IR3843AMTR1PBF International Rectifier, IR3843AMTR1PBF Datasheet - Page 17

• Manufacturer Part Number: IR3843AMTR1PBF
• Description: IC REG SYNC BUCK 3A 15-QFN
• Manufacturer: International Rectifier
• Series: SupIRBuck™r
• Type: Step-Down (Buck)r

Specifications of IR3843AMTR1PBF

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.7 ~ 18.9 V
• Current - Output: 3A
• Frequency - Switching: 225kHz ~ 1.32MHz
• Voltage - Input: 1.5 ~ 21 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 15-PowerVQFN
• Power - Output: 682mW
• Part Status: Active
• Package: PQFN / 5 x 6
• Circuit: Single Output
• Iout (a): 3
• Switch Freq (khz): 250 - 1200
• Input Range (v): 1.5 - 21
• Output Range (v): 0.7 - 0.9*Vin
• Ocp Otp Uvlo Pre-bias Soft Start And: PGOOD + EN + SEQ
• Digital Home Media: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: IR3843AMTR1PBFTR

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 IR3843A, the typical
minimum on-time is specified as 100 ns.
Any design or application using the IR3843A
must ensure operation with a pulse width that is
higher than this minimum on-time and preferably
higher than 150 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.
In any application that uses the IR3843A, the
following condition must be satisfied:
The minimum output voltage is limited by the
reference voltage and hence V
Therefore, for V
Therefore, even at the minimum switching
frequency 250 kHz, no input voltage higher than
18.5V may be reliably converted down to 0.7V
without excessive jitter or pulse skipping over the
complete load range.
In general, practical considerations dictate that
any application that demands a pulse width
smaller than 175ns may not exhibit jitter free
operation over the entire load range.
Rev 13.0
∴
∴
V
in
V
∴
∴
t
in
×
on
V
t
on
F
×
t
(min)
in
on
s
(min)
F
×
out(min)
s
=
≤
=
F
≤
≤
V
s
V
F
D
≤
t
in
t
out
150
s
V
on
≤
0.7
on
V
out
×
(min)
= 0.7 V,
(min)
t
in
V
on
V
F
ns
V
out
×
out
(min)
s
F
=
s
4
.
67
out(min)
×
10
6
V/s
= 0.7 V.
Maximum Duty Ratio Considerations
A fixed off-time of 200 ns maximum is specified
for the IR3843A. 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 IR3843A can operate. To allow a
margin of 50ns, the maximum operating duty
ratio in any application using the IR3843A should
still accommodate about 250 ns off-time. Fig 10.
shows a plot of the maximum duty ratio v/s the
switching frequency, with 250 ns off-time.
95
90
85
80
75
70
300
Fig. 10. Maximum duty cycle v/s switching
400
frequency.
500
600
Switching Frequency (kHz)
IR3843AMPbF
700
800
900
1000
PD-97509
1100
17
1200