RT9206GS Richtek USA Inc, RT9206GS Datasheet - Page 4

• 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
Operation
Introduction
The RT9206 is a combo controller, which integrates an
adjustable frequency, voltage mode synchronous step
down controller and two HV linear controllers. The
synchronous step down controller consists of an internal
precision reference, an internal oscillator, an error amplifier,
a PWM comparator, control logic and floating gate driver,
a programmable soft-start, a power good indicator, an over
voltage protection, an over temperature protection and short
circuit protection.
The output voltage of the synchronous converter is set
and controlled by the output of the error amplifier, which is
the amplified error signal from the sensed output voltage
and the voltage on non-inverting input, which is connected
with internal 0.8V reference voltage. The amplified error
signal is compared to a fixed frequency linear sawtooth
ramp and generates fixed frequency pulse of variable duty-
cycle, which drivers the two N-Channel external MOSFETs.
The timing of the synchronous converter is provide through
an internal oscillator circuit and can be programmed
between 200kHz to 600kHz via an external resistor
connected between RT pin and ground.
Soft-Start
RT9206 has a programmable soft-start to control the output
voltage rise time and limit the current surge at the start-
up. The soft-start will begin while V
threshold for correct start-up. Soft-start function operates
by an internal sourcing current to charge an external
capacitor to around the voltage of VINT. The soft-start signal,
SS pin, is the third input non-inverting input of the PWM
comparator. Before soft-start signal reach the bottom of
the sawtooth ramp, inverting input of the PWM comparator,
the soft-start current is twice of the normal soft-start current.
Once the soft-start signal reach the bottom of the ramp,
the soft-start current became normal, and start to increase
duty cycle from zero to the point the feedback loop takes
control.
www.richtek.com
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rises above POR
Power On Reset (POR)
The power on reset circuit assures that the MOSFET driver
outputs remain in the off state whenever the V
voltages lower than the POR threshold.
Over Current Protection
Whenever the over-current is occurred in soft-start or in
normal operation period, It will shut down PWM signal,
the MOSFET driver outputs remain in the off state, and
latch soft-start signal low until restart V
Over Voltage Protection
Once over-voltage protection occurred, it will turn on low
side MOSFET and latch soft-start signal low to prevent
end device form abnormal voltage stress. Restart V
supply voltage will release the protection.
Power Good Indicator
The power good indicator is an open drain output to show
whether the synchronous converter output ready or not.
The power good indicator is available after soft-start end.
Short-Circuit Protection
The short-circuit phenomenon is sensed by the drop of
output voltage, synchronous converter and two linear
controller. Once the short-circuit occurred, the drop of output
voltage lower than the under voltage threshold, 0.6V on
feedback, the PWM signal will shut down and both of the
external MOSFET will turn off and soft-start signal latch
low. Soft-start signal, SS, is also connected to two linear
controller error amplifier non-inverting input. Therefore,
whenever the drop of output of the synchronous converter
or two linear controllers lower than under voltage threshold,
all MOSFET drivers will turn off.
DS9206-12 April 2008
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supply voltage.
DD
supply
DD