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RT9911
6 Channel DC/DC Converters
General Description
Features
The RT9911 is a complete power-supply solution for digital
still cameras and other hand-held devices. It integrates
one selectable Boost/Buck DC/DC converter, one high
efficiency step-down DC/DC converter, one high efficiency
main step-up converter, one PWM converter for CCD
positive voltage, one inverter for CCD negative voltage and
one white LED driver for LCD backlight. The RT9911 is
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1.6V to 5.5V Battery Input Voltage Range
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Synchronous Boost/Buck Selectable DC/DC
Converter
` Internal Switches
` Up to 95% Efficiency
Syn-Buck DC/DC Converters
` 0.8V to 5.5V Adjustable Output Voltage
` Up to 95% Efficiency
` 100%(MAX) Duty Cycle
` Internal Switches
Main Boost DC/DC Converter
` Adjustable Output Voltage
` Up to 97% Efficiency
PWM Converter for CCD Positive Voltage
Inverter for CCD Negative Voltage
White LED Driver for LCD Panel Backlight
Up to 1.4MHz Adjustable Switching Frequency
1μ
μA Supply Current in Shutdown Mode
External Compensation Network for all Converters
Independent Enable Pin to Shutdown Each
Channel.
40-Lead VQFN Package
RoHS Compliant and 100% Lead (Pb)-Free
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targeted for applications that use either two or three primary
cells or a single lithium-ion battery.
RT9911 is available in VQFN-40L 6x6. Each DC-DC converter
has independent shutdown input.
Ordering Information
RT9911
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z
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Package Type
QV : VQFN-40L 6x6 (V-Type)
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Note :
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z
z
z
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Richtek products are :
`
`
RoHS compliant and compatible with the current require-
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ments of IPC/JEDEC J-STD-020.
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Suitable for use in SnPb or Pb-free soldering processes.
Pin Configurations
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PVDD2
COMP2
FB2
SELECT
EN1
EN2
EN3
EN5
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Digital Still Camera
PDA
Protable Device
EN6
z
EN4
(TOP VIEW)
Applications
40 39 38 37 36 35 34 33 32 31
GND
OK2
RT
VREF
VDDM
GND
FB1
COMP1
PGND1
LX1
1
30
2
29
3
28
4
27
5
26
GND
6
25
7
24
8
23
41
9
22
21
10
LX2
PGND2
FB3
COMP3
CS3
DRN3
DRP3
VFB6
CFB6
COMP6
PVDD3
EXT6
EXT4
FB4
COMP4
PVDD5
EXT5
FB5
PVDD1
COMP5
11 12 13 14 15 16 17 18 19 20
VQFN-40L 6x6
DS9911-05 April 2011
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1
RT9911
Typical Application Circuit
VBAT
VS
3.3V
VBAT
1.8V to 3.2V
I/O
3.3V
500mA
D9 11
C3 to C6
10µFx4
R2
470k
Q1
C7
100pF
PVDD1
10 LX1
7
FB1
9 PGND1
R3
150k
C8
0.1µF
R1
510k
34
SELECT
VS
3.3V
L1
4.7µH
C19
1µF
EXT4
RT9911
PVDD5
EXT5
2 OK2
1
GND
R4
300k
C10
100pF
33
R5 240k
31
C11
10µF
VBAT
GND
SS0520
3 R10
C15 to Q2
C18
10µFx4
EXT6
VBAT
25 DRN3
Q3
24
DRP3
28
FB3
COMP1
8
VFB6
CFB6
EN1
EN1
EN3
EN4
EN5
EN6
R8
2.2M
R9
205k
C29
10µF
R11
1M
CCD
-8V/40mA
C26 to C27
10µFx2
R12
125k
C28
4.7µF
R22
20k
L6
4.7µH
SS0520
D8
19
Q6
CS3
R7
90.9k
C25
100pF
13
6
C22
100pF
L5
3.3µH
Q5
PVDD3
COMP6
R6
100pF 470k
PVDD2
L3
4.7µH
26
C14
14
VREF 4
COMP5
C12 to C13
10µFx2
D5
C21
10µF
CCD
12V
20mA
VBAT
C23
C24
1µF
10µF
Bottom PAD
20
Motor
5V
500mA
FB2
COMP4
VS
3.3V
FB5
COMP3
C9
10µF
15
Q4
D7
30 LX2
COMP2
VCORE
1.8V
300mA
RT
D6
18
FB4 17
3.3V
29 PGND2
L2
4.7µH
L4
4.7µH
SS0520
5
VDDM
C1 to C2
10µFx2
C20
10µF
23
22
35
36
37
38
39
40
C30
4.7µF
R13
300k
D1
D2
D3
D4
EN1
EN2
EN3
EN4
EN5
EN6
R14
10
32 27 16 12 21
R15 to R21
1M
C31 to C36
Figure 1. Application Circuit for 2-Cells Battery Supply
Note :
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Bottom pad is GND pad, can be short to pin 6 (GND).
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Please remove Q2 when use Async Boost and remove D5 when use Sync Boost.
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DS9911-05 April 2011
RT9911
VBAT
3.4V to 4.2V
C22
1µF
C1 to C2
10µFx2
R1
470k
R2 150k
C10 to C11
10µFx2
L2
4.7uH
R4
470k
Q2
VDDM
SELECT
Bottom PAD
PVDD3
GND
EXT6
L5
3.3µH
Q5
SS0520
3 R12
C27
100pF
13
VBAT
25 DRN3
Q3
24
DRP3
28
FB3
COMP1
R9
90.9k
8
VFB6
CFB6
EN1
EN1
EN3
EN4
EN5
EN6
6
D8
19
23
22
35
36
37
38
39
40
C30
10µF
R13
1M
C28
10µF
R14
125k
C29
4.7µF
CCD
-8V
40mA
R24
20k
L6
4.7µH
SS0520
Q6
CS3
COMP5
C18
to C21
10µFx4
L3
4.7µH
26
14
VREF 4
9
PGND1
PGND2 29
COMP4
R8
470k
D5
R10
2.2M
C26
10µF
15
FB2
COMP3
C15 to C16
10µFx2
C25
100pF
R11 205k
D7
2 OK2
1
GND
VBAT
10pF
RT
FB5
20
C17
EXT5
COMP2
Motor
5V
500mA
PVDD2
C12
100pF
R5 226k
Q1
DDR
2.5V
250mA
FB1
30 LX2
33
R3
510k
C24
10µF
Q4
RT9911
PVDD5
31
2.5V
18
CCD
12V
20mA
VBAT
VBAT
C8 to C9
10µFx2
D6
FB4 17
C7
100pF
7
C13
0.1µF
EXT4
COMP6
C3 to C6
10µFx4
L4
4.7µH
SS0520
5
34
11
PVDD1
L1
4.7µH 10
LX1
I/O
3.3V
500mA
C23
10µF
VBAT
VBAT
C31
4.7µF
R15
300k
D1
D2
D3
D4
EN1
EN2
EN3
EN4
EN5
EN6
R16
10
32 27 16 12 21
R17 to R23
1M
C32 to C37
Figure 2. Application Circuit for Li-ion Battery Supply
Note :
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Bottom pad is GND pad, can be short to pin 6 (GND).
