RICHTEK RT8205A

®
RT8205A/B/C
High Efficiency, Main Power Supply Controllers
for Notebook Computers
General Description
Features
The RT8205A/B/C dual step-down, switch-mode powersupply controller generates logic-supply voltages in
battery-powered systems. The RT8205A/B/C includes two
pulse-width modulation (PWM) controllers fixed at 5V/
3.3V or adjustable from 2V to 5.5V. An alternative LGATE1
output LG1_CP can be used for external charge pump
(RT8205B). And an optional external charge pump can be
monitored through SECFB (RT8205C). This device also
features 2 linear regulators providing fixed 5V and 3.3V
outputs. The linear regulator each provides up to 70mA
output current with automatic linear-regulator bootstrapping
to the PWM outputs. The RT8205A/B/C includes on-board
power-up sequencing, the power-good output, internal softstart, and internal soft-discharge output that prevents
negative voltages on shutdown.
z
A constant on-time PWM control scheme operates without
sense resistor 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 diodeemulation mode (DEM), which maximizes efficiency in
light-load applications, and fixed-frequency PWM mode,
which reduces RF interference in sensitive application
z
z
z
z
z
z
z
z
z
z
z
z
z
z
Wide Input Voltage Range 6V to 25V
Dual Fixed 5V/3.3V Outputs or Adjustable from 2V
to 5.5V, 1.5% Accuracy.
Alternative LGATE1 Output (LG1_CP) acts as Clock
for Charge Pump (RT8205B)
Secondary Feedback Input Maintains Charge Pump
Voltage (RT8205C)
Fixed 3.3V and 5V LDO Output : 70mA
2V Reference Voltage ±1% : 50μ
μA
Constant ON-Time Control with 100ns Load Step
Response
Frequency Selectable via TONSEL Setting
RDS(ON) Current Sensing and Programmable Current
Limit combined with Enable Control
Selectable PWM, DEM, or Ultrasonic Mode
Internal Soft-Start and Soft-Discharge
High Efficiency up to 97%
5mW Quiescent Power Dissipation
Thermal Shutdown
RoHS Compliant and Halogen Free
Applications
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Notebook and Sub-Notebook Computers
3-Cell and 4-Cell Li+ Battery-Powered Devices
Ordering Information
RT8205
Package Type
QW : WQFN-24L 4x4 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Pin Function
A : Default
B : With LG1_CP
C : With SECFB
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS8205A/B/C-06 July 2012
Note :
Richtek products are :
`
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
`
Suitable for use in SnPb or Pb-free soldering processes.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
RT8205A/B/C
Marking Information
RT8205AGQW
RT8205CGQW
RT8205BGQW
CK= : Product Code
CJ= : Product Code
YMDNN : Date Code
CJ=YM
DNN
CL= : Product Code
YMDNN : Date Code
CK=YM
DNN
YMDNN : Date Code
CL=YM
DNN
Pin Configurations
24 23 22 21 20 19
ENTRIP1
FB1
REF
TONSEL
FB2
ENTRIP2
24 23 22 21 20 19
1
18
2
17
3
15
25
5
NC
VREG5
VIN
GND
SKIPSEL
EN
16
GND
4
14
13
6
18
2
17
3
16
GND
4
15
25
5
14
6
10 11 12
13
7
8
9
LG1_CP
VREG5
VIN
PGND
SKIPSEL
EN
ENTRIP1
FB1
REF
TONSEL
FB2
ENTRIP2
1
18
2
17
3
15
25
5
SECFB
VREG5
VIN
PGND
SKIPSEL
EN
16
GND
4
14
6
13
10 11 12
7
8
9
10 11 12
VOUT2
VREG3
BOOT2
UGATE2
PHASE2
LGATE2
9
24 23 22 21 20 19
1
VOUT2
VREG3
BOOT2
UGATE2
PHASE2
LGATE2
8
ENTRIP1
FB1
REF
TONSEL
FB2
ENTRIP2
VOUT2
VREG3
BOOT2
UGATE2
PHASE2
LGATE2
7
VOUT1
PGOOD
BOOT1
UGATE1
PHASE1
LGATE1
VOUT1
PGOOD
BOOT1
UGATE1
PHASE1
LGATE1
VOUT1
PGOOD
BOOT1
UGATE1
PHASE1
LGATE1
(TOP VIEW)
RT8205A
RT8205B
RT8205C
WQFN-24L 4x4
WQFN-24L 4x4
WQFN-24L 4x4
Typical Application Circuit
For Fixed Voltage Regulator
VIN
R7
3.9
C1
10uF
C6
0.1uF
Q1
BSC119
N03S
VOUT1
5V
C3
220uF
R5
C4
BOOT2
PHASE2 11
R3 0
22 BOOT1
LGATE2 12
20 PHASE1
19 LGATE1
C11
0.22uF
24 VOUT1
3 REF
Frequency Control
4 TONSEL
PWM/DEM/Ultrasonic
14 SKIPSEL
OFF
13 EN
2 FB1
5 FB2
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
9
21 UGATE1
Q3
BSC119
N03S
ON
UGATE2 10
R4 0
C2
0.1uF
L1
6.8uH
RT8205A
16 VIN
VOUT2 7
VREG5 17
PGOOD 23
VREG3 8
R9
0
Q2
BSC119
N03S
R8 0
C7
0.1uF
GND
R10
VOUT2
3.3V
C13
220uF
C10
5V Always On
R6
100k
PGOOD Indicator
C12
4.7uF
ENTRIP1 1
ENTRIP2
C8
10uF
L2
4.7uH
Q4
BSC119
N03S
C5
4.7uF
C9
10uF
6
3.3V Always On
R1
150k
R2
150k
15, Exposed Pad (25)
is a registered trademark of Richtek Technology Corporation.
DS8205A/B/C-06 July 2012
RT8205A/B/C
VIN
R7
3.9
C1
10uF
RT8205B
C10
0.1uF
Q1
BSC119
N03S
VOUT1
5V
C3
220uF
C4
C6
0.1uF
PHASE2 11
R3 0
22 BOOT1
LGATE2 12
20 PHASE1
18 LG1_CP
C7
0.1uF
C15
0.22uF
D4
ON
BAT254
C8
0.1uF
PGOOD 23
VREG3 8
24 VOUT1
D2
D3
VOUT2 7
VREG5 17
19 LGATE1
C5
0.1uF
D1
9
21 UGATE1
Q3
BSC119
N03S
R5
BOOT2
R4 0
C2
0.1uF
L1
6.8uH
UGATE2 10
16 VIN
ENTRIP2
PGND
13 EN
OFF
CP
ENTRIP1
3 REF
Frequency Control
4 TONSEL
PWM/DEM/Ultrasonic
14 SKIPSEL
R9
0
Q2
BSC119
N03S
R8 0
C7
0.1uF
C12
10uF
L2
4.7uH
Q4
BSC119
N03S
C9
4.7uF
C13
10uF
VOUT2
3.3V
C17
220uF
R10
C14
5V Always On
R6
100k
PGOOD Indicator
C16
4.7uF
3.3V Always On
1
R1
150k
6
R2
150k
15
FB1 2
FB2 5
GND
Exposed Pad (25)
VIN
R8
3.9
C1
10uF
RT8205C
C10
0.1uF
Q1
BSC119
N03S
VOUT1
C3
220uF
C4
D1
C6
0.1uF
R3 0
22 BOOT1
LGATE2 12
20 PHASE1
19 LGATE1
24 VOUT1
C15
0.22uF
D3
C7
0.1uF
BAT254
CP
VOUT2 7
VREG5 17
PGOOD 23
VREG3 8
ENTRIP1 1
ENTRIP2
6
Q2
BSC119
N03S
R9 0
C11
0.1uF
C12
10uF
L2
4.7uH
Q4
BSC119
N03S
C9
4.7uF
C13
10uF
R11
VOUT2
3.3V
C17
220uF
C14
5V Always On
R6
100k
PGOOD Indicator
C16
4.7uF
3.3V Always On
R1
150k
R2
150k
TONSEL 4
R6
200k
C18
ON
3 REF
2 FB1
5 FB2
D4
C8
0.1uF
9
PHASE2 11
C5
0.1uF
D2
BOOT2
21 UGATE1
Q3
BSC119
N03S
R5
UGATE2 10
R4 0
C2
0.1uF
L1
6.8uH
16 VIN
R10
0
18 SECFB
R7
39k
13 EN
Frequency Control
SKIPSEL 14
PWM/DEM/Ultrasonic
15
PGND
Exposed Pad (25)
GND
OFF
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS8205A/B/C-06 July 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
3
RT8205A/B/C
For Adjustable Voltage Regulator
V IN
R7
3.9
C1
10uF
C3
220uF
C4
C15
0.1uF
21 UGATE1
PHASE2 11
R3 0
22 BOOT1
LGATE2 12
20 PHASE1
R11
15k
ENTRIP2
R12
10k
2 FB1
3 REF
C11
0.22uF
Frequency Control
4 TONSEL
PWM/DEM/Ultrasonic
14 SKIPSEL
GND
ON
C13
220uF
C10
C17
R13
6.5k
C16
0.1uF
R14
10k
R2
150k
6
V OUT2
3.3V
R10
R1
150k
15, Exposed Pad (25)
VREG5 17
5V Always On
C5
4.7uF
PGOOD 23
VREG3 8
13 EN
C8
10uF
L2
4.7uH
Q4
BSC119
N03S
ENTRIP1 1
24 VOUT1
C9
10uF
C7
0.1uF
VOUT2 7
5
FB2
19 LGATE1
Q2
BSC119
N03S
R8 0
9
R4 0
Q3
BSC119
N03S
R5
C14
BOOT2
C2
0.1uF
L1
6.8uH
V OUT1
5V
UGATE2 10
16 VIN
C6
0.1uF
Q1
BSC119
N03S
R9
0
RT8205A
R6
100k
PGOOD Indicator
3.3V Always On
C12
4.7uF
OFF
V IN
R7
3.9
C1
10uF
RT8205B
C10
0.1uF
Q1
BSC119
N03S
C3
220uF
C4
C18
C19
0.1uF
BOOT2
PHASE2 11
R3 0
22 BOOT1
LGATE2 12
20 PHASE1
19 LGATE1
R11
15k
2 FB1
D1
C6
0.1uF
C5
0.1uF
18 LG1_CP
D2
D3
C7
0.1uF
3 REF
C15
0.22uF
D4
BAT254
C8
0.1uF
CP
ON
OFF
13 EN
Frequency Control
4 TONSEL
PWM/DEM/Ultrasonic
14 SKIPSEL
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
www.richtek.com
4
R9
0
Q2
BSC119
N03S
R8 0
C7
0.1uF
C13
10uF
C12
10uF
L2
4.7uH
Q4
BSC119
N03S
V OUT2
3.3V
C17
220uF
R10
C14
VOUT2 7
R13
6.5k
FB2 5
24 VOUT1
R12
10k
9
21 UGATE1
Q3
BSC119
N03S
R5
UGATE2 10
R4 0
C2
0.1uF
L1
6.8uH
V OUT1
5V
16 VIN
R1
150k
ENTRIP1 1
ENTRIP2
GND
C20
0.1uF
R2
150k
6
Exposed Pad (25)
VREG5 17
PGOOD 23
VREG3 8
PGND
R14
10k
C21
C9
4.7uF
5V Always On
R6
100k
PGOOD Indicator
C16
4.7uF
3.3V Always On
15
is a registered trademark of Richtek Technology Corporation.
