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RT8206B Schematic ( PDF Datasheet ) - Richtek

Teilenummer RT8206B
Beschreibung (RT8206A/B) Main Power Supply Controllers
Hersteller Richtek
Logo Richtek Logo 




Gesamt 26 Seiten
RT8206B Datasheet, Funktion
RT8206A/B
High-Efficiency, Main Power Supply Controllers
for Notebook Computers
General Description
The RT8206A/B dual step-down, switch-mode power-
supply (SMPS) controller generates logic-supply voltages
in battery-powered systems. The RT8206A/B includes two
pulse-width modulation (PWM) controllers fixed at 5V/
3.3V or adjustable from 2V to 5.5V. An optional external
charge pump can be monitored through SECFB
(RT8206A). This device also features a linear regulator
providing a fixed 5V output. The linear regulator provides
up to 70mA output current with automatic linear-regulator
bootstrapping to the BYP input. The RT8206A/B includes
on-board power-up sequencing, the power-good outputs,
internal soft-start, and internal soft-discharge output that
prevents negative voltages on shutdown.
A constant on-time PWM control scheme operates without
sense resistors and provides 100ns response to load
transients while maintaining a relatively constant switching
frequency. The unique ultrasonic mode maintains the
switching frequency above 25kHz, which eliminates noise
in audio applications. Other features include diode-
emulation mode (DEM), which maximizes efficiency in
light-load applications, and fixed-frequency PWM mode,
which reduces RF interference in sensitive application.
The RT8206A/B is available in the WQFN-32L 5x5
package.
Applications
z Notebook and Sub-Notebook Computers
z 3-Cell and 4-Cell Li+ Battery-Powered Devices
Features
z Wide Input Voltage Range 6V to 25V
z Dual Fixed 5V/3.3V Outputs or Adjustable from 2V
to 5.5V, 1.5% Accuracy
z Secondary Feedback Input Maintains Charge Pump
Voltage (RT8206A)
z Independent Enable and Power Good
z 5V Fixed LDO Output : 70mA
z 2V Reference Voltage ±1% : 50uA
z Constant ON-Time Control with 100ns Load Step
Response
z Frequency Selectable via TON Setting
z RDS(ON) Current Sensing and Programmable Current
Limit
z Selectable PWM, DEM or Ultrasonic Mode
z Internal Soft-Start with 5 Steps Current Limiting and
Soft-Discharge
z High Efficiency Up to 97%
z 5mW Quiescent Power Dissipation
Thermal Shutdownzhttp://www.DataSheet4U.net/
z RoHS Compliant and Halogen Free
Ordering Information
RT8206
Package Type
QW : WQFN-32L 5x5 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
A : With SECFB
B : Without SECFB
Richtek Green products are :
` RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
DS8206A/B-04 March 2011
www.richtek.com
1
datasheet pdf - http://www.DataSheet4U.net/






