RICHTEK RT8802A_12

®
RT8802A
2/3/4/5-Phase PWM Controller for High-Density Power Supply
General Description
Features
The RT8802A is a 2/3/4/5-phase synchronous buck controller
specifically designed to power Intel®/ AMD next generation
z
5V Power Supply
z
2/3/4/5-Phase Power Conversion with Automatic
Phase Selection
8-bit VID Interface, Supporting Intel VRD11/VRD10.x
and AMD K8, K8_M2 CPUs
VR_HOT and VR_FAN Indication
Precision Core Voltage Regulation
Power Stage Thermal Balance by DCR Current
Sensing
Adjustable Soft-start
Over Voltage Protection
Adjustable Frequency and Typical at 300kHz per
Phase
Power Good Indication
40-Lead VQFN Package
RoHS Compliant and 100% Lead (Pb)-Free
microprocessors. It implements an internal 8-bit DAC that is
identified by VID code of microprocessor directly. RT8802A
generates VID table that conform to Intel® VRD10.x and
VRD11 core power with 6.25mV increments and 0.5%
accuracy.
RT8802A adopts innovative time-sharing DCR current sensing
technique to sense phase currents for phase current balance,
load line setting and over current protection. Using a common
GM to sense all phase currents eliminates offset and linearity
variation between GMs in conventional current sensing
methods. As sub-milli-ohm-grade inductors are widely used
in modern motherboards, slight offset and linearity mismatch
will cause considerable current shift between phases. This
technique ensures good current balance in mass production.
Other features include over current protection, programmable
soft start, over voltage protection, and output offset setting.
RT8802A comes to a small footprint package with
VQFN-40L 6x6.
Ordering Information
z
z
z
z
z
z
z
z
z
z
Applications
z
z
z
Intel®/AMD New generation microprocessor for Desktop
PC and Motherboard
Low Output Voltage, High power density DC/DC
Converters
Voltage Regulator Modules
RT8802A
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.
VID7
VDD
VID6
VID5
VID3
VID4
VID2
VID1
(TOP VIEW)
VID0
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
Pin Configurations
VID_SEL
Package Type
QV : VQFN-40L 6x6 (V-Type)
40 39 38 37 36 35 34 33 32
VTT/EN
VR_Ready
FBRTN
FB
COMP
SS
QRSEL
VR_FAN
VR_HOT
TSEN
31
1
30
2
29
3
28
4
27
5
26
GND
6
25
7
24
8
23
41
9
22
10
21
PWM5
PWM4
PWM3
PWM2
PWM1
ISP1
ISP2
ISP3
ISP4
ISP5
ISN35
ISN24
IMAX
ISN1
ADJ
TCOC
RT
OFS
DVD
IOUT
11 12 13 14 15 16 17 18 19 20
VQFN-40L 6x6
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
DS8802A-09 March 2012
www.richtek.com
1
RT8802A
Marking Information
RT8802APQV
RT8802AZQV
RT8802APQV : Product Number
RT8802A
PQV
YMDNN
YMDNN : Date Code
RT8802AZQV : Product Number
RT8802A
ZQV
YMDNN
YMDNN : Date Code
RT8802AGQV
RT8802AGQV : Product Number
RT8802A
GQV
YMDNN
YMDNN : Date Code
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
www.richtek.com
2
DS8802A-09 March 2012
DS8802A-09 March 2012
GND
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
For AMD
PGOOD
VDDIO
VTT
VR_FAN
VR_HOT
VTT/EN
For Intel
R3
1.1k
OFS
FBRTN
Enable
VR_Ready
R4 R5 R6
10k10k10k
R12 0
R11
NC
R10
NC
R9
R13 NC
NC
C69
1 9 8 2 3 14 7 11 10
TSEN
IOUT
BTX_12V
C1
0.1uF
QRSEL
R2 10k
R1 10
GND
RT8802A
R20 0
R8
R42
BTX_5V
R21 100k
R22
470
100k
R23
470
R24
R25
100k
R26
470
0.1µF
C3
CPU_VSS
BTX_5V
BTX_5V
R7
9.52k
PWM3
PWM4
PWM5
ISN35
ISN24
ISN1
ISP1
ISP2
ISP3
ISP4
ISP5
28
29
30
20
19
18
25
24
23
22
21
R19
1.5k
R18 C8
15k 2.2nF
PWM2
PWM1
BTX_5V
VID7
For K8
IMAX
RT
ADJ
VID_SEL
VID0
VID1
VID2
VID3
VID4
VID5
VID6
VID7
VDD
DVD
TCOC
For K8_M2
40
39
38
37
36
35
34
33
32
31
12
C9
470pF
C7
5.6pF
15 13 17 16 6 5 4 26 27
COMP
SS
VID0
VID1
VID2
VID3
VID4
VID5
VID6
For Intel
For AMD
R14
C6
C5
56nF
FB
VDDIO
VID_SEL
BTX_5V
C4
R15
12k
R16
R17
R30
510
C10
1µF
R28
NC
BTX_5V
100
R32
510
C12
1µF
R29
NC
VCORE35
R31
510
C11
1µF
R27
CPU_VCC
R33
510
C13
1µF
VCORE1
VCORE24
C34
0.1µF
C22
C28
1N4148
VIN
PGND
6
3
NC
PGND
6
C29
C36
C39
1µF
IPS06N03LA
IPD09N03LA
4.7µF
C37
IPS06N03LA
IPD09N03LA
1200µF 4.7µF
C35
C32
1µF
4.7µF
C30
IPS06N03LA
IPD09N03LA
4.7µF
C24
IPS06N03LA
1200µF 4.7µF
1
BOOT
8
UGATE
7
4 VCC
PHASE
RT9619
2
5
VIN
LGATE
R40
10
NC
1N4148
VIN
PGND
6
C26
1µ
F
4.7µF
C17
IPD09N03LA
C23
C19
1µ
F
1200µF 4.7µF
1
BOOT
8
UGATE
7
4 VCC
PHASE
RT9619
2
5
VIN
LGATE
3
BTX_12V
C27
0.1µF
R38
10
BTX_12V
C21
0.1µF
1N4148
VIN
PGND
6
1
BOOT
3
8
NC
UGATE
7
4 VCC
PHASE
RT9619
2
5
VIN
LGATE
R36
10
BTX_12V
C14
0.1µF
1N4148
C16
1200µF 4.7µF
C15
VIN
1
BOOT
3
8
NC
UGATE
7
4 VCC
PHASE
RT9619
2
5
PWM
LGATE
R34
10
BTX_12V
BTX_12V
Q15
Q13
4.7µF
C38
Q11
Q9
4.7µF
C31
Q7
Q5
4.7µF
C25
Q3
Q1
C18
4.7µF
Q16
Q14
Q12
Q10
Q8
Q6
Q4
Q2
C40
3.3nF
R41
2.2
R39
2.2
C33
3.3nF
R37
2.2
C27
3.3nF
R35
2.2
C20
3.3nF
R43
VCC
RT2 4.3k
RT1 10k
NTC
L4
VCORE24
L3
VCORE35
L2
VCORE24
L1
NTC
C51 to C68
10µF x 18
C41 to C50
560µF x 10
VSS
VCORE1
RT8802A
Typical Application Circuit
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
www.richtek.com
3
RT8802A
Functional Pin Description
VTT/EN (Pin 1)
IOUT (Pin 11)
The pin is defined as the chip enable, and the VTT is
applied for internal VID pull high power and power sequence
monitoring.
