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MAX8969 参数 Datasheet PDF下载

MAX8969图片预览
型号: MAX8969
PDF下载: 下载PDF文件 查看货源
内容描述: 升压转换器为手持式应用 [Step-Up Converter for Handheld Applications]
分类和应用: 转换器升压转换器
文件页数/大小: 18 页 / 1996 K
品牌: MAXIM [ MAXIM INTEGRATED PRODUCTS ]
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Step-Up Converter  
for Handheld Applications  
OUT_  
C
OUT  
22µF  
MAX8969  
IN  
REFERENCE  
C
IN  
4.7µF  
RAMP  
IN  
GENERATOR  
ATM  
COMPARATOR  
IN  
P1  
N1  
TRUE  
SHUTDOWN  
ATM  
TRACK  
PWM  
LOGIC  
0.95 x  
OUT_TARGET  
V
CONTROL  
LOGIC  
ENABLE  
TREN  
EN  
CURRENT  
LIMIT  
GND_  
LX_  
L1  
1µH  
Figure 1. Functional Diagram  
During this period, as well as being limited by the volt-  
age, ramp rate current is limited by the normal 2.6A boost  
mode current limit.  
Detailed Description  
The MAX8969 is a step-up DC-DC switching converter  
that utilizes a fixed-frequency PWM architecture with  
True Shutdown. With an advanced voltage-positioning  
control scheme and high 3MHz switching frequency, the  
IC is inexpensive to implement and compact, using only  
a few small easily obtained external components. Under  
light-load conditions, the IC switches only when needed,  
consuming only 45FA (typ) of quiescent current. The IC  
is highly efficient with an internal switch and synchronous  
rectifier. Shutdown typically reduces the quiescent current  
to 1FA (typ). Low quiescent current and high efficiency  
make this device ideal for powering portable equipment.  
In boost mode, the step-up converter boosts to  
V
from battery input voltages ranging from  
OUT_TARGET  
2.5V to V . When the input voltage ranges  
OUT_TARGET  
from 0.95 x V  
to 5.5V, the IC enters ATM and  
OUT_TARGET  
the output voltage approximately follows the input volt-  
age. During boost mode, the input current limit is set to  
2.6A to guarantee delivery of the rated out current (e.g.,  
1A output current when boosting from a 2.5V input supply  
to a 3.7V output).  
Control Scheme  
The step-up converter uses a load/line control scheme.  
The load/line control scheme allows the output voltage  
to sag under load, but prevents overshoot when the  
load is suddenly removed. The load/line control scheme  
reduces the total range of voltages reached during  
transients at the expense of DC output impedance.  
Internal soft-start limits inrush current to less than 720mA  
(typ), while output voltage is less than input voltage. Once  
output voltage approaches input voltage approaches  
input voltage after a brief delay, output voltage is boosted  
to its final value at a rate of approximately 25mV/µs.  
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