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Please remove Q2 when use Async Boost and remove D5 when use Sync Boost.
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Output voltage setting
CH1: 0.8Vx(1+R1/R2) ex: I/O 3.3V = 0.8x(1+470k/150k)
CH2: 0.8Vx(1+R4/R5) ex: DDR 2.5V = 0.8x(1+470k/226k)
CH3: 0.8Vx(1+R8/R9) ex: MOTOR 5V = 0.8x(1+470k/90.9k)
CH4: 1.0Vx(1+R10/R11) ex: CCD 12V = 1.0x(1+2.2M/205k)
CH5: -1.0Vx(R13/R14) ex: CCD -8V = -1.0x(1M/125k)
DS9911-05 April 2011
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RT9911
Functional Pin Description
Pin No. Pin Name
Pin Function
I/O
Internal State at
Shut Down
I/O Configuration
OK 2
1
GND
Analog Ground Pin
--
--
2
OK2
External Switch Control.
OUT
High Impedance
3
RT
OUT
Pull Low
5
VDDM
Device Input Power Pin
IN
--
6
GND
Analog Ground Pin
--
--
Frequency Setting Pin. Frequency
is 500kHz if RT pin not connected.
GND
VDDM
+
-
RT
GND
VDDM
1.0V
4
VREF
1.0V Reference Pin
OUT
High Impedance
+
-
VREF
7
FB1
8
COMP1
9
PGND1
10
Feedback Input Pin of CH1.
Feedback Compensation Pin of
IN
High Impedance
OUT
Pull Low
Power Ground Pin of CH1.
--
--
LX1
Switch Node of CH1.
OUT
High Impedance
11
PVDD1
Power Input Pin of CH1.
IN
--
12
COMP5
OUT
Pull Low
CH1.
Feedback Compensation Pin of
CH5.
0.8V
FB1
+
COMP1
-
PVDD1
LX1
PGND1
FB5
+
COMP5
-
13
FB5
Feedback Input Pin of CH5.
IN
High Impedance
14
EXT5
External Power Switch of CH5.
OUT
Pull High
PVDD5
15
PVDD5
16
COMP4
17
FB4
Power Input Pin of CH4, CH5 and
CH6.
Feedback Compensation Pin of
CH4.
Feedback Input Pin of CH4.
EXT5
IN
--
OUT
Pull Low
IN
1.0V
FB4
+
COMP4
-
High Impedance
To be continued
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DS9911-05 April 2011
RT9911
Pin No. Pin Name
Pin Function
I/O
Internal State at
I/O Configuration
Shut Down
PVDD5
18
EXT4
External Power Switch of CH4.
OUT
Pull Low
EXT4
PVDD5
19
EXT6
External Power Switch of CH6.
OUT
Pull Low
20
PVDD3
Power Input Pin of CH3.
IN
--
24
DRP3
External PMOS Switch Pin for CH3. OUT
21
COMP6
22
CFB6
Feedback Compensation Pin of
CH6.
Current Feedback Input Pin for
CH6.
EXT6
PVDD3
DRP3
Pull High
OUT
Pull Low
IN
High Impedance
0.2V
CFB6
+
-
COMP6
VFB6
1.0V
23
VFB6
Voltage Feedback Input Pin for
CH6.
IN
High Impedance
+
-
50uA
PVDD3
25
DRN3
External NMOS Switch Pin for CH3. OUT
Pull Low
DRN3
VDDM
26
CS3
Current Sense Input Pin for CH3
IN
High Impedance
CS3
To be continued
DS9911-05 April 2011
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RT9911
Pin No. Pin Name
27
COMP3
28
FB3
29
Pin Function
Feedback Compensation Pin of
I/O
Internal State at
Shut Down
OUT
Pull Low
Feedback Input Pin of CH3.
IN
High Impedance
PGND2
Power Ground Pin of CH2
--
--
30
LX2
Switch Node of CH2
OUT
High Impedance
31
PVDD2
Power Input Pin of CH2.
IN
--
32
COMP2
OUT
Pull Low
33
FB2
IN
High Impedance
CH3
Feedback Compensation Pin of
CH2.
Feedback Input Pin of CH2.
I/O Configuration
0.8V
FB3
COMP3
+
-
PVDD2
LX2
PGND2
0.8V
FB2
+
-
COMP2
VDDM
CH1 Boost/Buck Selection Pin.
34
SELECT
Logic state can’t be changed during IN
Pull Low
SELECT
operation.
2uA
VDDM
35
EN1
Enable Input Pin of CH1.
IN
Pull Low
EN1
2uA
VDDM
36
EN2
Enable Input Pin of CH2.
IN
Pull Low
EN2
2uA
To be continued
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DS9911-05 April 2011
RT9911
Pin No. Pin Name
Pin Function
I/O
Internal State at
Shut Down
I/O Configuration
VDDM
37
EN3
Enable Input Pin of CH3.
IN
EN3
Pull Low
2uA
VDDM
38
EN4
Enable Input Pin of CH4.
IN
EN4
Pull Low
2uA
VDDM
39
EN5
Enable Input Pin of CH5.
IN
EN5
Pull Low
2uA
VDDM
40
EN6
Enable Input Pin of CH6.
IN
EN6
Pull Low
2uA
The exposed pad must be soldered
Exposed
Pad (41)
GND
to a large PCB and connected to
GND for maximum power
--
--
--
dissipation.
