rt9214 Richtek Technology Corporation, rt9214 Datasheet - Page 11

• Manufacturer Part Number: rt9214
• Description: 5v/12v Synchronous Buck Dc-dc Controller
• Manufacturer: Richtek Technology Corporation

OPS (Over Current Setting, VIN_POR and Shutdown)
1.OCP
Sense the low-side MOSFET’ s R
Connecting a resistor (R
sets the over-current trip point. R
set the converter over-current trip point (I
OPS pin function is similar to RC charging or discharging circuit, so the over-current trip point is very sensitive to
parasitic capacitance (ex. shut-down MOSFET) and the duty ratio.
Below Figures say those effect. And test conditions are Rocset = 15kΩ (over -current trip point = 20.6A), Low-side
MOSFET is IR3707.
DS9214-02
V
V
V
V
IN
OUT
IN
OUT
December 2004
= 5V, V
= 12V, V
= 1.5V
= 1.5V
CC
CC
= 12V
Time (2.5µs/Div)
= 12V
Time (5µs/Div)
OCSET
OCP
OCP
) from this pin to the source of the upper MOSFET and the drain of the lower MOSFET
OCSET
DS(ON)
UGATE (10V/Div)
UGATE (10V/Div)
, an internal 40µA current source, and the lower MOSFET on resistance, R
I
OCSET
to set over-current trip point.
OCSET
I
I
L
L
(10A/Div)
(10A/Div)
=
) according to the following equation:
R
DS(ON)
40uA
of
×
the
R
OCSET
lower
−
MOSFET
0.4V
V
V
V
V
IN
OUT
IN
OUT
OPS (200mV/Div)
= 5V, V
= 12V, V
= 1.5V
= 1.5V
CC
CC
= 12V
Time (2.5µs/Div)
= 12V
Time (5µs/Div)
OCP
OCP
OPS
(200mV/Div)
I
www.richtek.com
I
L
L
RT9214
UGATE
(10V/Div)
UGATE
(10V/Div)
(10A/Div)
(10A/Div)
DS(ON)
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