R1223N152A RICOH [RICOH electronics devices division], R1223N152A Datasheet - Page 7

• Manufacturer Part Number: R1223N152A
• Description: PWM/VFM Step-down DC/DC Converter
• Manufacturer: RICOH [RICOH electronics devices division]

n n n n TYPICAL APPLICATIONS AND APPLICATION HINTS
l As shown in the block diagram, a parasitic diode is formed in each terminal, each of these diodes is not formed
l The operation of Latch-type protection circuit is as follows;
l The operation of Reset-type protection circuit is as follows;
l Set external components as close as possible to the IC and minimize the connection between the components
l Use capacitors with a capacity of 22mF or more for V
l Choose an inductor that has sufficiently small D.C. resistance and large allowable current and is hard to reach
Rev. 1.11
CE CONTROL
and the IC. In particular, a capacitor should be connected to V
as tantalum capacitors. We recommend you to use capacitors with an allowable voltage which is at least twice as
When you use these ICs, consider the following issues;
for load current, therefore do not use it in such a way. When you control the CE pin by another power supply,
do not make its "H" level more than the voltage level of V
When the maximum duty cycle continues longer than the delay time for protection circuit, (Refer to the Electrical
Characteristics) the protection circuit works to shut-down Power MOSFET with its latching operation. Therefore
when an input/output voltage difference is small, the protection circuit may work with small load current.
IC with power-on. However, in the case of restarting this IC with power-on, after the power supply is turned off, if a
certain amount of charge remains in C
even after power-on.
voltage of DC/DC converter is longer than soft-starting time plus delay time for protection circuit, protection circuit
works before V
voltage is not ready, make this IC be standby mode(CE=”L”), and when the power supply is ready (the voltage level
of V
When the maximum duty cycle continues longer than the delay time for protection circuit, (Refer to the Electrical
Characteristics) the protection circuit works to restart with soft-start operation. Therefore when an input/output
voltage difference is small, the protection circuit may work with small load current.
sufficient grounding and reinforce supplying. A large switching current flows through the connection of power
supply, an inductor and the connection of V
voltage level of power supply of the IC fluctuates with the switching current. This may cause unstable operation of
the IC.
much as setting output voltage. This is because there may be a case where a spike-shaped high voltage is
generated by an inductor when an external transistor is on and off.
magnetic saturation. And if the value of inductance of an inductor is extremely small, the I
absolute maximum rating at the maximum loading.
To release the protection latch state, after disable this IC with a chip enable circuit, enable it again, or restart this
If rising transition speed of supply voltage is too slow, or the time which is required for V
PMOS : HAT1020R(Hitachi), Si3443DV(Siliconix)
SD1 : RB491D (Rohm)
C
IN
IN
is equal or more than the voltage level of V
C
: 10mF52(Tantalum Type)
IN
IN
voltage reaches Output voltage of DC/DC converter. To prevent this action, while power supply
V
CE
IN
PMOS
GND
EXT
IN,
V
OUT
or some voltage is forced to V
OUT.
If the impedance of the connection of power supply is high, the
- 7 -
OUT
SD1
OUT
), make it enable(CE=”H”).
C
L
OUT
L
IN
pin, and with good high frequency characteristics such
: 47mF(Tantalum Type)
pin.
: CD105(Sumida, 27mH)
OUT
C
OUT
pin with the minimum connection. And make
IN
from C
Load
IN,
this IC might not be restarted
IN
LX
voltage to reach Output
may exceed the
12345