RT8203
High-Efficiency, Quad Output, Main Power-Supply
Controllers for Notebook Computers
General Description
The RT8203 dual step-down, Switch Mode Power Supply
(SMPS) controllers generate logic-supply voltages in
battery-powered systems. The RT8203 include two pulse-
width modulation (PWM) controllers, adjustable from 2V
to 5.5V or fixed at 5V and 3.3V. These devices feature two
linear regulators providing 5V and 3.3V always-on outputs.
Each linear regulator provides up to 100mA output current
with automatic linear regulator bootstrapping to the main
SMPS outputs. The RT8203 include on-board power-up
sequencing, a power good (PGOOD) output, internal soft-
start, and soft-shutdown output discharge that prevents
negative voltages on shutdown.
Richtek's
proprietary Mach-
PWM
TM
“instant-on”
response, 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, which maximizes
efficiency in light-load applications, and fixed-frequency
PWM mode, which reduces RF interference in sensitive
applications. The RT8203 provides a pin-selectable
switching frequency, allowing either 200kHz/300kHz or
400kHz/500kHz operation of the 5V/3.3V SMPSs,
respectively. The RT8203 is available in SSOP-28 package.
Features
No Current Sense Resistor Needed
1.5% Output Voltage Accuracy
3.3V and 5V 100mA Bootstrapped Linear Regulators
Internal Soft-Start and Soft-Shutdown Output
Discharge
Mach-PWM with 100ns Load Step Response
3.3V and 5V Fixed or Adjustable Outputs
7V to 24V Input Voltage Range
Ultrasonic Mode Operation 25kHz (min.)
Power Good (PGOOD) Signal
Over Voltage Protection
Under Voltage Protection
Over Temperature Protection
RoHS Compliant and 100% Lead (Pb)-Free
Applications
Notebook and Subnotebook Computers
PDAs and Mobile Communication Devices
3- and 4-Cell Li+ Battery-Powered Devices
Pin Configurations
(TOP VIEW)
NC
PGOOD
ON3
ON5
ILIM3
EN
FB3
VREF
FB5
PRO
ILIM5
SKIP
TON
BOOT5
28
27
2
26
3
25
4
24
5
23
6
22
7
21
8
20
9
19
10
18
11
17
12
16
13
SSOP-28
15
14
BOOT3
PHASE3
UGATE3
LDO3
LGATE3
GND
VOUT3
VOUT5
VIN
LGATE5
LDO5
VCC
UGATE5
PHASE5
Ordering Information
RT8203
Package Type
A : SSOP-28
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Note :
Richtek 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.
SSOP-28
DS8203-05 April 2011
www.richtek.com
1
RT8203
Typical Application Circuit
5V
ALWAYS ON
C1
4.7µF
18
V
IN
7V to 24V
3
+
C2
1µF
R1
3.9
R2
47
17
5
11
LDO5
VCC
ILIM3
ILIM5
VIN
ON3
4
ON5
LDO3
RT8203
PRO
25
V
REF
V
CC
3.3V ALWAYS ON
C4
4.7µF
D2
BAT254
R4
V
CC
C3
1µF
C5
0.1µF
D1
C6
10µF
20
R6
10
1M
BAT254
R3
2.2
14
BOOT5
C8
0.1µF
16
UGATE5
15
EN
BOOT3
6
28
2.2
ON
OFF
C7
10µF
C9
0.1µF
Q2
AO4702
V
OUT5
5V
C10
L1
Q1
AO4702
UGATE3
26
PHASE3
LGATE3
27
L2
D4
Q4
BSC119N03
PHASE5
LGATE5
TON
V
OUT3
3.3V
C11
BSC119N03
D3
Q3
SEE
TABLE
19
13
24
21
VOUT5
8
VREF
VOUT3
22
SKIP
12
7
V
CC
R5
100k
C12
0.22µF
9
23
FB5
GND
FB3
1
NC
PGOOD
2
Power-Good
INDICATOR
Frequency-dependent Components
VOUT5
VOUT3
TON = VCC
f = 200kHz
L1 = 7.6μH
C10 = 330μF
TON = GND
f = 400kHz
L1 = 5.6μH
C10 = 150μF
TON = VCC
f = 300kHz
L2 = 4.7μH
C11 = 470μF
TON = GND
f = 500kHz
L2 = 3μH
C11 = 220μF