Output current indication pin. The current through IOUT
pin is proportional to the total output current.
DVD (Pin 12)
VR_Ready (Pin 2)
Power good open-drain output.
Programmable power UVLO detection input. Trip threshold
is 1V at VDVD rising.
FBRTN (Pin 3)
RT (Pin 13)
Feedback return pin. VID DAC and error amplifier reference
for remote sensing of the output voltage.
The pin is defined to set internal switching operation
frequency. Connect this pin to GND with a resistor RRT to
set the frequency FSW.
FB (Pin 4)
Inverting input pin of the internal error amplifier.
FSW =
4.463 e 9
RRT + 3500
COMP (Pin 5)
Output pin of the error amplifier and input pin of the PWM
comparator.
OFS (Pin 14)
SS (Pin 6)
ADJ (Pin 15)
Connect this SS pin to GND with a capacitor to set the
soft-start time interval.
Current sense output for active droop adjusting. Connect
a resistor from this pin to GND to set the load droop.
QRSEL (Pin 7)
TCOC (Pin 16)
Quick response mode select pin. When QRSEL = GND
and quick response is triggered during heavy load to light
load transient, 2 channels will turn on simultaneously to
prevent VOUT undershoot. When QRSEL = NC and quick
response is triggered, all channels will turn on
simultaneously to prevent VOUT undershoot.
Input pin for setting thermally compensated over current
trigger point. Voltage on the pin is compared with VADJ. If
VADJ > VTCOC then OCP is triggered.
VR_FAN (Pin 8)
ISN1 (Pin 18)
The pin is defined to signal VR thermal information for
external VR thermal dissipation scheme triggering.
Current sense negative input pin for channel 1 current
sensing.
VR_HOT (Pin 9)
ISN24 (Pin 19)
The pin is defined to signal VR thermal information for
external VR thermal dissipation scheme triggering.
Current sense negative input pins for channel 2 and
channel 4 current sensing.
TSEN (Pin 10)
ISN35 (Pin 20)
Temperature detect pin for VR_HOT and VR_FAN.
Current sense negative input pins for channel 3 and
channel 5 current sensing.
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
The pin is defined for load line offset setting.
IMAX (Pin 17)
The pin is defined to set threshold of over current.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
www.richtek.com
4
DS8802A-09 March 2012
RT8802A
ISP1 (Pin 25), ISP2 (Pin 24), ISP3 (Pin 23),
ISP4 (Pin 22), ISP5 (Pin 21)
Current sense positive input pins for individual converter
channel current sensing.
PWM1 (Pin 26), PWM2 (Pin 27), PWM3 (Pin 28),
PWM4 (Pin 29), PWM5 (Pin 30)
PWM outputs for each driven channel. Connect these pins
to the PWM input of the MOSFET driver. For systems
which using 2/3/4 channels, pull PWM 3/4/5 pins up to
high.
VID7 (Pin 32), VID6 (Pin 33), VID5 (Pin 34), VID4 (Pin
35), VID3 (Pin 36), VID2 (Pin 37), VID1 (Pin 38),
VID0 (Pin 39), VID_SEL (40)
DAC voltage identification inputs for VRD10.x / VRD11 /
K8 / K8_M2. These pins are internally pulled up to VTT.
VIDSEL
VID [7]
Table
VTT
X
VR11
GND
X
VR10.x
VDD
NC
K8
VDD
GND
K8_M2
VDD (Pin 31)
GND [Exposed pad (41)]
IC power supply. Connect this pin to a 5V supply.