DS9911-05 April 2011
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RT9911
Function Block Diagram
VDDM
EN4
PVDD5
EXT4
COMP4
FB4
CH4
V-Mode
Step-Up
PWM
-
SELECT
EN1
PVDD1
CH1
C-Mode
Step-Up or
Step-Down
LX1
+
PGND1
COMP1
1.0V
REF
EN5
-
PVDD5
+
0.8V
REF
CH5
Inverter
EXT5
COMP5
FB5
FB1
EN2
PVDD2
+
CH2
C-Mode
Step-Down
1.0V
REF
VREF
LX2
PGND2
COMP2
FB2
OK2
Switch
Controller
+
0.8V
REF
EN6
EN3
PVDD3
PVDD5
CH6
WLED
EXT6
VFB6
-
DRP3
CH3
C-Mode
Step-Up
PVDD3
+
DRN3
1.0V
REF
50uA
CS3
COMP6
-
CFB6
+
Oscillator
Thermal
Shutdown
RT
GND
+
0.2V
REF
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8
COMP3
FB3
0.8V
REF
DS9911-05 April 2011
RT9911
Absolute Maximum Ratings
z
z
z
z
z
z
z
z
z
(Note 1)
Supply Voltage, VDDM ----------------------------------------------------------------------------------------- −0.3V to 7V
Power Switch ---------------------------------------------------------------------------------------------------- −0.3V to (VDD + 0.3V)
The Other Pins -------------------------------------------------------------------------------------------------- −0.3V to 7V
Power Dissipation, PD @ TA = 25°C
VQFN−40L 6x6 -------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
VQFN-40L 6x6, θJA --------------------------------------------------------------------------------------------Junction Temperature -----------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------Storage Temperature Range --------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Mode) ----------------------------------------------------------------------------------MM (Machine Mode) -------------------------------------------------------------------------------------------
Recommended Operating Conditions
z
z
z
z
2.778W
36°C/W
150°C
260°C
−65°C to 150°C
2kV
200V
(Note 4)
Dimming Control Frequency Range, CH6 ---------------------------------------------------------------- 300Hz to 900Hz
Supply Voltage, VDDM ----------------------------------------------------------------------------------------- 2.4V to 5.5V
Junction Temperature Range --------------------------------------------------------------------------------- −40°C to 125°C
Operation Temperature Range ------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VDDM = 3.3V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
--
--
1.6
V
2.4
5.9
-6.5
5.5
--
V
V
EN1 = EN2 = EN3 = EN4 = EN5
= EN6 = 0V
--
1
10
μA
VDDM = 3.3V, Non-Switching
--
--
430
μA
VDDM = 3.3V, Non-Switching
--
--
350
μA
I Q3
VDDM = 3.3V, Non-Switching
--
--
350
μA
I Q4
VDDM = 3.3V, Non-Switching
--
--
300
μA
I Q5
VDDM = 3.3V, Non-Switching
--
--
300
μA
I Q6
VDDM = 3.3V, Non-Switching
--
--
350
μA
Supply Voltage
VDDM Minimum Startup Voltage
VST
(Note 5)
VDDM Operating Voltage
VDDM Over Voltage Protection
VDDM
VDDM Pin Voltage
Supply Current
Shutdown Supply Current into VDDM I OFF
CH1 (Sync-Boost or Syn-Buck)
I Q1
Supply Current into VDDM
CH2 (Sync-Buck) Supply Current into
I Q2
VDDM
CH3 (Sync-Boost) Supply Current
into VDDM
CH4 (Asyn-Boost) Supply Current
into VDDM
CH5 (Asyn-Inverter) Supply Current
into VDDM
CH6 (Asyn-Boost) Supply Current
into VDDM
To be continued
DS9911-05 April 2011
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RT9911
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Oscillator
Operation Frequency
CH1 Maximum Duty Cycle (Boost)
f OSC
DMAX1
RT Open
SELECT = 3.3V, VFB1 = 0.7V
450
80
550
85
650
90
kHz
%
CH1 Maximum Duty Cycle (Buck)
CH2 Maximum Duty Cycle
DMAX1
DMAX2
SELECT = 0V, VFB1 = 0.7V
VFB2 = 0.7V
100
100
---
---
%
%
CH3 Maximum Duty Cycle
DMAX3
VFB3 = 0.7V
75
80
90
%
CH4 Maximum Duty Cycle
CH5 Maximum Duty Cycle
DMAX4
DMAX5
VFB4 = 0.9V
VFB5 = 0.1V
90
94
98
%
CH6 Maximum Duty Cycle
DMAX6
VCFB6 = 0.18V, VFB6 = 0.9V
0.788
0.8
0.812
V
0.98
1
1.02
V
−15
--
-1
+15
--
mV
V
0.18
0.2
0.22
V
0.984
1
1.016
V
--
--
10
mV
--
0.2
--
ms
--
22
--
μA
--
22
--
μA
RDS(ON)P1 P-MOSFET, PVDD1 = 3.3V
--
200
300
mΩ
RDS(ON)N1 N-MOSFET, PVDD1 = 3.3V
--
200
300
mΩ
1.3
2
4
A
SELECT=1
RDS(ON)P2 P-MOSFET, PVDD2 = 3.3V
2
--
2.5
300
4
450
A
mΩ
RDS(ON)N2 N-MOSFET, PVDD2 = 3.3V
--
300
450
mΩ
1.3
2
4
A
RDS(ON)NP3 P-MOSFET, PVDD3 = 3.3V
--
6
15
Ω
RDS(ON)NN3 N-MOSFET, PVDD3 = 3.3V
--
6
15
Ω
RDS(ON)PP3 P-MOSFET, PVDD3 = 3.3V
--
6
15
Ω
RDS(ON)PN3 N-MOSFET, PVDD3 = 3.3V
--
6
15
Ω
RDS(ON)P4 P-MOSFET, PVDD3 = 3.3V
--
6
15
Ω
RDS(ON)N4 N-MOSFET, PVDD3 = 3.3V
--
6
15
Ω
Feedback Regulation Voltage
Feedback Regulation Voltage @ FB1,
FB2, FB3
VFB1, 2,3
Feedback Regulation Voltage @FB4
VFB4
Feedback Regulation Voltage @ FB5 VFB5
Feedback Regulation Voltage @ VFB6 VVFB6
Feedback Regulation Voltage @ CFB6 VCFB6
Reference
VREF Output Voltage
VREF Load Regulation
VREF
0μA < I REF < 100μA
Error Amplifier
GM (CH1, CH2, CH3, CH4, CH5, CH6)
Compensation Source Current (CH1,
CH2, CH3, CH4, CH5, CH6)
Compensation Sink Current (CH1, CH2,
CH3, CH4, CH5, CH6)
Power Switch
CH1 On Resistance of MOSFET
CH1 Switch Current Limitation (Buck)
CH1 Switch Current Limitation (Boost)
CH2 On Resistance of MOSFET
SELECT=0
CH2 Switch Current Limitation
CH3 On Resistance of DRN3
CH3 On Resistance of DRP3
CH4 On Resistance of MOSFET
To be continued
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DS9911-05 April 2011
RT9911
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
RDS(ON)P5 P-MOSFET, PVDD5 = 3.3V
--
6
15
Ω
RDS(ON)N5 N-MOSFET, PVDD5 = 3.3V
--
6
15
Ω
RDS(ON)P6 P-MOSFET, PVDD5 = 3.3V
--
6
15
Ω
RDS(ON)N6 N-MOSFET, PVDD5 = 3.3V
--
6
15
Ω
90
--
--
μA
5
40
10
50
15
60
μA
μA
SELECT = 0V
0.3
0.4
0.5
V
SELECT = 0V
--
1
--
V
VDDM = 3.3V
--
--
1.3
V
VDDM = 3.3V
0.4
--
--
V
VDDM = 3.3V
--
2
6
μA
Select Pin Input High Level Threshold
--
--
1.3
V
Select Pin Input Low Level Threshold
0.4
--
--
V
--
2
6
μA
125
180
--
°C
--
20
--
°C
Power Switch
CH5 On Resistance of MOSFET
CH6 On Resistance of MOSFET
Switch Controller
OK2 pin Sink Current
OK2 = 1V
External Current Setting (CH3)
CS3 Sourcing Current
VFB6 Sink Current
ICS3
IVFB6
Protection
Under Voltage Protection Threshold
Voltage @ FB1, FB2
Over Voltage Protection @ FB1, FB2
Control
EN1, EN2, EN3, EN4, EN5, EN6 Input
High Level Threshold
EN1, EN2, EN3, EN4, EN5, EN6 Input
Low Level Threshold
EN1, EN2, EN3, EN4, EN5, EN6 Sink
Current
Select Pin Sink Current
ISELECT
Thermal Protection
Thermal Shutdown
TSD
Thermal Shutdown Hysteresis
ΔTSD
Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for
stress ratings. 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 for extended
periods may remain possibility to affect device reliability.