DS8205A/B/C-06 July 2012
RT8205A/B/C
VIN
R8
3.9
C1
10uF
RT8205C
C10
0.1uF
Q1
BSC119
N03S
VOUT1
C3
220uF
C4
C18
C19
0.1uF
BOOT2
PHASE2 11
R3 0
22 BOOT1
LGATE2 12
20 PHASE1
19 LGATE1
R12
15k
2 FB1
D1
C6
0.1uF
C5
0.1uF
D2
D3
C7
0.1uF
3 REF
BAT254
C8
0.1uF
18
R7
39k
CP
SECFB
C18
ON
13 EN
R9 0
C11
0.1uF
C12
10uF
L2
4.7uH
Q4
BSC119
N03S
VOUT2
3.3V
C17
220uF
R11
C14
ENTRIP2
R14
6.5k
5
1
R1
150k
6
R2
150k
R15
10k
C21
C20
0.1uF
Exposed Pad (25)
VREG5 17
PGOOD 23
VREG3 8
D4
R6
200k
ENTRIP1
GND
C15
0.22uF
Q2
BSC119
N03S
C13
10uF
VOUT2 7
FB2
24 VOUT1
R13
10k
9
21 UGATE1
Q3
BSC119
N03S
R5
UGATE2 10
R4 0
C2
0.1uF
L1
6.8uH
16 VIN
R10
0
TONSEL 4
SKIPSEL 14
15
PGND
C9
4.7uF
5V Always On
R6
100k
PGOOD Indicator
C16
4.7uF
3.3V Always On
Frequency Control
PWM/DEM/Ultrasonic
OFF
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS8205A/B/C-06 July 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
RT8205A/B/C
Function Block Diagram
TONSEL SKIPSEL
BOOT1
BOOT2
UGATE1
UGATE2
PHASE1
VREG5
PHASE2
VREG5
SMPS1
PWM Buck
Controller
LGATE1
SMPS2
PWM Buck
Controller
LGATE2
PGND
VOUT2
FB2
ENTRIP2
VOUT1
FB1
ENTRIP1
PGOOD
Power-On
Sequence
Clear Fault Latch
EN
GND
SW Threshold
SW Threshold
Thermal
Shutdown
VREG3
VREG5
REF
VREG5
VREG3
VIN
REF
Function Block Diagram
TONSEL
VIN
UGATE
On-Time
Compute
VOUT
TON
Q
1-Shot
R
TOFF
TRIG 1-Shot
Q
TRIG
REF
- Comp
+
+ -
+
LGATE
FB
1.1 x VREF
0.7 x VREF
Over-Voltage
+
Fault
Latch
-
VREG5
Blanking
+
Time
Under-Voltage
+
0.9 x VREF
+
PGOOD
ENTRIP
-
SS
Time
+
+
25kHz
Detector Zero
Detector
+
Current
Limit
PHASE
-
SKIPSEL
PWM Controller (One Side)
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
www.richtek.com
6
is a registered trademark of Richtek Technology Corporation.
DS8205A/B/C-06 July 2012
RT8205A/B/C
Functional Pin Description
ENTRIP1 (Pin 1)
Channel 1 enable and Current Limit setting Input. Connect
resistor to GND to set the threshold for channel 1
synchronous RDS(ON) sense. The GND-PHASE1 current-
from VREG5 to ENTRIP2. The logic current limit threshold
is default to 200mV value if ENTRIP2 is higher than
VREG5-1V.
limit threshold is 1/10th the voltage seen at ENTRIP1 over
a 0.5V to 2V range. There is an internal 10uA current source
from VREG5 to ENTRIP1. The logic current limit threshold
is default to 200mV value if ENTRIP1 is higher than
VREG5-1V.
VOUT2 (Pin 7)
FB1 (Pin 2)
VREG3 (Pin 8)
SMPS1 Feedback Input. Connect FB1 to VREG5 or GND
for fixed 5V operation. Or connect FB1 to a resistive voltagedivider from VOUT1 to GND to adjust output from 2V to
5.5V.
3.3V Linear Regulator Output.
REF (Pin 3)
2V Reference Output. Bypass to GND with a 0.22uF
capacitor. REF can source up to 50uA for external loads.
Loading REF degrades FBx and output accuracy according
to the REF load-regulation error.
SMPS2 Output Voltage-Sense Input. Connect to the
SMPS2 output. VOUT2 is an input to the on-time oneshot circuit. It also serves as the SMPS2 feedback input
in fixed-voltage mode.
BOOT2 (Pin 9)
Boost Flying Capacitor Connection for SMPS2. Connect
to an external capacitor according to the typical application
circuits.
UGATE2 (Pin 10)
High-Side MOSFET Floating Gate-Driver Output for
SMPS2. UGATE2 swings between PHASE2 and BOOT2.
TONSEL (Pin 4)
PHASE2 (Pin 11)
Frequency Selectable Input for VOUT1/VOUT2
respectively.
Inductor Connection for SMPS2. PHASE2 is the internal
lower supply rail for the UGATE2 high-side gate driver.
PHASE2 is also the current-sense input for the SMPS2.
400kHz/500kHz : Connect to VREG5 or VREG3
300kHz/375kHz : Connect to REF
LGATE2 (Pin 12)
200kHz/250kHz : Connect to GND
SMPS2 Synchronous-Rectifier Gate-Drive Output.
LGATE2 swings between GND and VREG5.
FB2 (Pin 5)
SMPS2 Feedback Input. Connect FB2 to VREG5 or GND
for fixed 3.3V operation. Or connect FB2 to a resistive
voltage-divider from VOUT2 to GND to adjust output from
2V to 5.5V.
EN (Pin 13)
Master Enable Input. The REF/VREG5/VREG3 are
enabled if it is within logic high level and disable if it is
less than the logic low level.
ENTRIP2 (Pin 6)
SKIPSEL (Pin 14)
Channel 2 enable and Current Limit setting Input. Connect
Operation Mode Selectable Input.
resistor to GND to set the threshold for channel 2
synchronous RDS(ON) sense. The GND-PHASE2 currentlimit threshold is 1/10th the voltage seen at ENTRIP2 over
a 0.5V to 2V range. There is an internal 10uA current source
Ultrasonic Mode : Connect to VREG5 or VREG3
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS8205A/B/C-06 July 2012
Diode Emulation Mode : Connect to REF
PWM Mode : Connect to GND
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
7
RT8205A/B/C
GND [Pin 15 (RT8205A), Exposed Pad (25)]
UGATE1 (Pin 21)
Analog Ground for SMPS controller. The exposed pad
must be soldered to a large PCB and connected to GND
for maximum power dissipation.