The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
Function Block Diagram
VDD
SS
VR_Ready
VTT/EN
DVD
Power On
Reset
Soft Start
& PGOOD
COMP
Oscillator
&
Ramp
Generator
RT
Pulse
Width
Modulator
& Output
Buffer
PWM1
PWM2
PWM3
PWM4
PWM5
FB
OFS
-
VID7
VID6
VID5
VID4
VID3
VID2
VID1
VID0
VID_SEL
+
DAC
EA
Clamp
+
Current
Processing
SUM/N
& OCP
Detection
IMAX
FBRTN
Mux
-
CSA
+
TSEN
VR_FAN
Temperature
Processing
VR_HOT
TCOC
Droop Tune
& Hi-I
Detection
Sample
& Hold
ADJ
GND
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
IOUT
Mux
ISN1
ISN24
ISN35
ISP1
Mux
ISP2
ISP3
ISP4
ISP5
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
DS8802A-09 March 2012
www.richtek.com
5
RT8802A
Table 1. Output Voltage Program (VRD10.x + VID6)
VID4
0
0
0
0
0
VID3
1
1
1
1
1
VID2
0
0
0
0
0
Pin Name
VID1
1
1
1
1
1
0
0
0
0
0
1
1
1
1
1
0
1
1
1
1
1
0
0
0
0
1
0
0
0
0
1
0
0
1
1
0
1
0
1
0
1.56875V
1.56250V
1.55625V
1.55000V
1.54375V
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
1
1
0
0
0
0
1
1
0
0
1
0
1
0
1
0
1.53750V
1.53125V
1.52500V
1.51875V
1.51250V
1.50625V
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
1
1
1
1
1
1
0
0
1
1
1
0
1
0
1
0
1.50000V
1.49375V
1.48750V
1.48125V
1.47500V
1.46875V
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1.46250V
1.45625V
1.45000V
1.44375V
1.43750V
1.43125V
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
0
0
0
1
1
0
0
1
1
0
1
0
1
1.42500V
1.41875V
1.41250V
1.40625V
1.40000V
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
0
0
1
1
1
1
0
1
0
0
1
1
0
0
1
0
1
0
1
1.39375V
1.38750V
1.38125V
1.37500V
1.36875V
1.36250V
VID0
0
0
1
1
1
VID5
1
1
0
0
1
VID6
1
0
1
0
1
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
Nominal Output Voltage DACOUT
1.60000V
1.59375V
1.58750V
1.58125V
1.57500V
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
www.richtek.com
6
DS8802A-09 March 2012
RT8802A
Table 1. Output Voltage Program (VRD10.x + VID6)
Pin Name
Nominal Output Voltage DACOUT
VID4
1
1
1
1
1
1
1
1
VID3
0
0
0
0
0
0
0
0
VID2
1
1
1
1
1
1
1
1
VID1
0
0
0
0
0
0
0
1
VID0
0
0
0
1
1
1
1
0
VID5
0
1
1
0
0
1
1
0
VID6
0
1
0
1
0
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
0
1
1
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1.30625V
1.30000V
1.29375V
1.28750V
1.28125V
1.27500V
1.26875V
1.26250V
1.25625V
1.25000V
1.24375V
1.23750V
1.23125V
1.22500V
1
1
1
1
0
0
0
1
1
0
1
0
0
1
1.21875V
1.21250V
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
0
1
1
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1.20625V
1.20000V
1.19375V
1.18750V
1.18125V
1.17500V
1.16875V
1.16250V
1,15625V
1.15000V
1.14375V
1.13750V
1.13125V
1.12500V
1
1
1
0
1
1
0
1.11875V
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
1.35625V
1.35000V
1.34375V
1.33750V
1.33125V
1.32500V
1.31875V
1.31250V
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
DS8802A-09 March 2012
www.richtek.com
7
RT8802A
Table 1. Output Voltage Program (VRD10.x + VID6)
Pin Name
Nominal Output Voltage DACOUT
VID4
1
1
1
1
1
1
1
1
VID3
1
1
1
1
1
1
1
1
VID2
1
1
1
1
1
1
1
1
VID1
1
1
1
1
1
1
1
1
VID0
0
0
0
0
1
1
1
1
VID5
0
0
1
1
0
0
1
1
VID6
1
0
1
0
1
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1.08750V
1.08125V
1.07500V
1.06875V
1.06250V
1.05625V
1.05000V
1.04375V
1.03750V
1.03125V
1.02500V
1.01875V
1.01250V
1.00625V
0
0
0
0
0
0
1
1
1
1
1
1
1
0
1.00000V
0.99375V
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0.98750V
0.98125V
0.97500V
0.96875V
0.96250V
0.95625V
0.95000V
0.94375V
0.93750V
0.93125V
0.92500V
0.91875V
0.91250V
0.90625V
0
0
1
1
1
1
1
0.90000V
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
1.11250V
1.10625V
1.10000V
1.09375V
OFF
OFF
OFF
OFF
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
www.richtek.com
8
DS8802A-09 March 2012
RT8802A
Table 1. Output Voltage Program (VRD10.x + VID6)
Pin Name
Nominal Output Voltage DACOUT
VID4
VID3
VID2
VID1
VID0
VID5
VID6
0
0
1
1
1
1
0
0.89375V
0
1
0
0
0
0
1
0.88750V
0
1
0
0
0
0
0
0.88125V
0
1
0
0
0
1
1
0.87500V
0
1
0
0
0
1
0
0.86875V
0
1
0
0
1
0
1
0.86250V
0
1
0
0
1
0
0
0.85625V
0
1
0
0
1
1
1
0.85000V
0
1
0
0
1
1
0
0.84375V
0
1
0
1
0
0
1
0.83750V
0
1
0
1
0
0
0
0.83125V
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
DS8802A-09 March 2012
www.richtek.com
9
RT8802A
Table 2. Output Voltage Program (VRD11)
Pin Name
Nominal Output Voltage DACOUT
Pin Name
Nominal Output Voltage DACOUT
OFF
OFF
1.60000V
1.59375V
1.58750V
1.58125V
1.57500V
1.56875V
HEX
27
28
29
2A
2B
2C
2D
2E
08
09
0A
0B
0C
0D
0E
0F
10
11
12
13
14
15
1.56250V
1.55625V
1.55000V
1.54375V
1.53750V
1.53125V
1.52500V
1.51875V
1.51250V
1.50625V
1.50000V
1.49375V
1.48750V
1.48125V
2F
30
31
32
33
34
35
36
37
38
39