Figure 1. Fixed Voltage Regulator
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2
DS8203-05 April 2011
RT8203
5V
ALWAYS ON
C1
4.7µF
18
V
IN
7V to 24V
3
+
C2
1µF
R1
3.9
R2
47
17
5
11
LDO5
VCC
ILIM3
ILIM5
VIN
ON3
4
ON5
LDO3
RT8203
PRO
25
V
REF
V
CC
3.3V ALWAYS ON
C4
4.7µF
D2
BAT254
R4
V
CC
C3
1µF
C5
0.1µF
D1
C6
10µF
20
R6
10
1M
BAT254
R3
2.2
14
BOOT5
C8
0.1µF
16
UGATE5
15
EN
BOOT3
6
28
2.2
ON
OFF
C7
10µF
C9
0.1µF
Q2
AO4702
V
OUT5
5V
C10
L1
Q1
AO4702
UGATE3
26
PHASE3
LGATE3
27
L2
D4
Q4
BSC119N03
PHASE5
LGATE5
TON
V
OUT3
3.3V
C11
BSC119N03
D3
Q3
SEE
TABLE
R7
15k
R8
10k
19
13
24
21
VOUT5
VOUT3
22
7
12
R9
6.5k
V
CC
R5
100k
R10
10k
Power-Good
INDICATOR
C14
0.1µF
C13
0.1µF
9
FB3
FB5
C12
0.22µF
8
VREF
23
SKIP
1
NC
GND
PGOOD
2
Frequency-dependent Components
VOUT5
VOUT3
TON = VCC
f = 200kHz
L1 = 7.6μH
C10 = 330μF
TON = GND
f = 400kHz
L1 = 5.6μH
C10 = 150μF
TON = VCC
f = 300kHz
L2 = 4.7μH
C11 = 470μF
TON = GND
f = 500kHz
L2 = 3μH
C11 = 220μF
Figure 2. Adjustable Voltage Regulator
DS8203-05 April 2011
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3
RT8203
Functional Pin Description
Pin No.
1
2
Pin Name
NC
PGOOD
Connect to GND.
Power Good Open Drain Output. PGOOD is pulled low if either output is disable or is
more than 8.75% below its normal value.
VOUT3 Enable Input. The 3.3V SMPS is enable if ON3 is greater than the on level
3
ON3
and disable if ON3 is less than the off level. If ON3 is connected to V
REF
, the 3.3V
SMPS starts after the 5V SMPS reached regulation(delay start). Force ON3 below the
clear fault level to reset the fault latched.
VOUT5 Enable Input. The 5V SMPS is enable if ON5 is greater than the on level and
4
ON5
disable if ON5 is less than the off level. If ON5 is connected to VREF, the 5V SMPS
starts after the 3.3V SMPS reached regulation(delay start). Force ON5 below the clear
fault level to reset the fault latched.
VOUT3 Current Limit Adjustment. The GND-PHASE3 current limit threshold defaults
5
ILIM3
to 100mV if ILIM3 is tied to VCC. In adjustable mode, the current limit threshold is 1/10
the voltage seen at ILIM3 over 0.5V to 3V range. The logic threshold for switch over to
100mV default value is approximately VCC
−
1V.
Enable Control Input. The device enters its 15μA supply current shutdown mode if EN
is less than the EN input falling edge trip level and does not restart until EN is greater
6
EN
than the EN input rising edge trip level. Connect EN to VIN for automatically startup.
EN can be connected to VIN through a resistive voltage divider to implement a
programmable undervoltage lockout.
7
FB3
VOUT3 Feedback Input. Connect FB3 to GND for fixed 3.3V operation. Connect FB3
to a resistive voltage divider from VOUT3 to GND to adjust the output from 2V to 5.5V.
2V Reference Output. Bypass to GND with a 0.22μF
(MIN)
capacitor. VREF can source
8
VREF
up to 100μA for external loads. Loading VREF degrades FBx and VOUTx accuracy
according to the VREF load regulation error.
9
FB5
PRO
VOUT5 Feedback Input. Connect FB5 to GND for fixed 5V operation. Connect FB5 to
a resistive voltage divider from VOUT5 to GND to adjust the output from 2V to 5.5V.