High-Side MOSFET Floating Gate-Driver Output for
SMPS1. UGATE1 swings between PHASE1 and BOOT1.
BOOT1 (Pin 22)
PGND (Pin 15) (RT8205B/C)
Power Ground for SMPS controller. Connect PGND
externally to the underside of the exposed pad.
Boost Flying Capacitor Connection for SMPS1. Connect
to an external capacitor according to the typical application
circuits.
VIN (Pin 16)
PGOOD (Pin 23)
High Voltage Power Supply Input for 5V/3.3V LDO and
Feed-forward ON-Time circuitry.
Power Good Output for channel 1 and channel 2. (Logical
AND)
VREG5 (Pin 17)
VOUT1 (Pin 24)
5V Linear Regulator Output.VREG5 is also the supply
voltage for the low-side MOSFET driver and analog supply
voltage for the device.
SMPS1 Output Voltage-Sense Input. Connect to the
SMPS1 output. VOUT1 is an input to the on-time oneshot circuit. It also serves as the SMPS1 feedback input
in fixed-voltage mode.
NC (Pin 18) (RT8205A)
No Internal Connection.
LG1_CP (Pin 18) (RT8205B)
Alternative LGATE1 Output for 14V charge pump.
SECFB (Pin 18) (RT8205C)
The SECFB is used to monitor the optional external 14V
charge pump. Connect a resistive voltage-divider from 14V
charge pump output to GND to detect the output. If SECFB
drops below the threshold voltage, LGATE1 turns on for
300ns (typ.). This will refresh the external charge pump
driven by LGATE1 without over-discharging the output
voltage.
LGATE1 (Pin 19)
SMPS1 Synchronous-Rectifier Gate-Drive Output.
LGATE1 swings between GND and VREG5.
PHASE1 (Pin 20)
Inductor Connection for SMPS1. PHASE1 is the internal
lower supply rail for the UGATE1 high-side gate driver.
PHASE1 is also the current-sense input for the SMPS1.
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
www.richtek.com
8
is a registered trademark of Richtek Technology Corporation.
DS8205A/B/C-06 July 2012
RT8205A/B/C
Absolute Maximum Ratings
(Note 1)
VIN, EN to GND ----------------------------------------------------------------------------------------------z PHASEx to GND
DC ---------------------------------------------------------------------------------------------------------------< 20ns ---------------------------------------------------------------------------------------------------------z BOOTx to PHASEx -----------------------------------------------------------------------------------------z ENTRIPx, SKIPSEL, TONSEL, PGOOD, to GND ---------------------------------------------------z VREG5, VREG3, FBx, VOUTx, SECFB, REF to GND --------------------------------------------z UGATEx to PHASEx
DC ---------------------------------------------------------------------------------------------------------------< 20ns ---------------------------------------------------------------------------------------------------------z LGATEx to GND
DC ---------------------------------------------------------------------------------------------------------------< 20ns ---------------------------------------------------------------------------------------------------------z Power Dissipation, PD @ TA = 25°C
WQFN-24L 4x4 ----------------------------------------------------------------------------------------------z Package Thermal Resistance (Note 2)
WQFN-24L 4x4, θJA -----------------------------------------------------------------------------------------WQFN-24L 4x4, θJC ----------------------------------------------------------------------------------------z Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------z Junction Temperature ---------------------------------------------------------------------------------------z Storage Temperature Range ------------------------------------------------------------------------------z ESD Susceptibility (Note 3)
HBM (Human Body Model) --------------------------------------------------------------------------------z
Recommended Operating Conditions
z
z
z
−0.3V to 28V
−0.3V to 28V
−8V
−0.3V to 6V
−0.3V to 6V
−0.3V to (VREG5 + 0.3V)
−0.3V to (VREG5 + 0.3V)
−5V
−0.3V to (VREG5 + 0.3V)
−2.5V
1.923W
52°C/W
7°C/W
260°C
150°C
−65°C to 150°C
2kV
(Note 4)
Input Voltage, VIN -------------------------------------------------------------------------------------------- 6V to 25V
Junction Temperature Range ------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range ------------------------------------------------------------------------------- −40°C to 85°C
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS8205A/B/C-06 July 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
9
To be continued
RT8205A/B/C
Electrical Characteristics
(VIN = 12V, EN = 5V, ENTRIP1 = ENTRIP2 = 2V, No Load on VREG5, VREG3, VOUT1, VOUT2 and REF, TA = 25°C, unless
otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Input Supply
VIN Standby Supply
Current
VIN Shutdown Supply
Current
Quiescent Power
Consumption
IVIN_SBY
VIN = 6V to 25V, Both SMPS Off,
EN = 5V
--
200
--
μA
IVIN_SHDH
VIN = 6V to 25V, ENTRIPx = EN = GND
--
20
40
μA
Both SMPSs On, FBx = SKIPSEL = REF
(Note 5)
VOUT1 = 5.3V, VOUT2 = 3.5V
--
5
7
mW
4.975
5.05
5.125
V
3.285
3.33
3.375
V
1.975
2
2.025
V
1.92
2
2.08
V
2
--
5.5
V
Fixed or Adj-Mode comparator threshold
0.2
0.4
0.55
V
Either SMPS, SKIPSEL = GND, 0 to 5A
Either SMPS, SKIPSEL = VREG5, 0 to 5A
Either SMPS, SKIPSEL = REF, 0 to 5A
Either SMPS, VIN = 6V to 25V
-----
−0.1
−1.7
−1.5
0.005
-----
%
%
%
%/V
1895
2105
2315
SMPS Output and FB Voltage
VOUT1 Output Voltage in
Fixed Mode
VOUT2 Output Voltage in
Fixed Mode
FBx in Output Adjustable
Mode
SECFB Voltage
Output Voltage Adjust
Range
FBx Adjustable-mode
Threshold Voltage
VOUT1
VOUT2
VIN = 6V to 25V, FB1= GND or 5V,
SKIPSEL = GND
VIN = 6V to 25V, FB2 = GND or 5V,
SKIPSEL = GND
FBx
VIN = 6V to 25V
SECFB
VIN = 6V to 25V (RT8205C)
VOUTx
SMPS1, SMPS2
DC Load Regulation
VLOAD
Line Regulation
VLINE
On Time
TONSEL = GND
On-Time Pulse Width
tUGATEx
VOUT2 = 3.33V
999
1110
1221
VOUT1 = 5.05V
1227
1403
1579
VOUT2 = 3.33V
647
740
833
VOUT1 = 5.05V
895
1052
1209
VOUT2 = 3.33V
475
555
635
200
300
400
ns
SKIPSEL = VREG5 or VREG3
25
33
--
kHz
Zero to Full Limit from ENTRIPx Enable
--
2
--
ms
180
200
220
mV
9.4
10
10.6
μA
--
1600
--
PPM/°C
0.5
--
2
V
TONSEL = REF
TONSEL = VREG5
Minimum Off-Time
Ultrasonic Mode
Frequency
VOUT1 = 5.05V
tLGATEx
ns
Soft Start
Soft-Start Time
tSSx
Current Sense
Current Limit Threshold
VENTRIPx = VREG5, GND−PHASEx
(Default)
ENTRIPx Source Current IENTRIPx
VENTRIPx = 0.9V
ENTRIPx Current
TCIENTRIPx
Temperature Coefficient
ENTRIPx Adjustment
VENTRIPx = IENTRIPx x RENTRIPx
Range
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is a registered trademark of Richtek Technology Corporation.
