参数资料
型号: MAX1845ETX+T
厂商: Maxim Integrated Products
文件页数: 13/27页
文件大小: 0K
描述: IC REG CTRLR BUCK PWM CM 36-TQFN
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 2,500
PWM 型: 电流模式
输出数: 2
频率 - 最大: 540kHz
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: -40°C ~ 85°C
封装/外壳: 36-WFQFN 裸露焊盘
包装: 带卷 (TR)
Dual, High-Efficiency, Step-Down
Controller with Accurate Current Limit
V+
2V TO 28V
V DD
5V INPUT
V DD
I LIM1
V+
I LIM2
V DD
PGND*
V CC - 1V
0.5V
V CC - 1V
0.5V
V DD
V+
BST1
BST2
V+
DH1
MAX1845
DH2
LX1
PWM
CONTROLLER
PWM
CONTROLLER
LX2
CS1
V DD
DL1
OUT1
FB1
UVP
OVP
TON
SKIP
PGOOD
(FIGURE 3)
(FIGURE 3)
CS2
V DD
DL2
OUT 2
FB2
V CC
2V
REF
REF
20 Ω
V DD
AGND*
FAULT1
ON1
ON2
FAULT2
* IN THE MAX1845EEI, AGND AND PGND ARE INTERNALLY CONNECTED AND CALLED GND.
Figure 2. Functional Diagram
where K is the on-time scale factor (Table 4). The load-
current level at which PFM/PWM crossover occurs,
I LOAD(SKIP) , is equal to 1/2 the peak-to-peak ripple cur-
rent, which is a function of the inductor value (Figure
4). For example, in the standard application circuit with
V OUT1 = 2.5V, V IN = 15V, and K = 2.96μs (Table 4),
switchover to pulse-skipping operation occurs at I LOAD
= 0.7A or about 1/6 full load. The crossover point
occurs at an even lower value if a swinging (soft-satu-
ration) inductor is used.
The switching waveforms may appear noisy and asyn-
chronous when light loading causes pulse-skipping
operation, but this is a normal operating condition that
results in high light-load efficiency. Trade-offs in PFM
noise vs. light-load efficiency are made by varying the
inductor value. Generally, low inductor values produce
a broader efficiency vs. load curve, while higher values
result in higher full-load efficiency (assuming that the
coil resistance remains fixed) and less output voltage
ripple. Penalties for using higher inductor values
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