sip12202 Vishay, sip12202 Datasheet - Page 4

• Manufacturer Part Number: sip12202
• Description: Synchronous Step Down Controller
• Manufacturer: Vishay

SiP12202
Vishay Siliconix
FUNCTIONAL BLOCK DIAGRAM
DETAILED OPERATIONAL DESCRIPTION
Enable/ON State:
The COMP/SD pin has 10 µA pull up current to ensure
auto startup as soon as the pin is released by the
external pull down MOS. When the internal reference
is ready, there will be a clamp current applied at
COMPSD; this is to ensure the COMPSD pin will not
go below 600 mV inadvertently due to the amplifier
excursion or noise. The COMPSD has to go above 600
mV to enable the chip fully.
Disable/Shutdown/Off State
To disable the chip, the COMP/SD pin has to pulled
below 150 mV typically and the external pull down
MOSFET has to be able to sink at least 250 µA. Once
the pin reaches a voltage below the 150 mV level, the
chip will go into shutdown mode with only essential
curcuitry alive and the current bias of the chip will be
cut down to 30 µA level typically. Both High Side and
Low Side Gates are off.
UVLO:
The chip enters into Under Voltage Lockout when V
is below 2.3 V (typical). Both High Side Gate and Low
Side Gate will be turned off. The chip will go out of
UVLO mode when V
Soft Start:
Once the chip is out of shutdown and UVLO mode the
soft start is initiated. The soft start is done accom-
www.vishay.com
4
Vin
FB
IN
is above 2.4 V (typical).
0.6 V
Soft Start
UVLO
GM
SD/Comp
Shut Down
PWM Comp
0.45 V
500KHz
OSC
Over Temp
FB
New Product
ΔVosc
Agnd
IN
Over Voltage
SiP12202
Gate Control
BBM
Logic
plished by ramping up the internal reference. During
soft start mode the chip can not enter into fault mode.
If there is an over current condition (current limit condi-
tion), the High Side Gate will be turned off and the Low
Side will be turned on. Once the soft start timing
elapses, the chip enters into a normal state of opera-
tion.
Output Over Voltage State:
When the Output voltage goes above 1.083 times
nominal Output Voltage, the over voltage circuit will act
as a high speed clamp and the High Side Gate will be
turned off and the Low Side Gate will be on. The con-
dition will persist until the Output voltage drops below
the trigger voltage minus a hysteresis.
Output Over Current State:
The SiP12202 will enter a cycle by cycle over current
condition when the voltage on the LX pin falls below
V
High Side MOSFET is turned off for the duration of the
existing cycle. At the beginning of the next cycle the
High Side MOSFET turns on and the LX voltage is
measured again. If the over current condition still
exists, the High Side MOSFET is turned off again. This
is repeated seven consecutive times after which the IC
will go into a fault state. If the over current condition is
removed before seven consecutive cycles the IC
reverts to normal operating mode.
IN
by 300 mV. During the over current condition the
Over Current
Sense
Comp
Vin
PG
Vin
DH
LX
DL
Pgnd
S-52332–Rev. B, 07-Nov-05
Document Number: 73542