Note 2. θJA is measured in the natural convection at T A = 25°C on a low effective thermal conductivity test board of
JEDEC 51-3 thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. A Schottky retifier connected from LX1 to PVDD1 is required for low-voltage startup, refer to Figure 1.
DS9911-05 April 2011
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11
RT9911
Typical Operating Characteristics
CH1 Buck Efficiency vs. Output Current
100
90
90
80
80
70
70
Efficiency (%)
Efficiency (%)
CH1 Boost Efficiency vs. Output Current
100
VIN = 3.2V
= 2.5V
= 2.0V
= 1.5V
60
50
40
30
20
10
0
60
VIN = 3.0V
= 3.4V
= 3.8V
= 4.5V
50
40
30
20
Ch1 Boost
VOUT = 3.3V
10
0
10
100
1000
Ch1 Buck
VOUT = 2.5V
10
100
Output Current (mA)
Output Current (mA)
CH1 Boost LX1 and
Output Voltage Ripple
CH1 Buck LX1 and
Output Voltage Ripple
VIN = 1.8V, VOUT = 3.3V, IOUT = 100mA
1000
VOUT
(10mV/Div)
VOUT
(10mV/Div)
LX1
(2V/Div)
LX1
(2V/Div)
VIN = 4.2V, VOUT = 3.3V, IOUT = 100mA
CH1 Boost Load Transient Response
CH1 Buck Load Transient Response
VIN = 3.0V, VOUT = 3.3V
VIN = 4.2V, VOUT = 3.3V
IOUT
(200mA/Div)
IOUT
(100mA/Div)
VOUT
(100mV/Div)
Time (1μs/Div)
VOUT
(100mV/Div)
Time (1μs/Div)
Time (1ms/Div)
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12
Time (1ms/Div)
DS9911-05 April 2011
RT9911
CH1 Buck Output Voltage vs. Output Current
3.375
3.29
3.374
3.28
3.373
Output Voltages (V)
Output Voltage (V)
CH1 Boost Output Voltage vs. VDDM Voltage
3.30
3.27
3.26
3.25
3.24
3.23
3.22
3.21
3.372
3.371
3.370
3.369
3.368
3.367
3.366
VIN = 2.5V, VOUT = 3.3V, IOUT = 250mA
VIN = 3.7V, VOUT = 3.3V
3.365
3.20
2.4
2.8
3.2
3.6
4.0
4.4
4.8
5.2
0
5.6
100
200
VDDM Voltage (V)
400
500
600
700
800
900
Loading Current (mA)
CH2 Buck Efficiency vs. Output Current
CH1 Boost Output Voltage vs. Output Current
3.330
100
3.329
90
3.328
80
3.327
70
Efficiency (%)
Output Voltages (V)
300
3.326
3.325
3.324
3.323
3.322
VIN = 2.5V
= 3.0V
= 3.8V
= 4.5V
60
50
40
30
20
3.321
10
VIN = 2.4V, VOUT = 3.3V
3.320
VOUT = 1.8V
0
100
200
300
400
500
600
700
800
900
10
100
1000
Output Current (mA)
CH2 LX2 and Output Voltage Ripple
CH2 LX2 and Output Voltage Ripple
VIN = 3.3V, VOUT = 1.8V, IOUT = 300mA
VIN = 4.2V, VOUT = 2.5V, IOUT = 400mA
LX2
(2V/Div)
Output Current (mA)
VOUT
(10mV/Div)
VOUT
(10mV/Div)
LX2
(2V/Div)
0
Time (1μs/Div)
DS9911-05 April 2011
Time (1μs/Div)
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13
RT9911
CH2 Load Transient Response
CH2 Load Transient Response
VIN = 3.3V, VOUT = 1.8V
VOUT
(20mV/Div)
IOUT
(100mA/Div)
IOUT
(200mA/Div)
VOUT
(20mV/Div)
VIN = 3.0V, VOUT = 2.5V
Time (1ms/Div)
Time (1ms/Div)
CH2 Output Voltage vs. VDDM Voltage
CH2 Load Transient Response
1.84
VIN = 4.2V, VOUT = 2.5V
VIN = 3.3V, VOUT = 1.8V, IOUT = 250mA
1.83
IOUT
(200mA/Div)
Output Voltage (V)
VOUT
(20mV/Div)
1.82
1.81
1.80
1.79
1.78
1.77
1.76
1.75
1.74
2.4
Time (1ms/Div)
2.8
3.2
3.6
4
4.4
4.8
5.2
5.6
VDDM Voltage (V)
CH2 Buck Output Voltage vs. Output Current
1.815
3.360
1.814
3.350
1.813
Output Voltages (V)
Output Voltages (V)
CH2 Buck Output Voltage vs. Output Current
3.370
3.340
3.330
3.320
3.310
3.300
3.290
3.280
VIN = 3.7V, VOUT = 3.3V
3.270
1.812
1.811
1.810
1.809
1.808
1.807
1.806
VIN = 3.7V, VOUT = 1.8V
1.805
0
100 200 300 400 500 600 700 800 900 1000
100
0
Output Current (mA)
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0
100 200 300 400 500 600 700 800 900 1000
100
0
Output Current (mA)
DS9911-05 April 2011
RT9911
CH3 Boost Efficiency vs. Output Current
100
90
90
80
80
70
VIN = 3.2V
= 2.5V
= 2.0V
= 1.5V
60
50
Efficiency (%)
Efficiency (%)
CH3 Boost Efficiency vs. Output Current
100
40
30
60
50
40
30
20
20
10
VIN = 4.5V
= 3.8V
= 3.2V
= 2.5V
= 2.0V
= 1.5V
70
10
VOUT = 3.3V
VOUT = 5V
0
0
10
100
10
1000
100
1000
Output Current (mA)
Output Current (mA)
CH3 Boost Efficiency vs. Output Current
CH3 LX3 and Output Voltage Ripple
100
VIN = 1.8V, VOUT = 3.3V, IOUT = 400mA
90
LX3
(2V/Div)
70
60
VIN = 3.0V Async
= 2.4V Async
= 1.5V Async
= 3.0V Sync
= 2.4V Sync
= 1.5V Sync
50
40
30
20
10
0
VOUT
(20mV/Div)
Efficiency (%)
80
VOUT = 3.3V
10
100
1000
Time (1μs/Div)
Output Current (mA)
CH3 LX3 and Output Voltage Ripple
CH3 Load Transient Response