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RT8205A/B/C
Parameter
Symbol
Test Conditions
VENTRIPx = 0.5V
GND−PHASEx VENTRIPx =1V
Current-Limit Threshold
VENTRIPx =2V
SKIPSEL = VREG5 or REF,
GND−PHASEx
Zero-Current Threshold
Min
Typ
Max
Unit
40
90
50
100
60
110
mV
mV
180
200
220
mV
--
3
--
mV
4.8
5
5.2
V
3.2
3.33
3.46
V
Internal Regulator and Reference
VOUT1 = GND, 6V < VIN < 25V,
0 < IVREG5 < 70mA
VOUT2 = GND, 6V < VIN < 25V,
0 < IVREG3 < 70mA
VREG5 Output Voltage
VVREG5
VREG3 Output Voltage
VVREG3
VREG5 Short Current
IVREG5
VREG5 = GND, VOUT1 = GND
--
175
275
mA
VREG3 Short Current
IVREG3
VREG3 = GND, VOUT2 = GND
--
175
275
mA
4.53
4.66
4.79
V
2.96
3.06
3.16
V
--
1.5
3
Ω
VREG5 Switchover Threshold
to VOUT1
VREG3 Switchover Threshold
to VOUT2
VREGx Switchover Equivalent
Resistance
REF Output Voltage
Rising Edge at VOUT1 Regulation
Point
Rising Edge at VOUT2 Regulation
Point
RSW
VREGx to VOUTx, 10mA
VREF
No External Load
1.98
2
2.02
V
REF Load Regulation
0 < I LOAD < 50uA
--
10
--
mV
REF Sink Current
REF in Regulation
5
--
--
μA
SMPSx off
--
2.5
--
V
Rising Edge
--
4.35
4.5
V
Falling Edge
3.9
4.05
4.25
V
−11
−7.5
−4
%
--
10
--
μs
UVLO
VREG3 UVLO Threshold
VREG5 UVLO Threshold
Power Good
PGOOD Propagation Delay
FBx with Respect to Internal
Reference, Falling Edge,
Hysteresis = 1%
Falling Edge, 50mV Overdrive
PGOOD Leakage Current
High State, Forced to 5.5V
--
--
1
μA
PGOOD Output Low Voltage
ISINK = 4mA
--
--
0.3
V
108
111
115
%
--
10
--
μs
65
70
75
%
--
3
--
ms
--
150
--
°C
--
10
--
°C
PGOOD Threshold
Fault Detection
OVP Trip Threshold
VFB_OVP
FBx with Respect to Internal
Reference
OVP Propagation Delay
UVP Trip Threshold
UVP Shutdown Blanking Time
tSHDN_UVP
FBx with Respect to Internal
Reference
From ENTRIPx Enable
Thermal Shutdown
Thermal Shutdown
TSHDN
Thermal Shutdown Hysteresis
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
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11
RT8205A/B/C
Parameter
VOUT Discharge
VOUTx Discharge Current
Logic Input
Symbol
IDISx
FB1/FB2 Input Voltage
SKIPSEL Input Voltage
ENTRIPx Input Voltage
Test Conditions
Min
Typ
Max
Unit
ENTRIPx = GND, VOUTx = 0.5V
10
60
--
mA
Low Level (Internal Fixed VOUTx)
--
--
0.2
V
High Level (Internal Fixed VOUTx)
4.5
--
--
V
Low Level (PWM Mode)
--
--
0.8
V
REF Level (DEM Mode)
1.8
--
2.3
V
High Level (Ultrasonic Mode)
2.5
--
--
V
SMPS On Level
V
0.35
0.4
0.45
EN Threshold Logic-High
VIH
1
--
--
Voltage
VIL
--
--
0.4
-1.8
2.5
−1
−1
−1
-------
0.8
2.3
-3
1
1
VREG5 to BOOTx
--
20
--
Ω
UGATEx Forced to 2V
--
2
--
A
LGATEx Forced to 2V
--
1.7
--
A
LGATEx Forced to 2V
BOOTx to PHASEx Forced to 5V
LGATEx, High State
LGATEx, Low State
LGATEx Rising
UGATEx Rising
-------
3.3
1.5
2.2
0.6
30
40
-4
5
1.5
---
A
Ω
Logic-Low
TONSEL Setting Voltage
Input Leakage Current
Internal BOOT Switch
Internal Boost Charging
Switch On-Resistance
Power MOSFET Drivers
UGATEx Driver Sink/Source
Current
LGATEx Driver Source
Current
LGATEx Driver Sink Current
UGATEx On-Resistance
LGATEx On-Resistance
Dead Time
VOUT1/VOUT2 = 200kHz/250kHz
VOUT1/VOUT2 = 300kHz/375kHz
VOUT1/VOUT2 = 400kHz/500kHz
EN = 0V or 25V
TONSEL, SKIPSEL = 0V or 5V
FBx = SECFB = 0V or 5V
V
V
μA
Ω
ns
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. PVIN + PVREG5
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is a registered trademark of Richtek Technology Corporation.
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RT8205A/B/C
Typical Operating Characteristics
VOUT1 Output Efficiency vs. Load Current
VOUT2 Output Efficiency vs. Load Current
100
100
90
90
DEM Mode
80
70
Efficiency (%)
Efficiency (%)
80
Ultrasonic Mode
60
50
PWM Mode
40
30
20
DEM Mode
70
60
Ultrasonic Mode
50
PWM Mode
40
30
20
VIN = 8V, TONSEL = GND, EN = VIN,
ENTRIP1 = 0.91V, ENTRIP2 = GND
10
0
0.001
0.01
0.1
1
VIN = 8V, TONSEL = GND, EN = VIN,
ENTRIP1 = GND, ENTRIP2 = 0.91V
10
0
0.001
10
0.01
Load Current (A)
VOUT1 Output Efficiency vs. Load Current
100
90
90
Ultrasonic Mode
60
50
Efficiency (%)
Efficiency (%)
80
DEM Mode
70
PWM Mode
40
30
20
DEM Mode
70
Ultrasonic Mode
60
50
PWM Mode
40
30
0.01
0.1
1
VIN = 12V, TONSEL = GND, EN = VIN,
ENTRIP1 = GND, ENTRIP2 = 0.91V,
10
0
0.001
10
0.01
Load Current (A)
VOUT1 Output Efficiency vs. Load Current
90
90
70
Efficiency (%)
Efficiency (%)
80
DEM Mode
Ultrasonic Mode
50
PWM Mode
40
30
20
0
0.001
70
0.01
0.1
1
Load Current (A)
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DS8205A/B/C-06 July 2012
10
DEM Mode
60
Ultrasonic Mode
50
40
PWM Mode
30
20
VIN = 20V, TONSEL = GND, EN = VIN,
ENTRIP1 = 0.91V, ENTRIP2 = GND
10
1
VOUT2 Output Efficiency vs. Load Current
100
60
0.1
Load Current (A)
100
80
10
20
VIN = 12V, TONSEL = GND, EN = VIN,
ENTRIP1 = 0.91V, ENTRIP2 = GND
10
0
0.001
1
VOUT2 Output Efficiency vs. Load Current
100
80
0.1
Load Current (A)
10
VIN = 20V
TONSEL = GND, EN = VIN,
ENTRIP1 = GND, ENTRIP2 = 0.91V
10
0
0.001
0.01
0.1
1
10
Load Current (A)
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RT8205A/B/C
VOUT1 Output Switching Frequency vs. Load Current
225
300
VIN = 8V, TONSEL = GND, EN = VIN,
ENTRIP1 = 0.91V, ENTRIP2 = GND
275
200
PWM Mode
175
150
125
100
75
50
Ultrasonic Mode
25
VOUT2 Output Switching Frequency vs. Load Current
Switching Frequency (kHz)
Switching Frequency (kHz)
250
0.01
250
PWM Mode
225
200
175
150
125
100
75
Ultrasonic Mode
50
25
DEM Mode
0
0.001
VIN = 8V, TONSEL = GND, EN = VIN,
ENTRIP1 = GND, ENTRIP2 = 0.91V
0.1
1
DEM Mode
0
0.001
10
0.01
Load Current (A)
300
VIN = 12V, TONSEL = GND, EN = VIN,
ENTRIP1 = 0.91V, ENTRIP2 = GND
275
200
PWM Mode
175
150
125
100
75
50
Ultrasonic Mode
25
0
0.001
0.1
250
VIN = 12V, TONSEL = GND, EN = VIN,
ENTRIP1 = GND, ENTRIP2 = 0.91V
PWM Mode
225
200
175
150
125
100
75
Ultrasonic Mode
50
25
DEM Mode
0.01
1
0
0.001
10
DEM Mode
0.01
VOUT1 Output Switching Frequency vs. Load Current
300
VIN = 20V, TONSEL = GND, EN = VIN,
ENTRIP1 = 0.91V, ENTRIP2 = GND
275
200
175
PWM Mode
150
125
100
75
50
Ultrasonic Mode
25
0
0.001
0.1
1
Load Current (A)
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
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14
10
250
VIN = 20V, TONSEL = GND, EN = VIN,
ENTRIP1 = GND, ENTRIP2 = 0.91V
225
PWM Mode
200
175
150
125
100
75
50
Ultrasonic Mode
25
DEM Mode
0.01
1
VOUT2 Output Switching Frequency vs. Load Current
Switching Frequency (kHz)
Switching Frequency (kHz)
225
0.1
Load Current (A)
Load Current (A)
250
10
VOUT2 Output Switching Frequency vs. Load Current
Switching Frequency (kHz)
Switching Frequency (kHz)
225
1
Load Current (A)
VOUT1 Output Switching Frequency vs. Load Current
250
0.1
10
0
0.001
DEM Mode
0.01
0.1
1
10
Load Current (A)
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DS8205A/B/C-06 July 2012
RT8205A/B/C
VOUT1 Output Voltage vs. Load Current
5.114
VIN = 12V, TONSEL = GND, EN = VIN,
ENTRIP1 = 0.91V, ENTRIP2 = GND
Ultrasonic Mode
5.108
5.102
5.096
5.090
DEM Mode
5.084
5.078
5.072
5.066
PWM Mode
5.060
VIN = 12V, TONSEL = GND, EN = VIN,
ENTRIP1 = GND, ENTRIP2 = 0.91V
3.372
3.366
Output Voltage (V)
Output Voltage (V)
VOUT2 Output Voltage vs. Load Current
3.378
Ultrasonic Mode
3.360
3.354
DEM Mode
3.348
3.342
PWM Mode
3.336
3.330
5.054
5.048
0.001
0.01
0.1
1
3.324
0.001
10
0.01
0.1
Load Current (A)
4.978
3.324