RT8206B Datasheet, Funktion
RT8206A/B
BOOT1 (Pin 17)
Boost Flying Capacitor Connection for SMPS1. Connect
to an external capacitor according to the typical application
circuits.
PHASE2 (Pin 25)
Inductor Connection for SMPS2. PHASE2 is the internal
lower supply rail for the UGATE2 high-side gate driver.
PHASE2 is the current-sense input for the SMPS2.
LGATE1 (Pin 18)
SMPS1 Synchronous-Rectifier Gate-drive Output. LGATE1
swings between PGND and PVCC.
UGATE2 (Pin 26)
High-Side MOSFET Floating Gate-Driver Output for
SMPS2. UGATE2 swings between PHASE2 and BOOT2.
PVCC (Pin 19)
PVCC is the supply voltage for the low-side MOSFET
driver LGATEx. Connect a 5V power source to the PVCC
pin (bypass with 1uF MLCC capacitor to PGND if
necessary). There is an internal 10Ω connecting from
PVCC to VCC. Make sure that both VCC and PVCC are
bypassed with 1uF MLCC capacitors.
EN2 (Pin 27)
SMPS2 Enable Input. The SMPS2 will be enabled if EN2
is greater than the logic high level and be disabled if EN2
is less than the logic low level. If EN2 is connected to
REF, the SMPS2 starts after the SMPS1 reaches
regulation (delay start). Drive EN2 below 0.8V to clear
fault level and reset the fault latches.
SECFB (Pin 20) (RT8206A)
The SECFB is used to monitor the optional external 14V
charge pump. Connect a resistive voltage-divider from the
14V charge pump output to GND to detect the output. If
SECFB drops below the threshold voltage, LGATE1 will
be turned on for 300ns. This will refresh the external charge
pump driven by LGATE1 without over-discharging the
output voltage.
NC (Pin 20) (RT8206B)
No Internal Connection.
GND [Pin 21, Exposed Pad (33)]
Analog Ground for both SMPS and LDO. The exposed
pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
PGND (Pin 22)
Power Ground for SMPS controller. Connect PGND
externally to the underside of the exposed pad.
PGOOD2 (Pin 28)
SMPS2 Power-Good Open-Drain Output. PGOOD2 is low
when the SMPS2 output voltage is more than 7.5% below
the normal regulation point or during soft-start. PGOOD2
is high impedance when the output is in regulation and
the soft-start circuit has terminated. PGOOD2 is low in
shutdown.
http://www.DataSheet4U.net/
SKIP (Pin 29)
SMPS Operation Mode Control.
SKIP = GND : DEM operation
SKIP = REF : Ultrasonic Mode operation
SKIP = VCC : PWM operation.
VOUT2 (Pin 30)
SMPS2 Output Voltage-Sense Input. Connect this pin to
the SMPS2 output. VOUT2 is an input to the constant
on-time-PWM one-shot circuit. It also serves as the
SMPS2 feedback input in fixed-voltage mode.
LGATE2 (Pin 23)
SMPS2 Synchronous-Rectifier Gate-drive Output. LGATE2
swings between PGND and PVCC.
BOOT2 (Pin 24)
Boost Flying Capacitor Connection for SMPS2. Connect
this pin to an external capacitor according to the typical
application circuits.
www.richtek.com
6
ILIM2 (Pin 31)
SMPS2 Current-Limit Adjustment. The GND PHASE2
current-limit threshold is 1/10th the voltage seen at ILIM2
over a 0.5V to 2V range. There is an internal 5uA current
source from VCC to ILIM2. The logic current limit threshold
is default to 100mV value if ILIM2 is higher than (VCC
1V).
DS8206A/B-04 March 2011
datasheet pdf - http://www.DataSheet4U.net/

6 Page









RT8206B pdf, datenblatt
RT8206A/B
Typical Operating Characteristics
VOUT1 Efficiency vs. Load Current
100
90 DEM Mode
80
70
60 Ultrasonic Mode
50 PWM Mode
40
30
20
10
0
0.001
VIN = 7V, TON = VCC,
EN2 = GND, EN1 = VCC,
ENLDO = VIN, FB1 = GND
0.01 0.1
1
Load Current (A)
10
VOUT1 Efficiency vs. Load Current
100
90 DEM Mode
80
70
60
Ultrasonic Mode
50
40
PWM Mode
30
20
10
0
0.001
VIN = 12V, TON = VCC,
EN2 = GND, EN1 = VCC,
ENLDO = VIN, FB1 = GND
0.01 0.1
1
Load Current (A)
10
VOUT1 Efficiency vs. Load Current
100
90
DEM Mode
80
70
60
50
Ultrasonic Mode
40
PWM Mode
30
20
10
0
0.001
VIN = 25V, TON = VCC,
EN2 = GND, EN1 = VCC,
ENLDO = VIN, FB1 = GND
0.01 0.1
1
Load Current (A)
10
http://www.DataSheet4U.net/
VOUT2 Efficiency vs. Load Current
100
90
80 DEM Mode
70
60
50 Ultrasonic Mode
40
PWM Mode
30
20
10
0
0.001
VIN = 12V, TON = VCC,
EN2 = VCC, EN1 = GND,
ENLDO = VIN, FB2 = GND
0.01 0.1
1
Load Current (A)
10
VOUT2 Efficiency vs. Load Current
100
90 DEM Mode
80
70
60
50 Ultrasonic Mode
40 PWM Mode
30
20
10
0
0.001
VIN = 7V, TON = VCC,
EN2 = VCC, EN1 = GND,
ENLDO = VIN, FB2 = GND
0.01
0.1
1
Load Current (A)
10
VOUT2 Efficiency vs. Load Current
100
90
80
70 DEM Mode
60
50 Ultrasonic Mode
40
PWM Mode
30
20
10
0
0.001
VIN = 25V, TON = VCC,
EN2 = VCC, EN1 = GND,
ENLDO = VIN, FB2 = GND
0.01
0.1
1
Load Current (A)
10
www.richtek.com
12
DS8206A/B-04 March 2011
datasheet pdf - http://www.DataSheet4U.net/

12 Page





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