参数资料
型号: MAX1897ETP+T
厂商: Maxim Integrated Products
文件页数: 12/33页
文件大小: 0K
描述: IC REG CTRLR BUCK PWM 20-TQFN
标准包装: 2,500
系列: Quick-PWM™
PWM 型: 控制器
输出数: 1
频率 - 最大: 550kHz
电源电压: 4.5 V ~ 5.5 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: 0°C ~ 85°C
封装/外壳: 20-WQFN 裸露焊盘
包装: 带卷 (TR)
Quick-PWM Slave Controllers for
Multiphase, Step-Down Supplies
Table 2. Component Suppliers
MANUFACTURER
MOSFETS
Fairchild Semiconductor
International Rectifier
Siliconix
CAPACITORS
Kemet
Panasonic
Sanyo
Taiyo Yuden
INDUCTORS
Coilcraft
Coiltronics
Sumida
PHONE
[COUNTRY CODE]
[1] 888-522-5372
[1] 310-322-3331
[1] 203-268-6261
[1] 408-986-0424
[1] 847-468-5624
[65] 281-3226 (Singapore)
[1] 408-749-9714
[03] 3667-3408 (Japan)
[1] 408-573-4150
[1] 800-322-2645
[1] 561-752-5000
[1] 408-982-9660
WEBSITE
www.fairchildsemi.com
www.irf.com
www.vishay.com
www.kemet.com
www.panasonic.com
www.secc.co.jp
www.t-yuden.com
www.coilcraft.com
www.coiltronics.com
www.sumida.com
t ON = K ? COMP ?
= K ? OUT ? + K ? COMP C ?
transition on the TRIG input, the slave controller ’ s
inductor current is below its current-limit threshold, and
the minimum off time has expired. For the MAX1887, a
rising edge on the trigger input (TRIG) initiates a new
cycle. For the MAX1897, the trigger input ’ s polarity is
selected by connecting POL to V CC (rising edge) or to
GND (falling edge).
At the slave controller ’ s core is the one-shot that sets
the high-side switch ’ s on-time. This fast, low-jitter one-
shot adjusts the on-time in response to the input volt-
age and the difference between the inductor currents in
the master and the slave. Two identical transconduc-
tance amplifiers (G MM = G MS ) integrate the difference
between the master and slave current-sense signals.
The summed output is connected to COMP, allowing
adjustment of the integration time constant with a com-
pensation capacitor connected at COMP. The resulting
compensation current and voltage may be determined
by the following equations:
I COMP = G MM ( V CM + ? V CM ? ) ? G MS ( V CS + ? V CS ? )
V COMP = V OUT + I COMP Z COMP
where Z COMP is the impedance at the COMP output.
The PWM controller uses this integrated signal (V COMP )
to set the slave controller ’ s on time. When the master
and slave current-sense signals (CM+ to CM- and CS+
to CS-) become unbalanced, the transconductance
amplifiers adjust the slave controller ’ s on time, allowing
the slave inductor current to increase or decrease until
the current-sense signals are properly balanced.
? V ?
? V IN ?
? V ? ? I Z ?
? V IN ? ? V IN ?
= (Master ’ s on time) + (Slave ’ s on-time
correction due to current imbalance)
This control algorithm results in balanced inductor cur-
rents with the slave switching frequency synchronized
to the master. Since the master operates at nearly con-
stant frequency, the slave will as well. The benefits of a
constant switching frequency are twofold: first, the fre-
quency can be selected to avoid noise-sensitive
regions of the spectrum; second, the inductor ripple-
current operating point remains relatively constant,
resulting in easy design methodology and predictable
output voltage ripple.
Multiple phase switching effectively distributes the load
among the external components, thereby improving the
overall efficiency. Distributing the load current between
multiple phases lowers the peak inductor current by the
12
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