VIN = 12V, TONSEL = GND, EN = VIN,
ENTRIP1 = ENTRIP2 = GND
3.322
VIN = 12V, TONSEL = GND, EN = VIN,
ENTRIP1 = ENTRIP2 = GND
3.320
Output Voltage (V)
Output Voltage (V)
4.976
4.974
4.972
4.970
4.968
4.966
3.318
3.316
3.314
3.312
4.964
3.310
4.962
3.308
3.306
4.960
0
10
20
30
40
50
60
0
70
10
20
VREF vs. Output Current
2.0028
Battery Current (mA)
VREF (V)
2.0024
2.0022
2.0020
2.0018
2.0016
2.0014
2.0010
30
40
Output Current (μA)
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS8205A/B/C-06 July 2012
70
10
Ultrasonic Mode
1
DEM Mode
No Load, TONSEL = GND, EN = VIN,
ENTRIP1 = ENTRIP2 = 0.91V
0.1
20
60
PWM Mode
2.0012
10
50
Battery Current vs. Input Voltage
2.0026
0
40
100
VIN = 12V, TONSEL = GND, EN = VIN,
ENTRIP1 = ENTRIP2 = GND
-10
30
Output Current (mA)
Output Current (mA)
2.0030
10
VREG3 Output Voltage vs. Output Current
VREG5 Output Voltage vs. Output Current
4.980
1
Load Current (A)
50
7
9
11
13
15
17
19
21
23
25
Input Voltage (V)
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RT8205A/B/C
Standby Input Current vs. Input Voltage
Shutdown Input Current vs. Input Voltage
22
No Load, EN = VIN, ENTRIP1 = ENTRIP2 = GND
Shutdown Input Current (μA)
Standby Input Current (μA)
252
250
248
246
244
242
No Load, EN = GND, ENTRIP1 = ENTRIP2 = GND
20
18
16
14
12
10
240
8
7
9
11
13
15
17
19
21
23
25
7
9
11
13
15
17
19
Input Voltage (V)
Input Voltage (V)
VREF vs. Temperature
Start Up
21
23
25
2.011
2.008
VREG5
(5V/Div)
VREF (V)
2.005
VREG3
(5V/Div)
2.002
REF
(5V/Div)
1.999
1.996
1.993
EN
(10V/Div)
VIN = 12V, ENTRIP1 = ENTRIP2 = GND,
EN = VIN, TONSEL = GND
No Load, VIN = 12V, TONSEL = GND,
EN = VIN, ENTRIP1 = ENTRIP2 = GND
1.990
-40 -25 -10
5
20
35
50
65
80
Time (400μs/Div)
95 110 125
Temperature (°C)
CP Start Up
VOUT1 Start Up
No Load, VIN = 12V, TONSEL = GND, EN = VIN
No Load, VIN = 12V, TONSEL = GND, EN = VIN
VOUT1
(5V/Div)
VOUT1
(5V/Div)
CP
(5V/Div)
Inductor
Current
(2A/Div)
UGATE1
(20V/Div)
LGATE1
(5V/Div)
ENTRIP1
(2V/Div)
ENTRIP1 = ENTRIP2 = 0.91V, SKIPSEL = REF
Time (400μs/Div)
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16
PGOOD
(10V/Div)
ENTRIP1 = ENTRIP2 = 0.91V
Time (400μs/Div)
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RT8205A/B/C
VOUT2 Start Up
VOUT1 Start Up
No Load, VIN = 12V, TONSEL = GND, EN = VIN
Heavy Load, VIN = 12V, TONSEL = GND, EN = VIN
VOUT2
(5V/Div)
VOUT1
(5V/Div)
Inductor
Current
(2A/Div)
Inductor
Current
(2A/Div)
ENTRIP2
(2V/Div)
ENTRIP1
(2V/Div)
PGOOD
(10V/Div)
ENTRIP1 = NTRIP2 = 0.91V, IOUT1 = 4A
PGOOD
(10V/Div)
Time (400μs/Div)
Time (400μs/Div)
VOUT2 Start Up
VOUT1 Delay Start
No Load, VIN = 12V, TONSEL = GND, EN = VIN
Heavy Load, VIN = 12V, TONSEL = GND, EN = VIN
VOUT2
(5V/Div)
VOUT1
(5V/Div)
Inductor
Current
(2A/Div)
VOUT2
(5V/Div)
ENTRIP1
(1V/Div)
ENTRIP2
(2V/Div)
PGOOD
(10V/Div)
ENTRIP1 = ENTRIP2 = 0.91V
ENTRIP1 = ENTRIP2 = 0.91V
ENTRIP2
(1V/Div)
Time (400μs/Div)
Time (400μs/Div)
VOUT2 Delay Start
VOUT1 PWM Mode Load Transient Response
No Load, VIN = 12V, TONSEL = GND, EN = VIN
VIN = 12V, TONSEL = GND, EN = VIN,
SKIPSEL = GND, IOUT1 = 0A to 6A
VOUT1
(5V/Div)
VOUT1_ac
(50mV/Div)
VOUT2
(5V/Div)
Inductor
Current
(5A/Div)
ENTRIP1
(1V/Div)
UGATE1
(20V/Div)
ENTRIP2
(1V/Div)
LGATE1
(10V/Div)
Time (400μs/Div)
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DS8205A/B/C-06 July 2012
Time (20μs/Div)
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RT8205A/B/C
Power Off from ENTRIP1
VOUT2 PWM Mode Load Transient Response
VIN = 12V, TONSEL = GND, EN = VIN,
SKIPSEL = GND, IOUT2 = 0A to 6A
VOUT2_ac
(50mV/Div)
VOUT1
(5V/Div)
UGATE1
(20V/Div)
Inductor
Current
(5A/Div)
LGATE1
(5V/Div)
UGATE2
(20V/Div)
LGATE2
(10V/Div)
ENTRIP1
(1V/Div)
Time (20μs/Div)
Time (40ms/Div)
OVP
UVP
No Load, VIN = 12V, TONSEL = GND, EN = VIN
SKIPSEL = REF
VOUT1
(5V/Div)
VOUT1
(5V/Div)
VIN = 12V, TONSEL = GND, EN = VIN
SKIPSEL = GND
Inductor
Current
(5A/Div)
VOUT2
(2V/Div)
UGATE1
(20V/Div)
PGOOD
(5V/Div)
LGATE1
(10V/Div)
Time (4ms/Div)
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
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No Load, VIN = 12V, TONSEL = GND, EN = VIN
SKIPSEL = GND
Time (20μs/Div)
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DS8205A/B/C-06 July 2012
RT8205A/B/C
Application Information
The RT8205A/B/C is a dual, Mach ResponseTM DRVTM
dual ramp valley mode synchronous buck controller. The
controller is designed for low-voltage power supplies for
notebook computers. Richtek's Mach Response TM
technology is specifically designed for providing 100ns
“instant-on” response to load steps while maintaining a
relatively constant operating frequency and inductor
operating point over a wide range of input voltages. The
topology circumvents the poor load-transient timing
problems of fixed-frequency current-mode PWMs while
avoiding the problems caused by widely varying switching
frequencies in conventional constant-on-time and constantoff-time PWM schemes. The DRV TM mode PWM
modulator is specifically designed to have better noise
immunity for such a dual output application. The RT8205A/
B/C includes 5V (VREG5) and 3.3V (VREG3) linear
regulators. VREG5 linear regulator can step down the
battery voltage to supply both internal circuitry and gate
drivers. The synchronous-switch gate drivers are directly
powered from VREG5. When VOUT1 voltage is above
4.66V, an automatic circuit will switch the power of the
device from VREG5 linear regulator from VOUT1.
PWM Operation
The Mach ResponseTM DRVTM mode controller relies on
the output filter capacitor's effective series resistance
(ESR) to act as a current-sense resistor, so the output
ripple voltage provides the PWM ramp signal. Refer to the
RT8205A/B/C's function block diagram, the synchronous
high-side MOSFET will be turned on at the beginning of
each cycle. After the internal one-shot timer expires, the
MOSFET will be turned off. The pulse width of this one
shot is determined by the converter's input voltage and
the output voltage to keep the frequency fairly constant
over the input voltage range. Another one-shot sets a
minimum off-time (300ns typ.). The on-time one-shot will
be triggered if the error comparator is high, the low-side
switch current is below the current-limit threshold, and
the minimum off-time one-shot has timed out.
PWM Frequency and On-Time Control
The Mach ResponseTM control architecture runs with
pseudo-constant frequency by feed-forwarding the input
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DS8205A/B/C-06 July 2012
and output voltage into the on-time one-shot timer. The
high-side switch on-time is inversely proportional to the
input voltage as measured by the VIN, and proportional to
the output voltage. There are two benefits of a constant
switching frequency. The first is the frequency can be
selected to avoid noise-sensitive regions such as the
455kHz IF band. The second is the inductor ripple-current
operating point remains relatively constant, resulting in
easy design methodology and predictable output voltage
ripple. The frequency for 3V SMPS is set at 1.25 times
higher than the frequency for 5V SMPS. This is done to
prevent audio-frequency “beating” between the two sides,
which switch asynchronously for each side. The
frequencies are set by TONSEL pin connection as Table1.