3A
3B
3C
1.31875V
1.31250V
1.30625V
1.30000V
1.29375V
1.28750V
1.28125V
1.27500V
1.26875V
1.26250V
1.25625V
1.25000V
1.24375V
1.23750V
16
17
1.47500V
1.46875V
3D
3E
1.23125V
1.22500V
18
19
1A
1B
1C
1D
1E
1F
20
21
22
23
24
25
1.46250V
1.45625V
1.45000V
1.44375V
1.43750V
1.43125V
1.42500V
1.41875V
1.41250V
1.40625V
1.40000V
1.39375V
1.38750V
1.38125V
3F
40
41
42
43
44
45
46
47
48
49
4A
4B
4C
1.21875V
1.21250V
1.20625V
1.20000V
1.19375V
1.18750V
1.18125V
1.17500V
1.16875V
1.16250V
1.15625V
1.15000V
1.14375V
1.13750V
26
1.37500V
4D
1.13125V
HEX
00
01
02
03
04
05
06
07
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
1.36875V
1.36250V
1.35625V
1.35000V
1.34375V
1.33750V
1.33125V
1.32500V
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
www.richtek.com
10
DS8802A-09 March 2012
RT8802A
Table 2. Output Voltage Program (VRD11)
Pin Name
Nominal Output Voltage DACOUT
Pin Name
Nominal Output Voltage DACOUT
1.12500V
1.11875V
1.11250V
1.10625V
1.10000V
1.09375V
1.08750V
1.08125V
HEX
75
76
77
78
79
7A
7B
7C
56
57
58
59
5A
5B
5C
5D
5E
5F
60
61
62
63
1.07500V
1.06875V
1.06250V
1.05625V
1.05000V
1.04375V
1.03750V
1.03125V
1.02500V
1.01875V
1.01250V
1.00625V
1.00000V
0.99375V
7D
7E
7F
80
81
82
83
84
85
86
87
88
89
8A
0.83125V
0.82500V
0.81875V
0.81250V
0.80625V
0.80000V
0.79375V
0.78750V
0.78125V
0.77500V
0.76875V
0.76250V
0.75625V
0.75000V
64
65
0.98750V
0.98125V
8B
8C
0.74375V
0.73750V
66
67
68
69
6A
6B
6C
6D
6E
6F
70
71
72
73
0.97500V
0.96875V
0.96250V
0.95625V
0.95000V
0.94375V
0.93750V
0.93125V
0.92500V
0.91875V
0.91250V
0.90625V
0.90000V
0.89375V
8D
8E
8F
90
91
92
93
94
95
96
97
98
99
9A
0.73125V
0.72500V
0.71875V
0.71250V
0.70625V
0.70000V
0.69375V
0.68750V
0.68125V
0.67500V
0.66875V
0.66250V
0.65625V
0.65000V
74
0.88750V
9B
0.64375V
HEX
4E
4F
50
51
52
53
54
55
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
0.88125V
0.87500V
0.86875V
0.86250V
0.85625V
0.85000V
0.84375V
0.83750V
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
DS8802A-09 March 2012
www.richtek.com
11
RT8802A
Table 2. Output Voltage Program (VRD11)
Pin Name
HEX
9C
9D
9E
9F
A0
A1
A2
A3
Nominal Output Voltage DACOUT
Pin Name
Nominal Output Voltage DACOUT
0.63750V
0.63125V
0.62500V
0.61875V
0.61250V
0.60625V
0.60000V
0.59375V
HEX
C3
C4
C5
C6
C7
C8
C9
CA
A4
A5
A6
A7
A8
A9
AA
AB
AC
AD
AE
AF
B0
B1
0.58750V
0.58125V
0.57500V
0.56875V
0.56250V
0.55625V
0.55000V
0.54375V
0.53750V
0.53125V
0.52500V
0.51875V
0.51250V
0.50625V
CB
CC
CD
CE
CF
D0
D1
D2
D3
D4
D5
D6
D7
D8
X
X
X
X
X
X
X
X
X
X
X
X
X
X
B2
B3
0.50000V
X
D9
DA
X
X
B4
B5
B6
B7
B8
B9
BA
BB
BC
BD
BE
BF
C0
C1
X
X
X
X
X
X
X
X
X
X
X
X
X
X
DB
DC
DD
DE
DF
E0
E1
E2
E3
E4
E5
E6
E7
E8
X
X
X
X
X
X
X
X
X
X
X
X
X
X
C2
X
E9
X
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
X
X
X
X
X
X
X
X
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
www.richtek.com
12
DS8802A-09 March 2012
RT8802A
Table 2. Output Voltage Program (VRD11)
Pin Name
Nominal Output Voltage DACOUT
HEX
EA
X
EB
X
EC
X
ED
X
EE
X
EF
X
F0
X
F1
X
F2
X
F3
X
F4
X
F5
X
F6
X
F7
X
F8
X
F9
X
FA
X
FB
X
FC
X
FD
X
FE
OFF
FF
OFF
Note: (1) 0 : Connected to GND
(2) 1 : Open
(3) X : Don't Care
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
DS8802A-09 March 2012
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13
RT8802A
Table 3. Output Voltage Program (K8)
VID4
VID3
VID2
VID1
VID0
Nominal Output Voltage DACOUT
0
0
0
0
0
1.550
0
0
0
0
1
1.525
0
0
0
1
0
1.500
0
0
0
1
1
1.475
0
0
1
0
0
1.450
0
0
1
0
1
1.425
0
0
1
1
0
1.400
0
0
1
1
1
1.375
0
1
0
0
0
1.350
0
1
0
0
1
1.325
0
1
0
1
0
1.200
0
1
0
1
1
1.275
0
1
1
0
0
1.250
0
1
1
0
1
1.225
0
1
1
1
0
1.200
0
1
1
1
1
1.175
1
0
0
0
0
1.150
1
0
0
0
1
1.125
1
0
0
1
0
1.100
1
0
0
1
1
1.075
1
0
1
0
0
1.050
1
0
1
0
1
1.025
1
0
1
1
0
1.000
1
0
1
1
1
0.975
1
1
0
0
0
0.950
1
1
0
0
1
0.925
1
1
0
1
0
0.900
1
1
0
1
1
0.875
1
1
1
0
0
0.850
1
1
1
0
1
0.825
1
1
1
1
0
0.800
1
1
1
1
1
Shutdown
Note: (1) 0 : Connected to GND
(2) 1 : Open
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
www.richtek.com
14
DS8802A-09 March 2012
RT8802A
Table 4. Output Voltage Program (K8_M2)
Pin Name
Nominal Output Voltage DACOUT
VID5
VID4
VID3
VID2
VID1
VID0
0
0
0
0
0
0
1.5500
0
0
0
0
0
1
1.5250
0
0
0
0
1
0
1.5000
0
0
0
0
1
1
1.4750
0
0
0
1
0
0
1.4500
0
0
0
1
0
1
1.4250
0
0
0
1
1
0
1.4000
0
0
0
1
1
1
1.3750
0
0
1
0
0
0
1.3500
0
0
1
0
0
1
1.3250
0
0
1
0
1
0
1.3000
0
0
1
0
1
1
1.2750
0
0
1
1
0
0
1.2500
0
0
1
1
0
1
1.2250
0
0
1
1
1
0
1.2000
0
0
1
1
1
1
1.1750
0
1
0
0
0
0
1.1500
0
1
0
0
0
1
1.1250
0
1
0
0
1
0
1.1000
0
1
0
0
1
1
1.0750
0
1
0
1
0
0
1.0500
0
1
0
1
0
1
1.0250
0
1
0
1
1
0
1.0000
0
1
0
1
1
1
0.9750
0
1
1
0
0
0
0.9500
0
1
1
0
0
1
0.9250
