R1212D002A RICOH [RICOH electronics devices division], R1212D002A Datasheet - Page 14

• Manufacturer Part Number: R1212D002A
• Description: STEP-UP DC/DC CONTOLLER
• Manufacturer: RICOH [RICOH electronics devices division]

14
TIMING CHART
<Soft-start Operation>
operation.
rising (over-shoot) and inrush current.
starts. Following with the increase of the voltage level of V
the DTC voltage is also rising, then, soft-start operation starts. When the DTC voltage crosses the chopping
wave level inside the IC, EXT pin starts switching, then, step-up operation begins. During this term, the output
voltage does not reach the set output voltage. Therefore the output of the amplifier is "H". Besides, the protection
circuit may work and the IC charges the DELAY pin. Because of this, the soft-start time should be set shorter
than the latch protection delay time.
the normal state. In other words, the level is determined with the input voltage, the output voltage, and the output
current. When the level of AMPOUT becomes falling, charging the DELAY pin stops and discharges to the GND.
The soft-start time (the time for the DTC pin voltage becoming to V
formula.
R1212D
The timing chart below describes the state of each pin from the power-on until the IC entering the stable
By raising the voltage of the DTC pin slowly, the switching duty cycle is limited, and prevent the drastic voltage
When the V
After the initial stage, when the output voltage reaches the set output voltage, the level of AMPOUT becomes
T≅1/α×ln(V
DTC
IN
voltage becomes equal or more than the UVLO released voltage (V
×α/β+1), herein, α=−1/C
(V
UVLO
+V
V
HYS
REFOUT
DTC
)
OSC
7
Soft-start Time
×(1/R
R
R
5
6
5
+1/R
C
7
6
), and β=V
REFOUT
REFOUT
, the internal oscillator begins to operate, then
/(C
DTC
7
×R
level) can be estimated with the next
5
).
UVLO
+V
HYS
), V
REFOUT
V
V
DTC
A
D
EXT
IN
REFOUT
MPOUT
ELAY
operation