The on-time is given by :
On-Time = K x (VOUT / VIN)
where “K” is set by the TONSEL pin connection (Table
1). The on-time guaranteed in the Electrical Characteristics
tables are influenced by switching delays in the external
high-side power MOSFET. Two external factors that
influence switching-frequency accuracy are resistive drops
in the two conduction loops (including inductor and PC
board resistance) and the dead-time effect. These effects
are the largest contributors to the change of frequency
with changing load current. The dead-time effect increases
the effective on-time, reducing the switching frequency
as one or both dead times. It occurs only in PWM mode
(SKIPSEL= GND) when the inductor current reverses at
light or negative load currents. With reversed inductor
current, the inductor's EMF causes PHASEx to go high
earlier than normal, extending the on-time by a period
equal to the low-to-high dead time. For loads above the
critical conduction point, the actual switching frequency
is :
f = (VOUT + VDROP1) / (tON x (VIN + VDROP1 -VDROP2) )
where VDROP1 is the sum of the parasitic voltage drops in
the inductor discharge path, including synchronous
rectifier, inductor, and PC board resistances; VDROP2 is
the sum of the resistances in the charging path; and tON
is the on-time calculated by the RT8205A/B/C.
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RT8205A/B/C
Table 1. TONSEL Connection and Switching
Frequency
SMPS 1
SMPS 1
SMPS 2
TON
K-Factor
Frequency
K-Factor
(μs)
(kHz)
(μs)
GND
5
200
4
REF
3.33
300
2.67
VREG5 or
2.5
400
2
VREG3
TON
GND
REF
VREG5 or
VREG3
SMPS 2
Approximate
Frequency (kHz) K-Factor Error (%)
250
±10
375
±10
500
±10
Operation Mode Selection (SKIPSEL)
The RT8205A/B/C supports three operation modes : DiodeEmulation Mode, Ultrasonic Mode, and Forced-CCM
Mode.
Diode-Emulation Mode (SKIPSEL = REF)
In Diode-Emulation mode, The RT8205A/B/C automatically
reduces switching frequency at light-load conditions to
maintain high efficiency. This reduction of frequency is
achieved smoothly and without increase of VOUT ripple or
load regulation. As the output current decreases from
heavy-load condition, the inductor current is also reduced,
and eventually comes to the point that its valley touches
zero current, which is the boundary between continuous
conduction and discontinuous conduction modes. By
emulating the behavior of diodes, the low-side MOSFET
allows only partial of negative current when the inductor
free-wheeling current reach negative. As the load current
is further decreased, it takes longer and longer to discharge
the output capacitor to the level that requires the next
“ON” cycle. The on-time is kept the same as that in the
heavy-load condition. In reverse, when the output current
increases from light load to heavy load, the switching
frequency increases to the preset value as the inductor
current reaches the continuous conduction. The transition
load point to the light-load operation can be calculated as
follows (Figure 1) :
(VIN − VOUT )
ILOAD(SKIP) ≈
× TON
2L
where Ton is the On-time.
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IL
Slope = (VIN -VOUT) / L
iL, peak
iLoad = iL, peak / 2
0
t
tON
Figure 1. Boundary condition of CCM/DCM
The switching waveforms may appear noisy and
asynchronous when light loading causes Diode-Emulation
operation, but this is a normal operating condition that
results in high light-load efficiency. Trade-offs in PFM noise
vs. light-load efficiency are made by varying the inductor
value. Generally, low inductor values produce a broader
efficiency vs. load curve, while higher values result in higher
full-load efficiency (assuming that the coil resistance
remains fixed) and less output voltage ripple. Penalties
for using higher inductor values include larger physical
size and degraded load-transient response (especially at
low input-voltage levels).
Ultrasonic Mode (SKIPSEL = VREG5 or VREG3)
Connecting SKIPSEL to VREG5 or VREG3 activates a
unique Diode-Emulation mode with a minimum switching
frequency of 25kHz. This ultrasonic mode eliminates
audio-frequency modulation that would otherwise be
present when a lightly loaded controller automatically
skips pulses. In ultrasonic mode, the low-side switch gatedriver signal is OR with an internal oscillator (>25kHz).
Once the internal oscillator is triggered, the ultrasonic
controller pulls LGATEx high, turning on the low-side
MOSFET to induce a negative inductor current. After the
output voltage across the REF, the controller turns off the
low-side MOSFET (LGATEx pulled low) and triggers a
constant on-time (UGATEx driven high). When the ontime has expired, the controller re-enables the low-side
MOSFET until the controller detects that the inductor
current dropped below the zero-crossing threshold.
Forced-CCM Mode (SKIPSEL = GND)
The low-noise, forced-CCM mode (SKIPSEL = GND)
disables the zero-crossing comparator, which controls the
low-side switch on-time. This causes the low-side gateis a registered trademark of Richtek Technology Corporation.
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RT8205A/B/C
driver waveform to become the complement of the highside gate-driver waveform. This in turn causes the inductor
current to reverse at light loads as the PWM loop to
maintain a duty ratio of VOUT/VIN. The benefit of forcedCCM mode is to keep the switching frequency fairly
constant, but it comes at a cost : The no-load battery
current can be 10mA to 40mA, depending on the external
MOSFETs.
characteristic and maximum load capability are a function
of the sense resistance, inductor value, and battery and
output voltage.
IL
IL, peak
ILoad
ILIM
Reference and linear Regulators (REF, VREGx)
The 2V reference (REF) is accurate within ±1% over
temperature, making REF useful as a precision system
reference. Bypass REF to GND with a 0.22uF (min)
capacitor. REF can supply up to 50uA for external loads.
Loading REF reduces the VOUTx output voltage slightly
because of the reference load-regulation error.
VREG5 regulator supplies total of 70mA for internal and
external loads, including MOSFET gate driver and PWM
controller. VREG3 regulator supplies up to 70mA for
external loads. Bypass VREG5 and VREG3 with a 4.7uF
(min) capacitor; use an additional 1uF per 5mA of internal
and external load.
When the 5V main output voltage is above the VREG5
switchover threshold, an internal 1.5Ω N-Channel MOSFET
switch connects VOUT1 to VREG5 while simultaneously
shutting down the VREG5 linear regulator. Similarly, when
the 3.3V main output voltage is above the VREG3
switchover threshold, an internal 1.5Ω N-Channel MOSFET
switch connects VOUT2 to VREG3 while simultaneously
shutting down the VREG3 linear regulator. It can decrease
the power dissipation from the same battery, because the
converted efficiency of SMPS is better than the converted
efficiency of linear regulator.
t
0
Figure 2. “valley” Current-Limit
The RT8205A/B/C uses the on-resistance of the
synchronous rectifier as the current-sense element. Use
the worse-case maximum value for RDS(ON) from the
MOSFET datasheet, and add a margin of 0.5%/°C for the
rise in RDS(ON) with temperature.
The RILIM resistor between the ENTRIPx pin and GND sets
the over current threshold. The resistor RILIM is connected
to a 10uA current source from ENTRIPx. When the voltage
drop across the sense resistor or low-side MOSFET
equals 1/10 the voltage across the RILIM resistor, positive
current limit will be activated. The high-side MOSFET will
not be turned on until the voltage drop across the MOSFET
falls below 1/10 the voltage across the RILIM resistor.
Choose a current limit resistor by following equation :
VILIM = (RILIM x 10uA) / 10 = IILIM x RDS(ON)
RILIM = (IILIM x RDS(ON)) x 10 / 10uA
Carefully observe the PC board layout guidelines to ensure
that noise and DC errors do not corrupt the current-sense
signal at PHASEx and GND. Mount or place the IC close
to the low-side MOSFET.
Current-Limit Setting (ENTRIPx)
Charge Pump (LG1_CP or SECFB)
The RT8205A/B/C has cycle-by-cycle current limiting
control. The current-limit circuit employs a unique “valley”
current sensing algorithm. If the magnitude of the currentsense signal at PHASEx is above the current-limit
threshold, the PWM is not allowed to initiate a new cycle
(Figure 2). The actual peak current is greater than the
current-limit threshold by an amount equal to the inductor
ripple current. Therefore, the exact current-limit
The external 14V charge pump is driven by LGATE1 (Figure
3 and Figure 4). When LGATE1 is low, the C1 will be
charged by D1 from VOUT1. C1 voltage is equal to VOUT1
minus a diode drop. When LGATE1 transitions to high,
the charges from C1 will transfer to C2 through D2 and
charge it to VLGATE1 plus VC1. As LGATE1 transitions low
on the next cycle, C2 will charge C3 to its voltage minus
a diode drop through D3. Finally, C3 charges C4 through
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RT8205A/B/C
D4 when LGATE1 switched to high. So, VCP voltage is :
MOSFET Gate Driver (UGATEx, LGATEx)
VCP = VOUT1 + 2 x VLGATE1 − 4 x VD
The high-side driver is designed to drive high-current, low
RDS(ON) N-MOSFET(s). When configured as a floating driver,
5-V bias voltage is delivered from VREG5 supply. The
average drive current is also calculated by the gate charge
at VGS = 5 V times switching frequency. The instantaneous
drive current is supplied by the flying capacitor between
BOOTx and PHASEx pins. A dead time to prevent shoot
through is internally generated between high-side
MOSFET off to low-side MOSFET on, and low-side
MOSFET off to high-side MOSFET on.