0
1
1
0
1
0
0.9000
0
1
1
0
1
1
0.8750
0
1
1
1
0
0
0.8500
0
1
1
1
0
1
0.8250
0
1
1
1
1
0
0.8000
0
1
1
1
1
1
0.7750
1
0
0
0
0
0
0.7625
1
0
0
0
0
1
0.7500
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
DS8802A-09 March 2012
www.richtek.com
15
RT8802A
Table 4. Output Voltage Program (K8_M2)
Pin Name
Nominal Output Voltage DACOUT
VID5
VID4
VID3
VID2
VID1
VID0
1
0
0
0
1
0
0.7375
1
0
0
0
1
1
0.7250
1
0
0
1
0
0
0.7125
1
0
0
1
0
1
0.7000
1
0
0
1
1
0
0.6875
1
0
0
1
1
1
0.6750
1
0
1
0
0
0
0.6625
1
0
1
0
0
1
0.6500
1
0
1
0
1
0
0.6375
1
0
1
0
1
1
0.6250
1
0
1
1
0
0
0.6125
1
0
1
1
0
1
0.6000
1
0
1
1
1
0
0.5875
1
0
1
1
1
1
0.5750
1
1
0
0
0
0
0.5625
1
1
0
0
0
1
0.5500
1
1
0
0
1
0
0.5375
1
1
0
0
1
1
0.5250
1
1
0
1
0
0
0.5125
1
1
0
1
0
1
0.5000
1
1
0
1
1
0
0.4875
1
1
0
1
1
1
0.4750
1
1
1
0
0
0
0.4625
1
1
1
0
0
1
0.4500
1
1
1
0
1
0
0.4375
1
1
1
0
1
1
0.4250
1
1
1
1
0
0
0.4125
1
1
1
1
0
1
0.4000
1
1
1
1
1
0
0.3875
1
1
1
1
1
1
0.3750
Note: (1) 0 : Connected to GND
(2) 1 : Open
(3) The voltage above are load independent for desktop and server platforms. For mobile platforms the voltage above
correspond to zero load current.
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
www.richtek.com
16
DS8802A-09 March 2012
RT8802A
Absolute Maximum Ratings
z
z
z
z
z
z
z
z
(Note 1)
Supply Voltage, VDD -------------------------------------------------------------------------------------- 7V
Input, Output or I/O Voltage ------------------------------------------------------------------------------ (GND − 0.3V) to (VDD + 0.3V)
Power Dissipation, PD @ TA = 25°C
VQFN−40L 6x6 ---------------------------------------------------------------------------------------------- 2.857W
Package Thermal Resistance (Note 2)
VQFN-40L 6x6, θJA ----------------------------------------------------------------------------------------- 35°C/W
Junction Temperature -------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------- 260°C
Storage Temperature Range ----------------------------------------------------------------------------- −65°C to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) ------------------------------------------------------------------------------- 2kV
MM (Machine Mode) --------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
z
z
z
(Note 4)
Supply Voltage, VDD -------------------------------------------------------------------------------------- 5V ± 10%
Junction Temperature Range ----------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range ----------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VDD = 5V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
--
12
16
mA
Supply Current
VDD Nominal Supply Current
IDD
PWM 1, 2, 3, 4, 5 Open
VID Change Current
ISS
VR_RDY = High
0.5
1
1.5
mA
POR Threshold
VDDRTH
VDD Rising
4.0
4.2
4.5
V
Hysteresis
VDDHYS
0.2
0.5
--
V
0.9
1.0
1.1
V
--
60
--
mV
0.75
0.85
0.95
--
0.1
--
180
200
220
kHz
50
--
400
kHz
--
1.9
--
V
0.7
1.0
--
V
Power On Reset
VDVD Threshold
VTT Threshold
Trip (Low to High)
VDVDTH
Hysteresis
VDVDHYS
Trip (Low to High)
VTTTH
Hysteresis
VTTHYS
Enable
Enable
V
Oscillator
Free Running Frequency
f OSC
Frequency Adjustable Range
f OSC_ADJ
Ramp Amplitude
ΔVOSC
Ramp Valley
VRV
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
RRT = 20kΩ
RRT = 20kΩ
is a registered trademark of Richtek Technology Corporation.
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DS8802A-09 March 2012
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17
RT8802A
Parameter
Maximum On-Time of Each
Channel
RT Pin Voltage
Symbol
VRT
Test Conditions
Four Phase
Operation
RRT = 20kΩ
Min
Typ
Max
Unit
45
50
55
%
0.9
1.0
1.1
V
1
--
3
μs
−0.5
--
0.5
%
1V ≥ VDAC ≥ 0.8V
−5
--
5
mV
VDAC < 0.8V
−8
--
8
mV
Maximum On-Time
Reference and DAC
VDAC ≥ 1V
DACOUT Voltage Accuracy
ΔVDAC
DAC (VID0-VID125) Input Low
VILDAC
--
--
1/2VTT − 0.2
V
DAC (VID0-VID125) Input High
VIHDAC
1/2VTT + 0.2
--
--
V
12
15
18
kΩ
0.9
1.0
1.1
V
--
65
--
dB
--
10
--
MHz
--
8
--
V/μs
VID Pull-up Resistance
OFS Pin Voltage
VOFS
ROFS = 100kΩ
Error Amplifier
DC Gain
Gain-Bandwidth Product
GBW
Slew Rate
SR
Maximum Current
IEA_SLEW
50
--
--
μA
IISPFSS
100
--
--
μA
150
--
--
μA
COMP = 10pF
Current Sense GM Amplifier
CSN Full Scale Source Current
CSN Current for OCP
Input Offset Voltage
VOSCS
−5
0
5
mV
Protection
Over Voltage Trip
(FB-DACOUT)
Over Voltage Delay Time
ΔOVT
100
150
200
mV
--
20
--
μs
IMAX Voltage
VIMAX
RIMAX = 20kΩ
0.9
1.0
1.1
V
VPGOODL
IPGOOD = 4mA
--
--
0.2
V
VR_HOT Threshold Level
25
28
30
%VCC5
VR_HOT Hysteresis
--
5
--
%VCC5
Power Good
Output Low Voltage
Thermal Management
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.
