RT9206GS Richtek USA Inc, RT9206GS Datasheet - Page 20

• Manufacturer Part Number: RT9206GS
• Description: IC CTRLR DUAL SYNC BUCK 16SOP
• Manufacturer: Richtek USA Inc

Specifications of RT9206GS

• Topology: Step-Down (Buck) Synchronous (1), Linear (LDO) (2)
• Function: Any Function
• Number Of Outputs: 3
• Frequency - Switching: 200kHz ~ 600kHz
• Voltage/current - Output 1: Controller
• Voltage/current - Output 2: Controller
• Voltage/current - Output 3: Controller
• W/led Driver: No
• W/supervisor: No
• W/sequencer: No
• Voltage - Supply: 4.75 V ~ 28 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

RT9206
Linear Regulator
Output Capacitor Selection
Solid tantalum capacitors are recommended for use on
the output capacitors of LDO because their typical ESR is
very close to the ideal value required for loop compensation.
Tantalums also have good temperature stability: a good
quality tantalum will typically show a capacitance value
that varies less than 10-15% across the full temperature
range of 125 C to 40 C. ESR will vary only about 2X going
from the high to low temperature limits.
Linear Regular MOSFETs Selection
The main consideration of pass MOSFETs of linear regulator
is package selection for efficient removal of heat. The power
dissipation of a linear regulator is
The criterion for selection of package is the junction
temperature below the maximum desired temperature with
the maximum expected ambient temperature.
Layout Consideration
Layout is very important in high frequency switching
converter design. If designed improperly, the PCB could
radiate excessive noise and contribute to the converter
instability. First, place the PWM power stage components.
Mount all the power components and connections in the
top layer with wide copper areas. The MOSFETs of Buck,
inductor, and output capacitor should be as close to each
other as possible. This can reduce the radiation of EMI
due to the high frequency current loop. If the output
capacitors are placed in parallel to reduce the ESR of
capacitor, equal sharing ripple current should be
considered. Place the input capacitor directly to the drain
of high-side MOSFET. The MOSFETs of linear regulator
should have wide pad to dissipate the heat. In multilayer
PCB, use one layer as power ground and have a separate
control signal ground as the reference of the all signal. To
avoid the signal ground is effect by noise and have best
load regulation, it should be connected to the ground
terminal of output. Furthermore, follows below guidelines
can get better performance of IC :
www.richtek.com
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Plinear = (V - V
IN
OUT
) I
OUT
(W)
(26)
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The IC needs a bypassing ceramic capacitor C1 as a
R-C filter to isolate the pulse current from power stage
and supply to IC, so the ceramic capacitor C1 should
be placed adjacent to the IC.
Place the high frequency ceramic decoupling close
to the power MOSFETs.
The feedback part should be placed as close to IC as
possible and keep away from the inductor and all noise
sources.
The components of bootstraps (C8, C9 and D1) should
be closed to each other and close to MOSFETs.
The PCB trace from UGATE and LGATE of controller
to MOSFETs should be as short as possible and can
carry 1A peak current.
Place all of the components as close to IC as possible.
Figure 11 shows the typical PCB layout of synchronous
Buck converter with RT9206 controller
Figure 11. The PCB layout of synchronous Buck
converter with RT9206 controller
DS9206-12 April 2008