.2V, the MAX1858A/MAX1875A/
MAX1876A assume that the input supply and reference
voltages are too low to make valid decisions and activate
the undervoltage lockout (UVLO) circuitry, which latches
DL and DH low to inhibit switching.
RST
is also forced
low during UVLO. To reset the latch and be ready for the
next V
L
rise, V
L
must be pulled below 2.5V.
In addition, to ensure proper startup, the value of the
capacitor at REF to GND must meet the following con-
dition:
C
REF
> ((8.29 x 10
-4
) / V
+_SLOPE
) - (1.97 x 10
-1
/ f
S_MAX
)
where V
+_SLOPE
is the actual input-voltage rise time
’
s
slew rate.
For example, if the switching frequency is set at
600kHz nominal, which is 660kHz (max), and the input-
voltage rise time
’
s slew rate is 1.6V/mS, then C
REF
should be greater than 0.22μF. Make sure C
REF
is cho-
sen large enough to cover for worst-case capacitance
tolerances and temperature coefficient.
Enable (EN), Soft-Start, and Soft-Stop
Pull EN high to enable or low to shut down both regula-
tors. See the timing diagrams, Figures 3 and 4, for
more detail.
Output-Voltage Sequencing
After the startup circuitry enables the controller, the
MAX1858A begins the startup sequence. Regulator 1
(OUT1) powers up with soft-start enabled. Once the first
converter
’
s soft-start sequence ends, regulator 2 (OUT2)
powers up with soft-start enabled. Finally, when both con-
verters complete soft-start and both output voltages
exceed 90% of their nominal values, the reset output
(
RST
) goes high (see the
Reset Output
section). Soft-stop
is initiated by pulling EN low. Soft-stop occurs in reverse
order of soft-start, allowing last-on/first-off operation.
Reset Output (
RST
) (MAX1858A/
MAX1876A Only)
RST
is an open-drain output.
RST
pulls low when either
output falls below 90% of its nominal regulation voltage.
Once both outputs exceed 90% of their nominal regulation
voltages and both soft-start cycles are completed,
RST
goes high impedance. To obtain a logic-voltage output,
connect a pullup resistor from
RST
to the logic supply volt-
age. A 100k
resistor works well for most applications. If
unused, leave
RST
grounded or unconnected.
Clock Synchronization (SYNC, CKO)
SYNC serves two functions: SYNC selects the clock out-
put (CKO) type used to synchronize slave controllers, or it
serves as a clock input so the MAX1858A/MAX1875A/
MAX1876A can be synchronized with an external clock
signal. This allows the MAX1858A/MAX1875A/MAX1876A
to function as either a master or slave. CKO provides a
clock signal synchronized to the MAX1858A/MAX1875A/
MAX1876As
’
switching frequency, allowing either in-
phase (SYNC = GND) or 90
°
out-of-phase (SYNC = V
L
)
synchronization of additional DC-DC controllers (Figure 7).
The MAX1858A/MAX1875A/MAX1876A support the fol-
lowing three operating modes:
SYNC = GND:
The CKO output frequency equals
REG1
’
s switching frequency (f
CKO
= f
DH1
) and the
CKO signal is in phase with REG1
’
s switching fre-
quency. This provides 2-phase operation when syn-
chronized with a second slave controller.
SYNC = V
L
:
The CKO output frequency equals two
times REG1
’
s switching frequency (f
CKO
= 2f
DH1
)
and the CKO signal is phase shifted by 90
°
with
respect to REG1
’
s switching frequency. This pro-
vides 4-phase operation when synchronized with a
second MAX1858A/MAX1875A/MAX1876A (slave
controller).
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1858AEEG+ | 功能描述:电压模式 PWM 控制器 Dual 180 Out Buck Controllers RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX1858AEEG+T | 功能描述:电压模式 PWM 控制器 Dual 180 Out Buck Controllers RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX1858AEEG-T | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1858EEG | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1858EEG+ | 功能描述:电压模式 PWM 控制器 Dual 180 Out Buck Controllers RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
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