Note 3. Devices are ESD sensitive. Handling precaution recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
www.richtek.com
18
DS8802A-09 March 2012
RT8802A
Typical Operating Characteristics
Frequency vs. RRT
GM
700
450
400
Positive Duty (ns)
Frequency (kHz)
600
500
400
300
200
350
300
250
PHASE 3
PHASE 1
PHASE 2
PHASE 4
PHASE 5
200
150
100
100
50
0
0
0
10
20
30
40
50
60
70
80
90
100
0
25
50
75
Output Voltage vs. Temperature
125
150
175
200
Frequency vs. Temperature
1.264
322
1.262
320
1.26
318
Frequency (kHz)1
Output Voltage (V)
100
ISN (μA)
(kΩ)
RRT (k
ٛ)
1.258
1.256
1.254
1.252
1.25
316
314
312
310
308
306
1.248
304
-20
0
20
40
60
80
100
-20
0
20
40
60
Temperature (°C)
Temperature (°C)
Power On from DVD
Power Off from DVD
DVD
(1V/Div)
DVD
(1V/Div)
SS
(1V/Div)
VOUT
(1V/Div)
SS
(1V/Div)
80
100
VOUT
(1V/Div)
PHASE 3
(10V/Div)
PHASE 3
(10V/Div)
Time (1ms/Div)
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
Time (1μs/Div)
is a registered trademark of Richtek Technology Corporation.
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19
RT8802A
Power On from VCC12
Power Off from VCC12
VCC12
(10V/Div)
SS
(1V/Div)
VCC12
(10V/Div)
SS
(1V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
PHASE 3
(10V/Div)
PHASE 3
(10V/Div)
Time (1ms/Div)
Time (1ms/Div)
Power On from VCC5
Power Off from VCC5
VCC5
(5V/Div)
SS
(1V/Div)
VCC5
(5V/Div)
SS
(1V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
PHASE 3
(10V/Div)
PHASE 3
(10V/Div)
Time (1ms/Div)
Time (25ms/Div)
Power On with OCP
Output Short Circuit
VR_Ready
(1V/Div)
VR_Ready
(1V/Div)
SS
(2V/Div)
SS
(2V/Div)
VOUT
1V/Div)
VOUT
(1V/Div)
PWM
(5V/Div)
PWM
(5V/Div)
Time (500μs/Div)
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
Time (1ms/Div)
is a registered trademark of Richtek Technology Corporation.
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20
DS8802A-09 March 2012
RT8802A
VOUT Overshoot
VOUT Droop
VOUT
(20mV/Div)
VOUT
(20mV/Div)
IOUT
(40A/Div)
IOUT
(40A/Div)
Time (2μs/Div)
Time (2μs/Div)
Dynamic VID
Dynamic VID
VOUT
(200mV/Div)
VOUT
(200mV/Div)
VID0
(500mV/Div)
VID0
(500mV/Div)
Time (50μs/Div)
Time (50μs/Div)
OVP
VR_Ready
(1V/Div)
SS
(2V/Div)
FB
(1V/Div)
PWM
(5V/Div)
Time (10μs/Div)
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
DS8802A-09 March 2012
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21
RT8802A
Applications Information
RT8802A is a multi-phase DC/DC controller specifically
designed to deliver high quality power for next generation
CPU. RT8802A controls a special power on sequence &
monitors the thermal condition of VR module to meet the
VRD11 requirement. Phase currents are sensed by
innovative time-sharing DCR current sensing technique
for channel current balance, droop tuning, and over current
protection. Using one common GM amplifier for current
sensing eliminates offset errors and linearity variation
between GMs. As sub-milli-ohm-grade inductors are
widely used in modern mother boards, slight mismatch
of GM amplifiers offset and linearity results in considerable
current shift between phases. The time-sharing DCR
current sensing technique is extremely important to
guarantee phase current balance in mass production.
MOSFETs. After VDD, VTT/EN, and DVD are ready,
RT8802A initiates its soft start cycle that is compliant
with Intel®VRD11 specification as shown in Figure 1. A
time variant internal current source charges the capacitor
connected to SS pin. SS voltage ramps up piecewise
linearly and locks VID_DAC output with a specified voltage
drop. Consequently, VCORE is built up according to
VID_DAC output and meet Intel® VRD11 requirement.
VR_READY output is pulled high by external resistor when
VCORE reaches VID_DAC output with 1~2ms delay. An
SS capacitor about 47nF is recommend for VRD11
compliance.
VDD POR, DVD, and VTT/EN ready
SS
VCORE
1.1V
Converter Initialization, Phase Selection, and
Power Good Function
The RT8802A initiates only after 3 pins are ready: VDD
pin power on reset (POR), VTT/EN pin enabled, and DVD
pin is higher than 1V. VDD POR is to make sure RT8802A
is powered by a voltage for normal work. The rising
threshold voltage of VDD POR is 4.2V typically. At VDD
POR, RT8802A checks PWM3, PWM4 and PWM5 status
to determine phase number of operation. Pull high PWM3
for two-phase operation; pull high PWM4 for three phase
operation; pull high PWM5 for four-phase operation. The
unused current sense pins should be connected to GND
or left floating.
VTT/EN acts as a chip enable pin and receives signal from
FSB or other power management IC.
DVD is to make sure that ATX12V is ready for drivers to
work normally. Connect a voltage divider from ATX12V to
DVD pin as shown in the Typical Application Circuit. Make
sure that DVD pin voltage is below its threshold voltage
before drivers are ready and above its threshold voltage
for minimum ATX12V during normal operation.
If any one of VDD, VTT/EN, and DVD is not ready, RT8802A
keeps its PWM outputs high impedance and the
companion drivers turn off both upper and lower
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
VR_Ready
VID on the fly
1~2ms
1~2ms
1~2ms
1~2ms
1~2ms
Figure 1. Timing Diagram During Soft Start Interval
Voltage Control
CPU VCORE voltage is Kelvin sensed by FB and FBRTN
pins and precisely regulated to VID_DAC output by internal
high gain Error Amplifier (EA). The sensed signal is also
used for power good and over voltage function. The typical
OVP trip point is 170mV above VID_DAC output. RT8802A
pulls PWM outputs low and latches up upon OVP trip to
prevent damaging the CPU. It can only restart by resetting
one of VDD, DVD, or VTT/EN pin.