VIN = 1.8V, VOUT = 5V, IOUT = 350mA
Time (1μs/Div)
DS9911-05 April 2011
IOUT
(200mA/Div)
VOUT
(20mV/Div)
LX3
(2V/Div)
VOUT
(100mV/Div)
VIN = 3.0V, VOUT = 3.3V
Time (1ms/Div)
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RT9911
CH3 Boost Output Voltage vs. VDDM Voltage
3.30
CH3 Boost Output Voltage vs. VDDM Voltage
5.08
VIN = 2.5V, VOUT = 3.3V, IOUT = 250mA
3.29
3.28
5.06
Output Voltage (V)
Output Voltage (V)
VIN = 2.5V, VOUT = 5.0V, IOUT = 250mA
5.07
3.27
3.26
3.25
3.24
3.23
3.22
5.05
5.04
5.03
5.02
5.01
5.00
3.21
4.99
3.20
4.98
2.4
2.8
3.2
3.6
4.0
4.4
4.8
5.2
5.6
2.4
2.8
3.2
VDDM Voltage (V)
5.010
80
5.005
Efficiency (%)
Output Voltage (V)
90
5.000
4.995
4.990
60
50
40
20
10
4.975
0
0.4
0.5
0.6
0.7
0.8
0.9
1
VOUT = 12V
1
10
Output Current (A)
Output Current (mA)
CH4 LX4 and Output Voltage Ripple
CH4 Load Transient Response
100
VIN = 1.8V, VOUT = 12V
IOUT
(20mA/Div)
VOUT
(20mV/Div)
LX4
(5V/Div)
VOUT
(100mV/Div)
VIN = 1.8V, VOUT = 12V, IOUT = 30mA
Time (1μs/Div)
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16
5.6
30
4.980
0.3
5.2
VIN = 4.5V
= 3.8V
= 3.2V
= 2.5V
= 2.0V
= 1.5V
70
4.985
0.2
4.8
CH4 Boost Efficiency vs. Output Current
VIN = 3.7V, VOUT = 5V
0.1
4.4
100
5.015
0
4
VDDM Voltage (V)
CH3 Boost Output Voltage vs. Output Current
5.020
3.6
Time (1ms/Div)
DS9911-05 April 2011
RT9911
CH4 Output Voltage vs. VDDM Voltage
CH4 Output Voltage vs. VDDM Voltage
11.88
15.42
VIN = 2.5V, PVDD5 = 3.3V, IOUT = 30mA
11.87
11.86
15.40
Output Voltage (V)
Output Voltage (V)
VIN = 2.5V, PVDD5 = 3.3V, IOUT = 30mA
15.41
11.85
11.84
11.83
11.82
11.81
11.80
11.79
15.39
15.38
15.37
15.36
15.35
15.34
15.33
11.78
15.32
2.4
2.8
3.2
3.6
4
4.4
4.8
5.2
5.6
2.4
2.8
3.2
VDDM Voltage (V)
70
Efficiency (%)
Output Voltages (V)
15.765
15.760
15.755
15.750
15.745
50
30
20
10
15.730
0
40
50
60
70
80
90
VIN = 1.5V
= 2.0V
= 2.5V
= 4.5V
= 3.2V
= 3.8V
40
15.735
30
100
VOUT = -8V
1
10
100
Output Current (mA)
Output Current (mA)
CH5 LX5 and Output Voltage Ripple
CH5 Load Transient Response
VIN = 1.8V, VOUT = -8V
IOUT
(20mA/Div)
VOUT
(20mV/Div)
VOUT
(100mV/Div)
LX5
(5V/Div)
VIN = 1.8V, VOUT = -8V, IOUT = 50mA
Time (1μs/Div)
DS9911-05 April 2011
5.6
60
15.740
20
5.2
90
80
10
4.8
CH5 Inverting Efficiency vs. Output Current
15.770
0
4.4
100
VIN = 3.7V, VOUT = 15.5V
15.775
4
VDDM Voltage (V)
CH4 Boost Output Voltage vs. Output Current
15.780
3.6
Time (1ms/Div)
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RT9911
CH5 Output Voltage vs. VDDM Voltage
CH5 Output Voltage vs. VDDM Voltage
-8.02
-6.02
VIN = 3.0V, PVDD5 = 3.3V, IOUT = 30mA
-8.03
-6.03
-6.04
Output Voltage (V)
-8.04
Output Voltage (V)
VIN = 3.0V, PVDD5 = 3.3V, IOUT = 30mA
-8.05
-8.06
-8.07
-8.08
-8.09
-6.05
-6.06
-6.07
-6.08
-6.09
-8.10
-6.10
-8.11
-6.11
-6.12
-8.12
2.4
2.8
3.2
3.6
4
4.4
4.8
5.2
2.4
5.6
2.8
3.2
4
4.4
4.8
5.2
5.6
VDDM Voltage (V)
VDDM Voltage (V)
CH6 Efficiency vs. Input Voltage
CH5 Output Voltage vs. Output Current
-8.152
100
-8.151
90
-8.150
80
-8.149
70
Efficiency (%)
Output Voltages (V)
3.6
-8.148
-8.147
-8.146
-8.145
IOUT = 20mA
60
50
40
30
20
-8.144
-8.143
10
VIN = 3.7V, VOUT = -8V
0
-8.142
0
-10
-20
-30
-40
-50
-60
-70
-80
1.5
-90 -100
2
2.5
3
3.5
4
4.5
Loading Current (mA)
Input Voltage (V)
CH6 LX6 and Output Voltage Ripple
CH7 Load Transient Response
VIN = 2.5V, VOUT = 1.8V
IOUT
(200mA/Div)
VOUT
(20mV/Div)
LX6
(5V/Div)
VOUT
(10mV/Div)
VIN = 1.8V, VOUT = 3 x WLED, IOUT = 20mA
Time (1μs/Div)
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5
Time (1ms/Div)
DS9911-05 April 2011
RT9911
CH1 and CH2 Power Sequence
VOUT_Ch5
(5V/Div)
VOUT_Ch2
(2V/Div)
VOUT_Ch4
(5V/Div)
VOUT_Ch1
(2V/Div)
EN4/EN5
(2V/Div)
EN1/EN2
(2V/Div)
CH4 and CH5 Power Sequence
Start Up, VIN = 2.5V
Time (1ms/Div)
Start Up, VIN = 2.5V
Time (2ms/Div)
Feedback Voltage vs. Temperature
1.04
Feedback Voltage (V)
1.00
VFB4, VFB6
0.96
0.92
0.88
0.84
VFB1, VFB2, VFB3
0.80
0.76
0.72
-40
-20
0
20
40
60
80
100
Temperature (°C)
DS9911-05 April 2011
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19
RT9911
Applications Information
The RT9911 includes the following six DC/DC converter
channels to build a multiple-output power-supply system.