Over Voltage and Under Voltage Fault Protection Enable/Disable. Connect PRO to
VCC to disable Over Voltage and Under Voltage protection. Connect PRO to GND to
enable Over Voltage and Under Voltage protection.
VOUT5 Current Limit Adjustment. The GND
−
PHASE5 current limit threshold defaults
11
ILIM5
to 100mV if ILIM5 is tied to VCC. In adjustable mode, the current limit threshold is 1/10
the voltage seen at ILIM5 over 0.5V to 3V range. The logic threshold for switch over to
100mV default value is approximately VCC
−
1V.
12
SKIP
Operation Mode Input Control. Connect SKIP to GND for diode-emulation mode
(DEM) or to VCC for CCM mode(fixed frequency). Connect to VREF or floating for
ultrasonic mode.
13
14
TON
BOOT5
Frequency Select Input. Connect to VCC for 200kHz/300kHz operation and to GND
for 400kHz/500kHz operation (VOUT5/VOUT3 switching frequency respectively).
Boost Capacitor Connection for 5V SMPS. Connect an external ceramic capacitor to
PHASE5 and an external diode to LDO5.
Pin Function
10
To be continued
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DS8203-05 April 2011
RT8203
Pin No.
15
16
17
Pin Name
PHASE5
UGATE5
VCC
Pin Function
Inductor Connection for 5V SMPS. PHASE5 is the internal lower supply rail for the
UGATE5 high side gate driver, and the current sense input for the 5V SMPS.
High Side N-MOSFET Floating Gate-Driver Output for VOUT5. Swings between
PHASE5 and BOOT5.
Analog Supply Voltage Input for the internal analog integrated circuit. Bypass to GND
with a 1μF ceramic capacitor.
5V Linear Regulator Output. LDO5 is the gate driver supply for the external
MOSFETs. LDO5 can provide a total of 100mA, including the MOSFET gate-driver
requirements and external loads. If VOUT5 is greater than the LDO5 switchover
threshold, the LDO5 regulator shuts down and LDO5 pin connects to VOUT5 through
a 1.4Ω switch. Bypass a 4.7μF ceramic capacitor to GND.
Low side N-MOSFET Gate-Drive Output for VOUT5. Swings between GND and
LDO5.
Power-Supply Input. VIN powers the LDO5/LDO3 linear regulators and is also used
for PWM control circuits. Connect VIN to the battery input or the AC adapter output.
VOUT5 Sense Input. Connect to the 5V output. VOUT5 is an input to the PWM control
circuit. It also serves as the 5V feedback input in fixed-voltage mode. If VOUT5 is
greater than the LDO5 switchover threshold, the LDO5 shuts down and LDO5
connects to VOUT5 through 1.4Ω switch.
VOUT3 Sense Input. Connect to the 3.3V output. VOUT3 is an input to the PWM
control circuit. It also serves as the 3.3V feedback input in fixed voltage mode. If
VOUT3 is greater than the LDO3 switchover threshold, the LDO3 shuts down and
LDO3 connects to VOUT3 through 1.5Ω switch.
Analog and Power Ground.
Low side N-MOSFET Gate-Drive Output for VOUT3. Swings between GND and
LDO5.
3.3V Linear Regulator Output. LDO3 can provide a total of 100mA to external loads. If
VOUT3 is greater than the LDO3 switchover threshold, the LDO3 regulator shuts
down and LDO3 pin connects to VOUT3 through a 1.5Ω switch. Bypass a 4.7μF
ceramic capacitor to GND.
High Side N-MOSFET Floating Gate-Driver Output for VOUT3. Swings between
PHASE3 and BOOT3.
Inductor Connection for 3.3V SMPS. PHASE3 is the internal lower supply rail for the
UGATE3 high side gate driver, and the current sense input for the 3.3V SMPS.
Boost Capacitor Connection for 3.3V SMPS. Connect an external ceramic capacitor to
PHASE3 and an external diode to LDO5.
18
LDO5
19
20
LGATE5
VIN
21
VOUT5
22
VOUT3
23
24
GND
LGATE3
25
LDO3
26
27
28
UGATE3
PHASE3
BOOT3
DS8203-05 April 2011
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5
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