RT8802A supports Intel VRD10.x, VRD11, AMD K8 and
AMD K8_M2 VID specification.
The change of VID_DAC output at VID on the fly is also
smoothed by capacitor connected to SS pin.
Consequently, Vcore shifts to its new position smoothly
as shown in Figure 2.
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22
DS8802A-09 March 2012
RT8802A
Consequently, the sensing current IX is proportional to
inductor current ILX and is expressed as :
I × DCRx
I X = LX
R CSNX
The sensed current IX is used for current balance and droop
tuning as described as followed. Since all phases share
one common GM, GM offset and linearity variation effect
is eliminated in practical applications. As sub-milli-ohmgrade inductors are widely used in modern mother boards,
slight mismatch of GM amplifiers offset and linearity results
in considerable current shift between phases. The time
sharing DCR current sensing technical is extremely
important to guarantee phase current balance in mass
production.
PWM4
V CORE
VID7
Figure 2. Vcore Response at VID on the Fly
DCR Current Sensing
RT8802A adopts an innovative time-sharing DCR current
sensing technique to sense the phase currents for phase
current balance (phase thermal balance) and load line
regulation as shown in Figure 3. Current sensing amplifier
GM samples and holds voltages VCx across the current
sensing capacitor Cx by turns in a switching cycle.
According to the Basic Circuit Theory, if
Lx = Rx × Cx then VCx = I × DCRx
LX
DCRx
Phase Current Balance
The sampled and held phase current IX are summed and
averaged to get the averaged current IX. Each phase current
IX then is compared with the averaged current. The
difference between IX and IX is injected to corresponding
PWM comparator. If phase current IX is smaller than the
averaged current , RT8802A increases the duty cycle of
corresponding phase to increase the phase current
accordingly and vice versa.
T1
T2
L1
DCR1
R1
C1
+ VC1 -
T3
T4
IX = ILX x DCRX/RCSNX
IX
S/H CKT
ISP1
+
CSA
-
T1
ISN1
T1
DCR3
R3
C3
+ VC3 -
L4
DCR4
R4
C4
+ VC4 -
RCSN1
ISP3
CSA: Current Sense Amplifier
L3
T3
ISN35
T3
ISP2
RCSN3
L2
DCR2
R2
C2
+ VC2 -
T2
T2 or T4
ISN24
ISP4
RCSN24
T4
Figure 3
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
All brandname or trademark belong to their owner respectively.
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23
RT8802A
IOFS
4
If
VCx =
RFB1
VCORE
+
COMP
EA
VADJ
4IX
+
-
DAC
LX
= (R X //RPX ) × Cx then
DCRx
RADJ
Figure 4. Load Line and Offset Function
RPX
× ILX × DCRx
Rx + RPX
With other phase kept unchanged, this phase would share
(RPX + Rx) / RPX times current than other phases. Figure 6
and 7 show different current ratio setting for the power
stage when Phase 4 is programmed 2 times current than
other phases. Figure 8 and 9 compare the above current
ratio setting results.
LX
VCORE = VDAC − VADJ +
RFB1
R OFS
Current Ratio Setting
Current ratio adjustment is possible as described below.
It is important for achieving thermal balance in practical
application where thermal conditions between phases are
not identical. Figure 5 shows the application circuit of GM
for current ratio requirement. According to Basic Circuit
Theory
RPX
Rx + RPX
VCx =
× ILX × DCRx
SRx × RPX × Cx
+1
Rx + RPX
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
Rx
+
VCx
-
Cx
RPX
+
To meet Intel® requirement of initial offset of load line,
RT8802A provides programmable initial offset function.
External resistor ROFS and voltage source at OFS pin
V
generate offset current IOFS = OFS
R OFS
, where VOFS is 1V typical. One quarter of IOFS flows
through RFB1 as shown in Figure 4. Error amplifier would
hold the inverting pin equal to VDAC - VADJ. Thus output
voltage is subtracted from VDAC - VADJ for a constant offset
voltage.
RFB1
VCORE = VDAC − VADJ −
4 × R OFS
A positive output voltage offset is possible by connecting
ROFS to VDD instead of to GND. Please note that when
ROFS is connected to VDD, VOFS is VDD − 2V typically and
half of IOFS flows through RFB1. VCORE is rewritten as :
ILX
DCRx
Output Voltage Offset Function
VOUT
T
Figure 5
IL4
1.5µH
1mΩ
3k
1µF
3k
Figure 6. GM4 Setting for current ratio function
IL1~3
1.5µH
1.5k
1mΩ
1µF
Figure 7. GM1~3 Setting for current ratio function
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DS8802A-09 March 2012
RT8802A
Current Ratio Function
35
Load Line without dead zone at light loads
1.31
IL4
30
1.3
20
V CORE (V)
I L (A)
w/o Dead Zone Compensation
RCSN open
1.29
25
IL3
IL2
IL1
15
1.28
1.27
1.26
10
RCSN2 = 82k
w/i Dead Zone Compensation
1.25
5
1.24
0
0
15
30
45
60
75
90
1.23
0
5
10
I OUT (A)
15
25
I OUT (A)
Figure 8
Figure 10
Current Balance Function
35
ILX
Lx
DCRx
Rx
Cx
30
25
I L (A)
20
VOUT
+ VCx -
20
IL3
+
IL2
-
15
GMx
10
Ix
IL1
5
RCSN
RCSN2
IL4
0
0
20
40
60
80
100
Figure 11. Application circuit of GM
120
I OUT (A)
Referring to Figure 11, IX is expressed as :
Figure 9
Dead Zone Elimination
RT8802A samples and holds inductor current at 50%
period by time-sharing sourcing a current IX to RCSN. At
light load condition when inductor current is not balance,
voltage VCx across the sensing capacitor would be
negative. It needs a negative IX to sense the voltage.
However, RT8802A CANNOT provide a negative IX and
consequently cannot sense negative inductor current. This
results in dead zone of load line performance as shown in
Figure 10. Therefore a technique as shown in Figure 11 is
required to eliminate the dead zone of load line at light
load condition.
