R1211D002A RICOH electronics devices division, R1211D002A Datasheet - Page 13

• Manufacturer Part Number: R1211D002A
• Description: Step-up DC/DC Controller
• Manufacturer: RICOH electronics devices division

When the voltage level of SS becomes the setting voltage with the ration of R1 and R2 or more, switching operation
starts. V
cycle depends on the lowest level among AMPOUT, SS, and DTC of the 4 input terminals in the PWM comparator.
(Step3)
When SS reaches 1V, soft-start operation finishes. V
operation becomes normal mode.
<Latch Protection Operation>
The operation of Latch protection circuit is as follows: When AMPOUT becomes “H” and the IC detects maximum
duty cycle, charge to an external capacitor, C2 of DELAY pin starts. And maximum duty cycle continues and the
voltage of DELAY pin reaches delay voltage detector threshold, V
external power MOSFET.
R1211X002B/D version. Otherwise, make supply voltage down to UVLO detector threshold or lower, and make it rise
up to the normal input voltage.
During the soft-start time, if the duty cycle may be the maximum, protection circuit does not work and DELAY pin is
fixed at GND level.
The delay time of latch protection can be calculated with C2, V
next formula.
Once after the maximum duty is detected and released before delay time, charge to the capacitor is halt and delay
pin outputs “L”.
Rev. 1.10
To release the latch protection operation, make the IC be standby mode with CE pin and make it active in terms of
t=C2 V
EXT
REF
DLY
SS,VREF
/I
level gradually increases together with SS level. V
Step1
DLY1
AMPOUT
Normal
V
FB
Output Short
AMPOUT
maxduty
DELAY
V
V
OUT
IN
- 13 -
Operation
REF
becomes constant voltage (=1V). Then the switching
Step2
OUT
DLY
, and Delay Pin Charge Current, I
is also rising with balancing V
DLY
, outputs “L” to EXT pin and turns off the
Latched
V
DLY
DTC
DTC
AMPOUT
AMPOUT
SS
V
FB
,VREF
REF
DLY1
and V
, as in the
FB
. Duty