RT9206GS Richtek USA Inc, RT9206GS Datasheet - Page 13

• 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

V
Application Information
Synchronous Buck Converter
The RT9206 is specifically designed for synchronous buck
converter with wide input
operating frequency from 200kHz to 600kHz. To fully utilize
its advantages, peripheral components should be
appropriately selected. The following information provides
basic considerations for component selection.
Output Inductor Selection
The selection of output inductor is based on the
considerations of efficiency, output power and operating
frequency. Low inductance value has smaller size, but
results in low efficiency, large ripple current and high output
ripple voltage. Generally, an inductor that limits the ripple
current (ΔI
appropriate. Figure 1 shows the typical topology of
synchronous step-down converter and its related
waveforms.
IN
DS9206-12 April 2008
i
L
V
V
V
i
g1
S1
g2
L
S1
L
T
) between 20% and 50% of output current is
on
S2
ΔIL
Ts
T
off
i
S2
voltage from 4.75V to
+ V
L
L
-
V
V
i
L
+
OC
+
OR
-
-
r
C
C
i
V
-V
C
OUT
IN
OUT
I
-V
28V and
L
R
=I
OUT
L
OUT
I
OUT
V
OUT
+
-
According to Figure 1 the ripple current of inductor can be
calculated as follows :
Where :
Output Capacitor Selection
The selection of output capacitor depends on the output
ripple voltage requirement. Practically, the output ripple
voltage is a function of both capacitance value and the
equivalent series resistance (ESR) r
related waveforms of output capacitor.
ΔI
Δt = S
V
f
D = Duty Cycle
r
V
L = (V - V
V - V
S
C
Figure 1.The waveforms of synchronous step-down
OUT
IN
L
IN
= Switching frequency
= Equivalent series resistor of output capacitor
= Inductor current ripple
= Maximum input voltage
i
i
s1
s2
= Output Voltage
1
IN
OUT
turn on time
= L
OUT
)
ΔI
Δt
×
L
V
; Δt =
IN
V
×
converter
OUT
fs ΔI
D
fs
×
;D =
L
V
V
OUT
C
IN
. Figure 2 shows the
RT9206
www.richtek.com
(1)
13