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
IX =
ILX_50% × DCRx ILX_50% × DCRx
VOUT
+
+
R CSN2
R CSN2
R CSN
(1)
where ILX_50% is the of inductor current at 50% period. To
make sure RT8802A could sense the inductor current,
right hand side of Equation (1) should always be positive:
VOUT ILX_50% × DCRx ILX_50% × DCRx
+
+
≥0
RCSN2
RCSN2
RCSN
(2)
Since RCSN >> DCRx in practical application, Equation (2)
could be simplified as :
ILX_50% × DCRx
VOUT
≥
RCSN2
RCSN
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RT8802A
For example, assuming the negative inductor current is
ILX_50% = −5A at no load, then for
RCSN 330Ω, RADJ = 160Ω, VOUT = 1.300V
1.3V ≥ −5A × 1mΩ
RCSN2
330Ω
RCSN2 ≤ 85.8kΩ
If RADJ is connected as in Figure 14, RADJ = R1 + (R2//
R NTC), which is a negative temperature correlated
resistance. By properly selecting R1 and R2, the positive
temperature coefficient of DCR can be canceled by the
negative temperature coefficient of RADJ. Thus the load
line will be thermally compensated.
ADJ
Choose RCSN2 = 82kΩ
Figure 10 shows that dead zone of load line at light load
is eliminated by applying this technique.
R1
RADJ
RNTC
VR_HOT & VR_FAN Setting
VCC
5V
R2
Figure 14. RADJ Connection for Thermal Compensation
R1
TSEN
VTSEN
0.39 x VCC
+
CMP
-
Q1
+
CMP
-
Q2
Thermally compensated total current OCP
0.33 x VCC
+
CMP
-
Q3
VTCOC is compared with VADJ. If VADJ > VTCOC then OCP
is triggered.
RNTC
0.28 x VCC
Over Current Protection
ADJ
Figure 12
VTSEN
IMAX(1V)
VTSEN is inversely proportional
R1
TCOC
+
CMP
-
to Temperature.
R2
0.39 x VCC
0.33 x VCC
0.28 x VCC
Figure 15
Phase Current OCP
VR_FAN
VR_HOT
OC
Temperature
Figure 13. VR_HOT and VR_FAN Signal vs TSEN Voltage
Load Line Setting and Thermal Compensation
VADJ = Sum(IX) x RADJ = (DCR x RADJ / RCSN) x IOUT
= LL x IOUT
VOUT = VDAC − VADJ = VDAC − LL x IOUT
LL = DCR(PTC) x RADJ(NTC) / RCSN
DCR is the inductor DCR which is a PTC resistance.
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
RT8802A uses an external resistor RIMAX connected to
IMAX pin to generate a reference current IIMAX for over
current protection :
V
IIMAX = IMAX
RIMAX
where VIMAX is typical 1.0V. OCP comparator compares
each sensed phase current IX with this reference current
as shown in Figure 16. Equivalently, the maximum phase
current ILX(MAX) is calculated as below :
1
1I
X(MAX) = IIMAX
2
3
V
I X(MAX) = 3 IIMAX = 3 × IMAX
2 RIMAX
2
R
R
V
ILX(MAX) = I X × CSNX = 3 × IMAX × CSNX
RLX
2 RIMAX
DCR X
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DS8802A-09 March 2012
RT8802A
OCP Comparator
+
1/3 IX
-
1/2 IIMAX
EA Rising Slew Rate
VFB
Figure 16. Over Current Comparator
Phase current OCP and total current OCP with
thermal compensation
IX1
IOC, Phase
V-comparator
+
-
IX2
IOC, Phase
V-comparator
+
-
IX3
IOC, Phase
IX4
IOC, Phase
IX(n) ∝ IL(n)
CH1:(500mV/Div)
CH2:(2V/Div)
VCOMP
H Pulse width detector
H Last 20us? Y = 1, N = 0
V-comparator
+
V-comparator
+
-
Short circuit
protection
OCP
H Pulse width detector
H Last 20us? Y = 1, N = 0
Thermal compensated OCP
Reset while VID changing
Time (250ns/Div)
Figure 19. EA Falling Transient with 10pF Loading ;
Slew Rate = 8V/μs
Over current
protection
Figure 17
4.7k
B 4.7k
EA
+
A
Error Amplifier Characteristic
For fast response of converter to meet stringent output
current transient response, RT8802A provides large slew
rate capability and high gain-bandwidth performance.
VREF
Figure 20. Gain-Bandwidth Measurement by signal A
divided by signal B
EA Falling Slew Rate
Design Procedure Suggestion
a. Output filter pole and zero (Inductor, output capacitor
value & ESR).
VFB
b. Error amplifier compensation & saw-tooth wave
amplitude (compensation network).
c. Kelvin sense for VCORE.
VCOMP
CH1:(500mV/Div)
CH2:(2V/Div)
Time (250ns/Div)
Current Loop Setting
a. GM amplifier S/H current (current sense component
DCR, ISPX and ISNX pin external resistor value).
b. Over current protection trip point (RIMAX resistor).
Figure 18. EA Rising Transient with 10pF Loading ;
Slew Rate = 10V/μs
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27
RT8802A
VRM Load Line Setting
a. Droop amplitude (ADJ pin resistor).
b. No load offset (RCSN)
c. DAC offset voltage setting (OFS pin & compensation
network resistor).
d. Temperature coefficient compensation(TSEN external
resister & thermistor, resistor between ADJ and GND.)
Power Sequence & SS
DVD pin external resistor and SS pin capacitor.
PCB Layout
a. Kelvin sense for current sense GM amplifier input.
b. Refer to layout guide for other items.
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
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28
DS8802A-09 March 2012
RT8802A
Outline Dimension
D
SEE DETAIL A
D2
L
1
E
E2
e
b
A
1
1
2
2
DETAIL A
Pin #1 ID and Tie Bar Mark Options
A3
A1
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
0.800
1.000
0.031
0.039
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
5.950
6.050
0.234
0.238
D2
4.000
4.750
0.157
0.187
E
5.950
6.050
0.234
0.238
E2
4.000
4.750
0.157
0.187
e
L
0.500
0.350
0.020
0.450
0.014
0.018
V-Type 40L QFN 6x6 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.
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29