CH1 : Selectable step-up or step-down synchronous
current mode DC/DC converter with internal power
MOSFETs.
CH2 : Step-down synchronous current mode DC/DC
converter with internal power MOSFETs.
CH3 : Step-up asynchronous current mode DC/DC
controller to drive external power MOSFETs.
CH4 : Step-up asynchronous voltage mode DC/DC
controller.
CH5 : Inverting DC/DC voltage mode controller.
CH6 : DC/DC voltage mode controller for WLED as well as
conventional boost application; provides open LED OVP
protection.
CH1 : Selectable Step-up or Step-down Converter
CH1 is selectable as step-up (SELECT pin = logic high)
or step-down (SELECT pin = logic low).
Step-up : With internal MOSFETs and synchronous
rectifier, the efficiency is up to 95%. The converter always
operates at fixed frequency PWM mode and CCM
(continuous current mode).
Step-down : With internal MOSFETs and synchronous
rectifier, the efficiency is up to 95%. The converter always
operates at fixed frequency PWM mode and CCM. While
the input voltage is close to output voltage, the converter
enters low dropout mode. Duty could be as long as 100%
to extend battery life. See Figure 3(a) for detailed functional
block.
CH3 : Step-up DC/DC Controller
With external MOSFETs and a synchronous rectifier, the
efficiency is up to 97%. The converter always operates at
fixed frequency PWM mode and CCM. The threshold of
current limit is estimated by RDS(ON) of external NMOS.
See Protections for detailed information and detailed
functional block in Figure 3(c).
CH4, CH6 : Step-up DC/DC Controller
CH4 and CH6 are fixed frequency voltage mode PWM
controllers. EXT4 and EXT6 pins are designed to drive
external NMOS switch. CH6 is optimized for WLED
application. CFB6 is current-sensing feedback, and VFB6
provides over voltage protection (WLED open circuit). See
Protections for detailed information and detailed functional
block in Figure 3(d for CH4 and e for CH6).
CH5 : Inverting Controller
CH5 is a voltage mode, fixed frequency PWM controller
to generate negative output voltage. EXT5 is designed to
drive external PMOS switch. To turn off PMOS completely,
please note that PVDD5 should not be lower than the
source voltage of PMOS. See Figure 3(f) for detailed
functional block.
Reference Voltage
RT9911 provides a precise 1V reference voltage with
souring capability 100μA. Connect a 1μF ceramic capacitor
from VREF pin to GND. Reference voltage is enabled by
connecting EN5 to logic high.
CH2 : Step-down DC/DC Converter
With internal MOSFETs and synchronous rectifier, the
efficiency is up to 95%. The converter always operates at
fixed frequency PWM mode and CCM. While the input
voltage is close to output voltage, the converter enters
low dropout mode. Duty could be as long as 100% to
extend battery life. See Figure 3(b) for detailed functional
block.
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20
DS9911-05 April 2011
RT9911
PVDD2
PVDD1
OSC
COMP1
0.8V
FB1
SELECT
S Q
+
+
-
-
Logic
R
Driver
LX1
OSC
COMP2
0.8V
FB2
Current
Sense
S Q
+
+
-
-
R
Logic
Driver
Current
Sense
Slope
compensation
PGND1
Fault
Protection
Slope
compensation
Figure 3(a)
PGND2
Fault
Protection
Figure 3(b)
PVDD3
OSC
COMP3
0.8V
FB3
CS3
S Q
+
+
-
-
LX2
DRP3
Logic
R
Driver
PVDD5
OSC
COMP4
1.0V
FB4
+
-
DRN3
Current
Sense
Slope
compensation
PGND2
Fault
Protection
S Q
+
-
R
Logic
Driver
EXT4
GND
Triangle
Wave
Figure 3(d)
Figure 3(c)
PVDD5
OSC
COMP6
CFB6
0.2V
EN6
+
+
-
S Q
+
-
Logic
R
Driver
EXT6
PVDD5
OSC
COMP5
FB5
GND
+
-
S Q
+
-
R
Logic
Driver
EXT5
Diming
Control
Triangle
Wave
Fault
Protection
GND
GND
Triangle
Wave
Figure 3(e)
Figure 3(f)
Figure 3. Detailed Functional Block for each channel
DS9911-05 April 2011
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21
RT9911
VBAT
VDDM (VS 3.3V)
EN1 to EN6
VS 3.3V
T1r
T1d
VCORE 1.8V
VI/O 3.3V
T2d T2r
Motor 5V
T3d
T3r
CCD 12V
CCD - 8V
T4d
T4r
T5d T5r
WLED
T6d
Note :
z
Please refer to Figure 1 for application Information.
z
Timing sequence should be controlled by EN pins.
T6r
Figure 4. Timing Diagram
Calculation method:
Units : T in second, C in Farad, R in Ohm
T3r = (0.5V x D3 + 0.8A x RDS(ON)_N x C33 /3.6μA @ No
load
C31 to C36 : Compensation capacitor of CH1 to CH6.
T4r = (1.0V x D4) x C34 / 1μA @ No load
T1d = 0.7V x C31 / 2μA (CH1 Boost)
T5r = (1.0V x D5) x C35 / 1μA @ 1mA min. load
T1d = 0.7V x C31 / 2μA (CH1 Buck)
T6r = (0.25V x D6) x C36 / 2.6μA @ 4 WLEDs
T2d = 0.35V x C32 / 2μA
where
T3d = 0.7V x C33 / 2μA
D1 = 1 − (VBAT / VVS 3.3V) (Boost)
T4d = 0.35V x C34 / 2μA
D1 = VVS 3.3V / VBAT
T5d = 0.85V x C35 / 2μA
D2 = VVCORE 1.8V / VBAT
T6d = 0.85V x C36 / 2μA
D3 = 1 − (VBAT / VMotor 5V)
Td1 to Td6 are precise value. Tr1 to Tr6 are approximation.
