参数资料
型号: IRDC3831
厂商: International Rectifier
文件页数: 15/31页
文件大小: 0K
描述: BOARD EVAL SYNC BUCK CONVERTER
产品变化通告: (EP) Parts Discontinuation 25/May/2012
标准包装: 1
系列: SupIRBuck™
主要目的: DC/DC,步降
输出及类型: 1,非隔离
输出电压: 0.75V
电流 - 输出: 8A
输入电压: 12V
稳压器拓扑结构: 降压
频率 - 开关: 400kHz
板类型: 完全填充
已供物品:
已用 IC / 零件: IR3831
IR3831MPbF
Minimum on time Considerations
The minimum ON time is the shortest amount of
time for which the Control FET may be reliably
turned on, and this depends on the internal
timing delays. For the IR3831, the typical
minimum on-time is specified as 50 ns.
Any design or application using the IR3831 must
ensure operation with a pulse width that is higher
than this minimum on-time and preferably higher
than 100 ns. This is necessary for the circuit to
operate without jitter and pulse-skipping, which
can cause high inductor current ripple and high
output voltage ripple.
Maximum Duty Ratio Considerations
A fixed off-time of 200 ns maximum is specified
for the IR3831. This provides an upper limit on
the operating duty ratio at any given switching
frequency. It is clear, that higher the switching
frequency, the lower is the maximum duty ratio at
which the IR3831 can operate. To allow some
margin, the maximum operating duty ratio in any
application using the IR3831 should still
accommodate about 250 ns off-time. Fig 9.
shows a plot of the maximum duty ratio v/s the
switching frequency, with 250 ns off-time.
t on =
=
D
F s
V out
V in × F s
95
90
85
80
75
M a x Duty Cycle
In any application that uses the IR3831, the
following condition must be satisfied:
t on (min) ≤ t on
70
65
60
55
250
450
650
850
1050
1250
1450
1650
∴ t on (min) ≤
∴ V in × F s ≤
V out
V in × F s
V out
t on (min)
The minimum output voltage for the IR3831 is
limited to V out(min) = 0.6 V.
S w itching Frequency (kH z )
Fig. 9. Maximum duty cycle v/s switching
frequency.
∴ V in × F s ≤
V out (min)
t on (min)
∴ V in × F s ≤
0.6 V
100 ns
= 6 × 10 6 V/s
Furthermore, for the IR3831, especially for active
bus termination applications, it is strongly
recommended to use a switching frequency of
400 kHz to obtain clean and jitter free operation
in sourcing as well as sinking modes. Therefore,
the maximum input voltage that may be stepped
down to 0.6V at 400 kHz without jitter or pulse
skipping is 15 V.
11/05/10
15
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