rt9202 ETC-unknow, rt9202 Datasheet - Page 10

• Manufacturer Part Number: rt9202
• Description: Single Synchronous Buck Dc-dc Controller
• Manufacturer: ETC-unknow

RT9202
comparator trips to set the over-current latch. Both
V
capacitor across R
variations of V
current function will be tripped at a peak inductor
current (I
The OC trip point varies with MOSFET’s R
temperature variations. The temperature coefficient
of I
R
tripping in the normal operating load range,
determine the R
above with:
1. The maximum R
2. The minimum I
3. Determine I
where ∆I is the output inductor ripple current.
Under Voltage and Over Voltage Protection
The voltage at FB pin is monitored and protected
against OC (over current), UV (under voltage), and
OV (over voltage). The UV threshold is 0.5V and OV-
threshold is 1.0V. Both UV/OV detection have 30µS
triggered delay. When OC or UV trigged, a hiccup re-
start sequence will be initialized, as shown in Fig.4.
Only 3 times of trigger are allowed to latch off. Hiccup
is disabled during soft-start interval.
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10
SET
DS(ON)
temperature
OCSET
and V
OC
OVER-CURRENT TRIP:
V
iD
DS
temperature variations. To avoid over-current
PWM
×R
PEAK
> V
is 2500ppm that is used to compensate
_
DS(ON)
SET
DS
) determined by:
CONTROL
IN
PEAK
> I
are referenced to V
GATE
OCSET
due to MOSFET switching. The over-
OCSET
OCSET
for I
DRIVE
I
40µA
OCSET
OCSET
OCSET
SD(ON)
resistor value from the equation
PEAK
× R
from the characteristics
Fig.3
OCSET
helps V
> I
VCC
at the highest junction
UGATE
OUT(MAX)
PHASE
V
V
R
PHASE
OCSET
V
OCSET
SET+
OCSET
= V
= V
IN
+ (∆I)/2
IN
IN
V
V
and a small
i
IN
DS+
D
- V
- V
tracking the
= +5V
DS
SET
DS(ON)
Shutdown
Pulling low the OCSET pin by a small single
transistor can shutdown the RT9202 PWM controller
as shown in typical application circuit.
0A
4V
2V
0V
COUNT = 1 COUNT = 2
T0T1
OVERLOAD
APPLIED
T2
Fig. 4
TIME
DS9202-02 August 2002
COUNT = 3
T3