Where VLGATE1 is the peak voltage of LGATE1 driver and is
equal to the VREG5; VD is the forward diode dropped
across the Schottky.
LG1_CP in the RT8205B (Figure 3) can be used as clock
signal for charge pump circuit to generate approximately
14V DC voltage and the clock driver uses VOUT1 as its
power supply, SECFB in the RT8205C is used to monitor
the charge pump through resistive divider (Figure 4). In an
event when SECFB dropped below 2V, the detection circuit
forces the high-side MOSFET off and the low-side
MOSFET on for 300ns to allow CP to recharge and SECFB
rise above 2V. In the event of an overload on CP where
SECFB can not reach more than 2V, the monitor will be
cancelled. Special care should be taken to ensure enough
normal voltage ripple on each cycle as to prevent CP shutdown.
The SECFB pin has ~17mV of hysteresis, so the ripple
should be enough to bring the SECFB voltage above the
threshold by ~3x the hysteresis, or (2V + 3 x 17mV) =
2.051V. Reducing the CP decoupling capacitor and placing
a small ceramic capacitor (10 pF to 47pF) (CF of Figure 4)
in parallel with the upper leg of the SECFB resistor
feedback network (RCP1 of Figure 4) will also increase the
robustness of the charge pump.
The low-side driver is designed to drive high current low
RDS(ON) N-MOSFET(s). The internal pull-down transistor
that drives LGATEx low is robust, with a 0.6Ω typical onresistance. A 5V bias voltage is delivered from VREG5
supply. The instantaneous drive current is supplied by an
input capacitor connected between VREG5 and GND.
For high-current applications, some combinations of highand low-side MOSFETs might be encountered that will
cause excessive gate-drain coupling, which can lead to
efficiency-killing, EMI-producing shoot-through currents.
This is often remedied by adding a resistor in series with
BOOTx, which increases the turn-on time of the high-side
MOSFET without degrading the turn-off time (Figure 5).
V IN
BOOTx
LG1_CP
CP
C3
C1
D2
PHASEx
C4
C2
D1
UGATEx
D4
D3
10
V OUT1
Figure 5. Reducing the UGATEx Rise Time
Figure 3. Connect to LG1_CP
Soft-Start
SECFB
R CP2
LGATE1
CF
C3
C1
D2
D1
D3
R CP1
D4
C2
CP
C4
A build-in soft-start is used to prevent surge current from
power supply input after ENTRIPx is enabled. The typical
soft-start duration is 2ms period. Furthermore, the
maximum allowed current limit is segmented in 5 steps:
20%, 40%, 60%, 80% and 100% during the 2ms period.
V OUT1
Figure 4. Connect to SECFB
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RT8205A/B/C
UVLO Protection
The RT8205A/B/C has VREG5 under voltage lock out
protection (UVLO). When the VREG5 voltage is lower than
4.2V (typ.) and the VREG3 voltage is lower than 2.5V
(typ.), both switch power supplies are also shut off. This
is non-latch protection.
Power-Good Output (PGOOD)
The PGOOD is an open-drain type output and requires a
pull-up resistor. PGOOD is actively held low in soft-start,
standby, and shutdown. It is released when both outputs
voltage above than 92.5% of nominal regulation point. The
PGOOD goes low if either output turns off or is 10% below
its nominal regulator point.
LGATEx gate drivers are forced low while entering softdischarge mode. During soft-start, the UVP will be blanked
around 3ms.
Thermal Protection
The RT8205A/B/C have thermal shutdown to prevent the
overheat damage. Thermal shutdown occurs when the die
temperature exceeds +150°C. All internal circuitry shuts
down during thermal shutdown. The RT8205A/B/C triggers
thermal shutdown if VREGx is not supplied from VOUTx,
while input voltage on VIN and drawing current form VREGx
are too high. Even if VREGx is supplied from VOUTx,
overloading the VREGx causes large power dissipation
on automatic switches, which may result in thermal
shutdown.
Output Over Voltage Protection (OVP)
The output voltage can be continuously monitored for over
voltage. When over voltage protection is enabled, if the
output voltage exceeded 11% of its set voltage threshold,
the over voltage protection is triggered and the LGATEx
low-side gate drivers are forced high. This activates the
low-side MOSFET switch, which rapidly discharges the
output capacitor and pulls the input voltage downward.
RT8205A/B/C is latched once OVP is triggered and can
only be released by EN power-on reset. There is 10us
delay built into the over voltage protection circuit to prevent
false transition.
Note that LGATEx latching high causes the output voltage
to dip slightly negative when energy has been previously
stored in the LC tank circuit. For loads that cannot tolerate
a negative voltage, place a power Schottky diode across
the output to act as a reverse polarity clamp.
If the over voltage condition is caused by a short in highside switch, turning the low-side MOSFET on 100%
creates an electrical short between the battery and GND,
blowing the fuse and disconnecting the battery from the
output.
Output Under voltage Protection (UVP)
The output voltage can be continuously monitored for under
voltage. When under voltage protection is enabled, if the
output is less than 70% of its set voltage threshold, under
voltage protection is triggered, then both UGATEx and
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Discharge Mode (Soft-Discharge)
When ENTRIPx is low and a transition to standby or
shutdown mode occurs, or the output under voltage fault
latch is set, the outputs discharge mode will be triggered.
During discharge mode, there is one path to discharge
the outputs capacitor residual charge. That is output
capacitor discharge to GND through an internal switch.
Shutdown Mode
The RT8205A/B/C SMPS1, SMPS2, VREG3 and VREG5
have independent enabling control. Drive EN, ENTRIP1
and ENTRIP2 below the precise input falling-edge trip level
to place the RT8205A/B/C in its low-power shutdown
state. The RT8205A/B/C consumes only 20uA of input
current while in shutdown.
Power-Up Sequencing and On/Off Controls
(ENTRIPx)
ENTRIP1 and ENTRIP2 control SMPS power-up
sequencing. When the RT8205A/B/C applies in the single
channel mode, ENTRIP1 or ENTRIP2 enables the
respective outputs when ENTRIPx voltage rising above
0.4V.
If both of ENTRIP1 and ENTRIP2 become higher than the
enable threshold voltage at a different time (without 60us),
one can force the latter one output starts after the former
one regulates.
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RT8205A/B/C
Output Voltage Setting (FBx)
Connect FBx directly to GND or VREG5 to enable the
fixed, SMPS output voltages (3.3V and 5V). Connect a
resistor voltage-divider at the FBx between the VOUTx
and GND to adjust the respective output voltage between
2V and 5.5V (Figure 6). Choose R2 to be approximately
10kΩ, and solve for R1 using the equation :
⎡
⎤
VOUTx = VFBx × ⎢1 + ⎛⎜ R1 ⎞⎟ ⎥
R2
⎠⎦
⎣ ⎝
where VFBx is 2V (typ.).
VREG5 connects to VOUT1 through an internal switch
only when VOUT1 is above the VREG5 automatic switch
threshold (4.66V). VREG3 connects to VOUT2 through
an internal switch only when VOUT2 is above the VREG3
automatic switch threshold (3.06V). This is the most
effective way when the fixed output voltages are used.
Once VREGx is supplied from VOUTx, the internal linear
regulator turns off. This reduces internal power dissipation
and improves efficiency when the VREGx is powered with
a high input voltage.
VIN
VOUTx
UGATEx
Find a low-loss inductor having the lowest possible DC
resistance that fits in the allotted dimensions. Ferrite cores
are often the best choice, although powdered iron is
inexpensive and can work well at 200kHz. The core must
be large enough not to saturate at the peak inductor current
(IPEAK) :
IPEAK = ILOAD(MAX) + [(LIR / 2) x ILOAD(MAX)]
This inductor ripple current also impacts transient-response
performance, especially at low VIN − VOUTx differences.
Low inductor values allow the inductor current to slew
faster, replenishing charge removed from the output filter
capacitors by a sudden load step. The peak amplitude of
the output transient VSAG is also a function of the output
transient. The VSAG also features a function of the
maximum duty factor, which can be calculated from the
on-time and minimum off-time :
VSAG
V
(ΔILOAD )2 × L × ⎛⎜ K OUTx + TOFF(MIN) ⎞⎟
VIN
⎝
⎠
=
⎡ ⎛ VIN − VOUTx ⎞
⎤
2 × COUT × VOUTx × ⎢K ⎜
⎟ − TOFF(MIN) ⎥
V
IN
⎝
⎠
⎣
⎦
Where minimum off-time (TOFF(MIN)) = 300ns (typ.) and K
is from Table 1.
