RichTek RT8800, RT8800B User Manual
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RT8800/B
General Purpose 2/3-Phase PWM Controller
for High-density Power Supply
General Description
The RT8800/B are general purpose multi-phase
synchronous buck controllers dedicating for high density
power supply regulation. The parts implement 2, and 3
buck switching stages operating in interleaved phase set
automatically. The output voltage is regulated and
controlled following the input voltage of FB pin. With such
a single analog control, the RT8800/B provide a simple,
flexible, wide-range and extreme cost-effective highdensity voltage regulation solutions for various high-density
power supply application. The RT8800/B multi-phase
architecture provide high output current while maintaining
low power dissipation on power devices and low stress
on input and output capacitors. The high equivalent
operating frequency also reduces the component
dimension a nd the output voltage ripple in load tra nsient.
RT8800/B implement both voltage and current loops to
achieve good regulation, response and power stage
thermal balance. The RT8800/B apply the time sharing
DCR current sensing technology newly a s well; with such
a topology, the RT8800/B extract the DCR of output
inductor as sense component to deliver a more precise
load line regulation and better thermal bala nce ca pability .
Moreover, the parts monitor the output voltage f or overcurrent and over-voltage protection; Soft-start and
programma ble under-voltage lockout are also provided to
a ssure the safety of power system.
Applications
Desktop CPU core power
Low Output Voltage, High power density DC-DC
Converters
V oltage Regulator Modules
Marking Information
For marking information, contact our sales re presentative
directly or through a RichTek distributor located in your
area, otherwise visit our website for detail.
Features
5V Power Supply Voltage
2/3-Phase Power Conversion with Automatic Phase
Selection (RT8800 : 2/3-Phase, RT8800B : 2-Pha se)
Output Voltage Controlled by External Reference
Voltage
Precise Core Voltage Regulation
Power Stage Thermal Balance by DCR Current
Sensing
Extreme Low-Cost, Lossless Time Sharing Current
Sensing
Internal Soft-start
Hiccup Mode Over-Current Protection
Over-Voltage Protection
Adjustable Operating Frequency and Typical at
300kHz Per Phase
Power Good indication
Small 16-Lead VQFN Package (For RT8800 only)
RoHS Compliant and 100% Lead (Pb)-Free
Ordering Information
RT8800/B
Package Type
QV : VQFN-16L 3x3 (Pb Free Only)
S : SOP-16
Operating Temperature Range
C : Commercial Standard
P : Pb Free with Commercial Standard
2-Phase
2/3-Phase
Note :
VQFN-16L 3x3 is in V-Type
RichTek Pb-free 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.
`100% matte tin (Sn) plating.
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1
RT8800/B
Pin Configurations
(TOP VIEW)
PWM3
GND
PI
PWM2
RT
PWM1
13141516
ISP1
12
ISP2
11
ISP3
10
PGOOD
9
8765
ICOM MON
DACFB
DACQ
FB
DVD
VDD
1
2
3
4
COMP
VQFN-16L 3x3
RT8800
Functional Pin Description
DACFB
Negative input of internal buffer amplifier for reference
voltage regulation. The pin voltage is locked at internal
V
= 0.8V by properly close the buffer a mplifier feedback
REF
loop.
DACQ
The pin is defined a s the output of internal buffer a mplifier
for reference voltage regulation.
FB
The pin is defined as the inverting input of internal error
amplif ier.
DVD
The pin is defined as a programmable power UVLO
detection input. T ri p threshold = 0.8V at V
DVD
rising.
VDD
DACFB
DACQ
FB
DVD
COMP
RT ICOMMON
2
3
4
5
6
7
PI
16
PWM2
15
PWM1
14
N/C
13
ISP1
12
ISP2
11
PGOOD
10
GND
98
SOP-16
RT8800B
ICOMMON
Common negative input of current sense a mplifiers for all
three channels.
PGOOD
Output power-good indication. The signal is implemented
a s a n output signal with open-drain type.
ISP1 , ISP2 , ISP3
Current sense positive inputs for individual converter
channel current sense.
PWM1 , PWM2 , PWM3
PWM outputs for ea ch pha se switching drive.
VDD
Chip power supply. Connect this pin to a 5V supply.
COMP
The pin is defined a s the output of the error a mplifier a nd
the input of all PWM comparators.
PI
The pin is defined a s the positive input of the error amplif ier.
RT
Switching frequency setting. Connect this pin to GND with
a resistor to set the frequency.
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2
GND
Chip power ground.
Exposed Pad (RT8800)
Exposed pad should be soldered to PCB board and
connected to GND.
DS8800/B-04 November 2005www.richtek.com
Typical Application Circuit
(Note : The inductor’ s DCR value must be large than 0.3mΩ
: X7R/R-type capacitor is required for all time constant setting capacitor of DCR sensing.)
