RT9218GS Richtek USA Inc, RT9218GS Datasheet - Page 12

• Manufacturer Part Number: RT9218GS
• Description: IC CTRLR PWM SYNC BUCK 14SOP
• Manufacturer: Richtek USA Inc

Specifications of RT9218GS

• Topology: Step-Down (Buck) Synchronous (1), Linear (LDO) (1)
• Function: Any Function
• Number Of Outputs: 2
• Frequency - Switching: 300kHz
• Voltage/current - Output 1: Controller
• Voltage/current - Output 2: Controller
• W/led Driver: No
• W/supervisor: No
• W/sequencer: No
• Voltage - Supply: 5V, 12V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 14-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

RT9218
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.
www.richtek.com
12
V
V
V
V
IN
OUT
IN
OUT
= 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
to set over-current trip point.
OCSET
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
DS9218-08 March 2007
OPS
(200mV/Div)
I
I
L
L
UGATE
(10V/Div)
UGATE
(10V/Div)
(10A/Div)
(10A/Div)
DS(ON)
,