PHASEx
LGATEx
VOUTx
FBx
PGND
R1
R2
GND
Figure 6. Setting VOUTx with a Resistor-Divider
Output Inductor Selection
The switching frequency (on-time) and operating point (%
ripple or LIR) determine the inductor value as shown as
follows :
L=
TON × (VIN − VOUTx )
LIR × ILOAD(MAX)
Output Capacitor Selection
The output filter capacitor must have low enough ESR to
meet output ripple and load-transient requirements, yet
have high enough ESR to satisfy stability requirements.
Also, the capacitance value must be high enough to
absorb the inductor energy going from a full-load to noload condition without tripping the OVP circuit.
For CPU core voltage converters and other applications
where the output is subject to violent load transients, the
output capacitor's size depends on how much ESR is
needed to prevent the output from dipping too low under a
load transient. Ignoring the sag due to finite capacitance :
ESR ≤
VP-P
ILOAD(MAX)
where LIR is the ratio of the peak to peak ripple current to
the average inductor current.
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RT8205A/B/C
In non-CPU applications, the output capacitor's size
depends on how much ESR is needed to maintain an
acceptable level of output voltage ripple :
VP-P
ESR ≤
LIR × ILOAD(MAX)
where VP-P is the peak-to-peak output voltage ripple.
Organic semiconductor capacitor(s) or specialty polymer
capacitor(s) are recommended.
For low input-to-output voltage differentials (VIN / VOUTx
< 2), additional output capacitance is required to maintain
stability and good efficiency in ultrasonic mode.
The amount of overshoot due to stored inductor energy
can be calculated as :
VSOAR ≤
(IPEAK )2 × L
2 × COUT × VOUTx
where IPEAK is the peak inductor current.
TM
TM
Although Mach Response DRV dual ramp valley mode
provides many advantages such as ease-of-use, minimum
external component configuration, and extremely short
response time, due to not employing an error amplifier in
the loop, a sufficient feedback signal needs to be provided
by an external circuit to reduce the jitter level. The required
signal level is approximately 15mV at the comparing point.
This generates VRipple = (VOUT / 2) x 15mV at the output
node. The output capacitor ESR should meet this
requirement.
Output Capacitor Stability
Stability is determined by the value of the ESR zero relative
to the switching frequency. The point of instability is given
by the following equation :
fESR =
f
1
≤ SW
2 × π × ESR × COUT
4
Do not put high-value ceramic capacitors directly across
the outputs without taking precautions to ensure stability.
Large ceramic capacitors can have a high- ESR zero
frequency and cause erratic, unstable operation. However,
it is easy to add enough series resistance by placing the
capacitors a couple of inches downstream from the
inductor and connecting VOUTx or the FBx divider close
to the inductor.
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DS8205A/B/C-06 July 2012
Unstable operation manifests itself in two related and
distinctly different ways: double-pulsing and feedback loop
instability.
Double-pulsing occurs due to noise on the output or
because the ESR is so low that there is not enough voltage
ramp in the output voltage signal. This “fools” the error
comparator into triggering a new cycle immediately after
the 300ns minimum off-time period has expired. Doublepulsing is more annoying than harmful, resulting in nothing
worse than increased output ripple. However, it may
indicate the possible presence of loop instability, which
is caused by insufficient ESR.
Loop instability can result in oscillations at the output
after line or load perturbations that can trip the overvoltage
protection latch or cause the output voltage to fall below
the tolerance limit.
The easiest method for checking stability is to apply a
very fast zero-to-max load transient and carefully observe
the output-voltage-ripple envelope for overshoot and ringing.
It helps to simultaneously monitor the inductor current
with an AC current probe. Do not allow more than one
cycle of ringing after the initial step-response under- or
overshoot.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum operation junction temperature. The maximum
power dissipation depends on the thermal resistance of
IC package, PCB layout, the rate of surroundings airflow
and temperature difference between junction to ambient.
The maximum power dissipation can be calculated by
following formula :
PD(MAX) = ( TJ(MAX) - TA ) / θJA
Where T J(MAX) is the maximum operation junction
temperature, TA is the ambient temperature and the θJA is
the junction to ambient thermal resistance.
For recommended operating conditions specification, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance θJA is layout dependent. For
WQFN-24L 4x4 packages, the thermal resistance θJA is
52°C/W on the standard JEDEC 51-7 four layers thermal
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RT8205A/B/C
test board. The maximum power dissipation at TA = 25°C
can be calculated by following formula :
PD(MAX) = (125°C − 25°C) / (52°C/W) = 1.923W for
WQFN-24L 4x4 packages
The maximum power dissipation depends on operating
ambient temperature for fixed T J(MAX) and thermal
resistance θJA. The Figure 7 of derating curves allows the
designer to see the effect of rising ambient temperature
on the maximum power allowed.
Maximum Power Dissipation (W)
2.0
Layout Considerations
Layout is very important in high frequency switching
converter design. If the IC is designed improperly, the PCB
could radiate excessive noise and contribute to the
converter instability. Certain points must be considered
before starting a layout using the RT8205A/B/C.
`
Place the filter capacitor close to the IC, within 12 mm
(0.5 inch) if possible.
`
Keep current limit setting network as close as possible
to the IC. Routing of the network should avoid coupling
to high-voltage switching node.
`
Connections from the drivers to the respective gate of
the high-side or the low-side MOSFET should be as
short as possible to reduce stray inductance. Use 0.65mm (25 mils) or wider trace.
`
All sensitive analog traces and components such as
VOUTx, FBx, GND, ENTRIPx, PGOOD, and TONSEL
should be placed away from high-voltage switching
nodes such as PHASEx, LGATEx, UGATEx, or BOOTx
nodes to avoid coupling. Use internal layer(s) as ground
plane(s) and shield the feedback trace from power traces
and components.
`
Gather ground terminal of VIN capacitor(s), VOUTx
capacitor(s), and source of low-side MOSFETs as close
as possible. PCB trace defined as PHASEx node, which
connects to source of high-side MOSFET, drain of lowside MOSFET and high-voltage side of the inductor,
should be as short and wide as possible.
Four Layers PCB
1.8
1.6
1.4
WQFN-24L 4x4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 7. Derating Curve of Maximum Power Dissipation
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RT8205A/B/C
Table 2. Operation Mode Truth Table
Mode
Condition
Power-UP VREGx < UVLO threshold
RUN
Over
Voltage
Protection
Under
Voltage
Protection
Comment
Transitions to discharge mode after a VIN POR and after REF
becomes valid. VREG5, VREG3, and REF remain active.
EN = high, VOUT1 or VOUT2
enabled
Normal Operation.
Either output > 111% of the nominal
level.
LGATEx is forced high. VREG3, VREG5 active. Exited by VIN
POR or by toggling EN, ENT RIPx
Either output < 70% of the nominal
level after 3ms time-out expires and
output is enabled
Either SMPS output is still high in
Discharge either standby mode or shutdown
mode
ENTRIPx < startup threshold,
Standby
EN = high.
Shutdown EN = low
Thermal
TJ > +150°C
Shutdown
EN
(V)
Low
ENTRIP1
(V)
X
“>1V”
=> High
Low
“>1V”
=> High
Low
“>1V”
=> High
High
(after ENTRIP2 is
high without 60us)
“>1V”
=> High
High
“>1V”
=> High
High
“>1V”
=> High
High
VREG3, VREG5 active.
All circuitry off.
All circuitry off. Exit by VIN POR or by toggling EN, ENTRIPx.
Table 3. Power-Up Sequencing
ENTRIP2
VREG5
VREG3
(V)
X
Off
Off
On
On
Low
(after REF
(after REF
powers up)
powers up)
On
On
High
(after REF
(after REF
powers up)
powers up)
On
On
High
(after REF
(after REF
powers up)
powers up)
On
On
Low
(after REF
(after REF
powers up)
powers up)
On
On
High (after ENTRIP1
(after REF
(after REF
is high without 60us)
powers up)
powers up)
On
On
High
(after REF
(after REF
powers up)
powers up)
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS8205A/B/C-06 July 2012
Both UGATEx and LGATEx are forced low and enter discharge
mode. VREG3, VREG5 active. Exited by VIN POR or by
toggling EN, ENTRIPx
During discharge mode, there is one path to discharge the
outputs capacitor residual charge. That is output capacitor
discharge to GND through an internal switch.
SMPS1
SMPS2
Off
Off
Off
Off
Off
On
On
(after
SMPS2 on)
On
On
Off
ON
On
(after
SMPS1 on)
On
On
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
27
RT8205A/B/C
Outline Dimension
D2
D
SEE DETAIL A
L
1
E
E2
e
b
A3
Symbol
2
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.700
0.800
0.028
0.031
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.180
0.300
0.007
0.012
D
3.950
4.050
0.156
0.159
D2
2.300
2.750
0.091
0.108
E
3.950
4.050
0.156
0.159
E2
2.300
2.750
0.091
0.108
e
L
1
2
DETAIL A
Pin #1 ID and Tie Bar Mark Options
A
A1
1
0.500
0.350
0.020
0.450
0.014
0.018
W-Type 24L QFN 4x4 Package
Richtek Technology Corporation
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot
assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be
accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
www.richtek.com
28
DS8205A/B/C-06 July 2012