CORE
Q1
R21
5
L2
0
12
UGATE1
PVCC
V
0.5uH
2.2
R25
Q2
PHB83N03LT
13
PHASE1
RT9602
PWM1
1
PHASE1
0
R22
4
C14
3.3nF
Q3
PHB95N03LT
LGATE1
PWM2
2
R23
C18 to C29
1000uF x 12
C16
1uF
C15
2200uF
Q4
0
7
8
9
UGATE2
PHASE2
L3
0.5uH
PHASE2
PHB83N03LT
LGATE2
C30 to C33
10uF x 4
R26
10
2.2
Q5
R24
C17
Q6
0
1uF
C10
3.3nF
PHB95N03LT
BOOT2
D2
SS12/SM
3
GND
PGND
6
D1
SS12/SM
L1
C13
1uH
12V
1000uF
C12
C9
1uF
11
1uF
C11
2200uF
BOOT1
VDD
14
RT8800/B
12V
C7
C8
R20
1uF
1uF
10
Optional for
5V
C1
R & C
33pF
C4
0
R16
15
1
4
6
C3
3k
R3
R2
C2
10nF
R1
15k
PWM1
VDD
FB
COMP
110k
R4
R17
DROOP
R
VID5
0
16
PWM2
PI
7
56k
R5
VID0
DACQ
3
27k
R6
VID1
10
GND
RT8800B
2
R11
1.8k
13k
R7
DACFB
VID2
ICOM M ON
Figure A. 2-phase with resistive DAC
12
ISP2
PGOOD
11
6.8k
R8
VID3
ISP1
DVD
10k
R12
3.3k
R9
RT
3.3V
VID4
PHASE2
R18
Optional
13
9
8
5
5.1k
R10
R
12V
C5
R13
1uF
R15
27k
16k
R14
3k
PHASE1
R19
Optional
R
430
R
Optional
C6
ICOMMON1
1uF
R
CORE
V
ICOMMON2
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3
RT8800/B
L1
0.5uH
CORE
R27
L2
2.2
V
0.5uH
L3
Q9
IN
V
0.5uH
C24 to C35
1000uF x 12
10uF x 4
C36 to C39
PHASE3
C23
3.3nF
Q7
Q8
PHASE2
Q3
3.3uF
C16
Q2
2.2
R19
R20
C15
1uF
0
12V
NC
3
20
21
1uF
C21
0
R25
14
15
LGATE3
LGATE2
12V
11
PVCC3
0
R26
10
PHASE3
UGATE3
PVCC2
GND
RT9605
PHASE2
D3
9
C22
BOOT3
1uF
12V
PHASE1
SB
5V
10
1uF
VDD
R23
C19
8
0
R22
LGATE1
PVCC1
C18
1uF
12V
PHASE1
Q6
3.3nF
C20
2.2
R24
1917
R21
UGATE1
1242223
PHASE2
R17
Optional
12
8
7
4
27k
R13
3.3V
5.1k
R10
C17
R
12V
0
1uF
C6
R15
1uF
R14
16k
3k
D2
PHASE1
R17
Optional
R
430
Q4 Q5
IN
V
12V
C7
1uF
ICOMMON1
R
Optional
ICOMMON2
R
CORE
V
12V
0
D1
C9
1uF
C8
1000uF
C14
C10 to C13
5V
C2
Optional
C1
33pF
R18
1uF
1500uF x 4
C4
4.7uF
R2
Q1
IN
V
1uH
UGATE2
BOOT2
PWM3
PWM2
PWM1
BOOT1
5
RT8800
DACQ
2
14
PWM2
R11
27k
4
10
GND
1.8k
13k
R7
2
PHASE3
R16
Optional
11
ISP3
ISP2
ICOMMON
DACFB
PGOOD
1
9
6.8k
R8
R
1uF
C5
ISP1
DVD
R12
3.3k
R9
RT
10k
7
16
15
PWM3
PWM1
13
16
VDD
3
FB
5
3k
COMP
R3
PI
6
C3
10nF
DROOP
R
R1
15k
56k
110k
R4R5R6
VID0
VID2
VID3
VID1
VID5
VID4
Figure B. 3-phase with re sistive DAC
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RT8800/B
CORE
C25 to C36
1000uF x 12
L1
0.5uH
PHASE3
Q7
C24
C37 to C40
3.3nF
10uF x 4
Q8
V
L2
0.5uH
2.2
R22
Q9
IN
V
L3
0.5uH
PHASE2
C16
3.3uF
2.2
R14
12V
9
C23
BOOT3
1uF
12V
PHASE1
SB
5V
10
1uF
VDD
R19
C20
8
0
R18
LGATE1
PVCC1
PHASE1
1uF
C19
12V
Q6
C21
3.3nF
Q5
2.2
R17
1uF
0
15
PVCC3
12V
11
PHASE3
GND
R21
10
UGATE3
C22
0
R20
14
Q3
Q2
R15
C17
1uF
12V
NC
3
0
20
21
LGATE3
LGATE2
PVCC2
RT9605
PHASE2
1917
R13
D1
C10