T1r = (0.5V x D1 + 0.48A x RDS(ON)_N x C31 /1.25μA @ No
load (Boost)
(Buck)
D4 = 1 − (VBAT / VCCD 12V)
D5 = |VCCD -8V| / ( VBAT + |VCCD -8V|)
T1r = (0.33V x D1 + 0.2A x RDS(ON)_P x C31 /1.25μA @ No
load (Buck)
D6 = 1 − (VBAT / VWLED)
T2r = (0.33V x D2 + 0.2A x RDS(ON)_P x C32 /1.25μA @ No
load
T1r = (0.5 x (1−1.8/3.3) + 0.48 x 0.2) x 1nF / 1.25μA =
258μs
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22
Example : T1d = 0.7V x 1nF / 2μA = 350μs (Boost)
DS9911-05 April 2011
RT9911
Oscillator
Soft Start
With internal soft start mechanism, the soft start time of
each channel is proportional to the compensation capacitor.
Refer to the soft start waveform in Figure 4 for typical
application.
Oscillator Frequency vs. RRT
2500
Oscillator Frequency (kHz)1
The internal oscillator synchronizes CH1 to CH6 with fixed
operation frequency. The frequency could be set by
connecting resistor between RT pin to GND. See Figure 5
to adjust frequency.
2250
2000
1750
1500
1250
1000
750
500
250
0
Protection
10
RT9911 provides versatile protection functions. Protection
type, threshold and protection methods are summarized
in Table 1.
100
1000
RRT (kΩ)
Figure 5. Adjust Frequency
Table 1
VDDM
CH1:
Boost
Protection
Threshold (typical)
type
Refer to Electrical spec
Over Voltage
Protection
Current Limit
Current Limit
CH1:
Under Voltage
Buck
Protection
Over Voltage
Protection
Current Limit
CH2
Under Voltage
Protection
Over Voltage
Protection
CH3
CH6
Thermal
Current Limit
VDDM > 6.5V
Disable all channels
NMOS current> 2.5A
NMOS latched off
PMOS current > 2.0A
FB1 < 0.4V
FB1 > 1.0V
PMOS current > 2.0A
FB2 < 0.4V
FB2 > 1.0V
CS3 > 0.3V, see below
Note
Over Voltage
VFB6 > 1.0V, see
Protection
Figure 8
Thermal
shutdown
Protection methods
Temperature > 180°C
PMOS latched off and all
channels shutdown
NMOS, PMOS latch off and
all channels shutdown
NMOS, PMOS latch off and
all channels shutdown
PMOS latched off and all
channels shutdown
NMOS, PMOS latch off and
all channels shutdown
NMOS, PMOS latch off and
all channels shutdown
NMOS latched off
Reset method
Restart if VDDM < 6.5V
Automatic reset at next clock
cycle
VDDM power reset
VDDM power reset
VDDM power reset
VDDM power reset
VDDM power reset
VDDM power reset
Automatic reset at next clock
cycle
NMOS off
VFB6 < 1.0V
All channels stop switching
Temperature < 160°C
Note : If RDS(ON) x Iinductor > 0.3V, then current limit happens.
For example, if select NMOS( AOS3402), RDS(ON) =110mΩ (at VGS = 2.5V), then current limt happens if Iinductor > 2.73A.
DS9911-05 April 2011
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23
RT9911
VBAT
VBAT
VDDM
WLED
EXT6
10µA
R
LX3
CH3
PWM
VFB6
CS3
-
1V
50µA
Iinductor
DRN3
+
CH6
PWM
CFB6
Figure 6. CH3 Current Limit Setting
Figure 8. CH6 Over Voltage Protection Method
(VWLED > 50μA x R+1V, protection happens)
RT9911 Component Selection for Compensation :
CH1 Sync-Boost (Select Pin = High Logic) :
CH1 sync-boost converter employs current-mode control
to simplify the control loop compensation. There is a RHPZ
(Right Hand Plane Zero) appeared in the loop-gain
frequency response when a boost converter operates with
continuous inductor current (typically the case), we also
call it works in CCM (Continuous Current Mode). For
stability, cross over frequency (fC), unity gain frequency,
must lower than this RHPZ frequency.
The fixed parameters for CH1 boost compensation are as
follows :
z
Transconductance (from FB to COMP), GM = 200μs
z
Current sense transresistance, RCS = 0.4V/A
z
Feedback voltage, VFB = FB = 0.8V
COMP
CP
RC
0.8V
R1
R2
VIN, input voltage.
z
VOUT, desired output voltage
z
IOUT(MAX.), maximum output load
z
FOSC, operating frequency
z
L, inductance
z
RESR, ESR (Equivalent Series Resistance) of COUT
(ceramic output capacitor)
TDRP(%), Transient droop.
The results we will get for CH1 boost compensation are
as follows:
RESR
IOUT
z
R2, the voltage divider resistor in between FB and ground.
z
CF, feedforward capacitor in parallel with R1.
z
RC, compensation resistor on COMP pin.
COUT
z
Figure 7
R1, the voltage divider resistor in between VOUT and
FB.
z
z
FB
CC
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24
CF
z
z
VOUT
+
GM
-
The input parameters for CH1 boost compensation are as
follows:
z
CC, compensation capacitor in series with Rc and
connect to ground.
CP, connect in between COMP pin and ground. (Can be
ignored if CP < 10pF).
COUT, output capacitance. This compensation is based
on ceramic output capacitor.
DS9911-05 April 2011
RT9911
The major steps for getting above results :
⎞
VFB
1. R2 = R1 x ⎛⎜
⎜ (VOUT - VFB) ⎟⎟
⎝
⎠
RLOAD
GM
⎛ VFB ⎞
RCS
x⎜
⎟ x (1 − D) = 6.3nF.
4. CC =
2πfC
⎝ VOUT ⎠
Choose 6.8nF.
Half-load transient means load from 0.25A to 0.5A
transient. So, dI=0.5 − 0.25=0.25A
2. Find RHPZ(Right Hand Plan Zero) location.
RHPZ(Boost) = RLOAD x
RLOAD =
VOUT
IOUT(MAX.)