1uF
1000uF
C15
C11 to C14
5V
C3
Optional
C1
33pF
0
1uF
1500uF x 4
C5
R2
4.7uF
Q1
IN
V
1uH
C9
UGATE2
BOOT2
PWM3
PWM2
PWM1
BOOT1
5
RT8800
DACQ
2
4
14
PWM2
R4
2
R10
10
ISP3
ICOMMON
GND
DACFB
1
5.1k
PHASE3
Optional
11
ISP2
PGOOD
9
5.1k
R5
R
1uF
C6
ISP1
DVD
R6
7
16
15
PWM3
PWM1
13
16
VDD
3
FB
5
3k
COMP
R3
PI
6
C2
10nF
R1
15k
R
DROOP
RT
10k
UGATE1
12
8
7
4
3.3V
1242223
PHASE2
R11
Optional
27k
R7
R16
12V
C18
R
C7
0
1uF
R9
1uF
R8
16k
R12
3k
D2
PHASE1
R
Optional
430
8
VID3
Q4
IN
V
12V
C8
1uF
CORE
V
ICOMMON1
R
Optional
ICOMMON2
R
5
6
7
GND
VID4
VID0
C4
10nF
RT9401A/B
VID1
VID2
1
2
3
VDA
VDD
4
5V
Figure C. 3-phase with RT9401A/B DAC generator
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5
RT8800/B
Oscillator
&
Ramp Generator
+
+
+
+
+
+
Sample
& Hold
PWM1
PWM2
PWM3
OCP
SUM/N
& OCP
Detection
PGOOD
DVD
GND
Soft Start
+
+
-
ICOMMON
ISP1
ISP2
ISP3
PWM Logic
& Driver
PWMCP
+
-
PWM Logic
& Driver
PWMCP
+
-
PWM Logic
& Driver
PWMCP
+
-
+
+
+
Mux
Mux
Sample
& Hold
Sample
& Hold
VDD
FB
EA
GM
COMP
-
+
-
0.8V
V
REF
PI
Buffer
Amplifier
INH
INH
INH
Power On
Reset
RT
MAJ
500mV
OVP
DACFB
DACQ
Function Block Diagram
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RT8800/B
VID5 VID4 VID3 VID2 VID1 VID0 Nominal Output Voltage (V)
1 1 1 1 1 1 1.0800
1 1 1 1 1 0 1.1000
0 1 1 1 1 0 1.1125
1 1 1 1 0 1 1.1250
0 1 1 1 0 1 1.1375
1 1 1 1 0 0 1.1500
0 1 1 1 0 0 1.1625
1 1 1 0 1 1 1.1750
0 1 1 0 1 1 1.1875
1 1 1 0 1 0 1.2000
0 1 1 0 1 0 1.2125
1 1 1 0 0 1 1.2250
0 1 1 0 0 1 1.2375
1 1 1 0 0 0 1.2500
0 1 1 0 0 0 1.2625
1 1 0 1 1 1 1.2750
0 1 0 1 1 1 1.2875
1 1 0 1 1 0 1.3000
0 1 0 1 1 0 1.3125
1 1 0 1 0 1 1.3250
0 1 0 1 0 1 1.3375
1 1 0 1 0 0 1.3500
0 1 0 1 0 0 1.3625
1 1 0 0 1 1 1.3750
0 1 0 0 1 1 1.3875
1 1 0 0 1 0 1.4000
0 1 0 0 1 0 1.4125
1 1 0 0 0 1 1.4250
0 1 0 0 0 1 1.4375
1 1 0 0 0 0 1.4500
0 1 0 0 0 0 1.4625
1 0 1 1 1 1 1.4750
0 0 1 1 1 1 1.4875
1 0 1 1 1 0 1.5000
0 0 1 1 1 0 1.5125
1 0 1 1 0 1 1.5250
0 0 1 1 0 1 1.5375
1 0 1 1 0 0 1.5500
Table. Output Voltage Program
To be continued
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RT8800/B
VID5 VID4 VID3 VID2 VID1 VID0 Nominal Output Voltage (V)
0 0 1 1 0 0 1.5625
1 0 1 0 1 1 1.5750
0 0 1 0 1 1 1.5875
1 0 1 0 1 0 1.6000
1 0 1 0 0 1 1.6250
1 0 1 0 0 0 1.6500
1 0 0 1 1 1 1.6750
1 0 0 1 1 0 1.7000
1 0 0 1 0 1 1.7250
1 0 0 1 0 0 1.7500
1 0 0 0 1 1 1.7750
1 0 0 0 1 0 1.8000
1 0 0 0 0 1 1.8250
1 0 0 0 0 0 1.8500
Note: 1 : Open
or GND
0 : V
SS
Table. Output Voltage Program
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