2
(1 - D)
, Where
2πL
, D = Duty Cycle = 1 -
VIN
VOUT
3. Set fC (cross over frequency) sufficiently below RHPZ.
For example : fC = RHPZ/6
V FB
⎛ R LOAD ⎞ GM
x
x (1 - D)
⎟x
4. Get C C = ⎜
⎝ R CS ⎠ 2π f C V OUT
5. Select Rc based on the allowed transient droop.
1
RCS
RC = dI x (
)x
(1- D) GM x dVFB
, where dI = transient step, dVFB = TDRP(%) x VFB
RC x CC
6. Get COUT =
RLOAD
7. Find ffz, zero and ffp, pole ratio of voltage divider with
CF.
ffz VOUT
ratio =
=
ffp
VFB
fC
8. Get CF by placing ffp on fC and ffz therefore on
.
ratio
1
fC
Cf =
, where ffz =
2 x π x ffz x R1
ratio
9. Evaluate CP. CP is for canceling the zero from COUT
(ceramic output capacitor).
RESR
CP = COUT
. CP can be ignore if CP < 10pF.
RC
Example : Set R1 = 470kΩ, VIN = 1.8V, VOUT = 3.3V,
VFB = 0.8V, IOUT(MAX.) = 0.5A, fOSC = 500kHz, L = 4.7μH,
RESR = 5mΩ, and half-load transient droop is 5%.
Results:
1. R2 = R1
VFB
0.8
= 470k
= 150k Ω
VOUT - VFB
3.3 - 0.8
2
(1 - D)
= 66.3kHz, where
2πL
VOUT
VIN
RLOAD =
= 6.6Ω , (1 - D) =
= 0.54
IOUT(MAX)
VOUT
2. RHPZ(Boost) = RLOAD
3. fC =
RHPZ
= 11kHz
6
dVFB = TDRP(%) x VFB = 5% x 0.8 = 0.04V.
Thus,
⎛ 1 ⎞
⎟ x RCS
dI⎜⎜
(1 - D) ⎟⎠
⎝
= 23kΩ
5. RC =
GM x dVFB
6. COUT =
7. ratio =
ffp VOUT 3.3
=
=
= 4.1
ffz
VFB
0.8
1
= 126pF, where
2π × ff Z × R1
fC
11k
ff Z =
=
= 2.68kHz
ratio 4.1
8. CF =
Choose CF = 150pF
COUT x RESR 22μF x 0.005
=
= 4.8pF ,
9. CP =
RC
23k
which is less than 10pF. So, It can be ignored.
CH1 Sync-Buck (Select Pin = Low Logic) and CH2
Sync-Buck :
CH1 sync-buck (select pin=low logic) and CH2 sync-buck
are converters employ current-mode control to simplify
the control loop compensation. There is no RHPZ (Right
Hand Plan Zero) in the buck topology but there is a high
frequency pole f HP >= f OSC /π . The f C (cross over
frequency) is chosen sufficient less than fHP.
The fixed parameters for CH1 and CH2 buck compensation
are as follows:
z
Transconductance (from FB to COMP), GM = 200μs
z
Current sense transresistance, RCS = 0.3V/A
z
Feedback voltage, VFB = FB = 0.8V
The input parameters for CH1 and CH2 buck compensation
are as follows:
z
DS9911-05 April 2011
RC x CC 23k x 6.8n
=
= 22 μF .
RLOAD
6 .6
R1, the voltage divider resistor in between VOUT and
FB.
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25
RT9911
z
VIN, input voltage.
z
VOUT, desired output voltage
z
IOUT(MAX.), maximum output load
z
fOSC, operating frequency
8. Evaluate CP. CP is for canceling the zero from COUT
(ceramic output capacitor).
COUT x RESR
CP =
. CP can be ignore if CP < 10pF.
RC
Example : Set R1 = 470kΩ, VIN = 3V, VOUT = 1.8V,
z
L, inductance
VFB = 0.8V, IOUT(MAX.) = 0.5A, fOSC = 500kHz, L = 4.7μH,
RESR, ESR (Equivalent Series Resistance) of COUT
(ceramic output capacitor)
RESR = 5mΩ, and half-load transient droop is 5%.
TDRP(%), Transient droop.
Results :
z
z
The results we will get for CH1 boost compensation are
as follows:
z
R2, the voltage divider resistor in between FB and ground.
z
CF, feedforward capacitor in parallel with R1.
z
RC, compensation resistor on COMP pin.
z
z
z
CC, compensation capacitor in series with RC and
connect to ground
CP, connect in between COMP pin and ground. (Can be
ignored if CP < 10pF)
COUT, output capacitance. This compensation is based
on ceramic output capacitor.
1. R2 = R1 x
2. fC =
VFB
0.8
= 470k x
= 376k Ω
VOUT - VFB
1.8 - 0.8
fHP fOSC
=
= 40kHz
4
4π
RLOAD GM
VFB
x
x
= 4.25nF, where
RCS
2πfC VOUT
VOUT
RLOAD =
= 3.6Ω
IOUT(MAX.)
3. CC =
Choose 4.7nF.
Half-load transient means load from 0.25A to 0.5A
transient. So, dI = 0.5 − 0.25=0.25A
dVFB = TDRP(%) x VFB = 5% x 0.8 = 0.04V.
The major steps for getting above results :
VFB
1. R2 = R1
VOUT - VFB
2. Set fc (cross over frequency) sufficiently below fOSC.
fHP
For example : fC =
4
3. CC =
RLOAD GM
VFB
x
x
RCS
2πfC VOUT
dI x RCS
4. RC = GM x dVFB , where dI = transient step,
dVFB = TDRP(%) x VFB
RC x CC
RLOAD
6. Find ffz, zero and ffp, pole ratio of voltage divider with
CF.
ffp VOUT
ratio =
=
ffz
VFB
fC
7. Get CF by placing ffp on fC and ffz therefore on
.
ratio
1
fC
CF =
, where ff Z =
.
2π × ff Z × R1
ratio
5. Get COUT =
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26
Thus,
4. RC = dI
RCS
= 9.4k Ω , choose 10k Ω.
GM x dVFB
5. COUT = RC x CC = 10k x 3.9nF = 10.8 μF. Choose 10 μF.
RLOAD
3 .6
6. ratio =
ffp VOUT 1.8
=
=
= 2.25
ffz
VFB
0.8
1
= 15.2pF, where
2π × ff Z × R1
fC
50k
ff Z =
=
= 22.2kHz
ratio 2.25
7. CF =
Choose CF = 22pF
COUT x RESR 10 μ x 0.005
8. CP =
=
= 5pF ,
RC
10k
which is less than 10pF. So, It can be ignored.
DS9911-05 April 2011
RT9911
CH3 Syn Boost Controller with External MOSFET :
CH3 boost controller driving external logic level MOSFET
employs current-mode control to simplify the control loop
compensation. There is a RHPZ (Right Hand Plan Zero)
appeared in the loop-gain frequency response when a
boost converter operates with continuous inductor current
(typically the case), we also call it works in CCM
(Continuous Current Mode). For stability, cross over
frequency (fC), unity gain frequency, must lower than this
RHPZ frequency.
The fixed parameters for CH3 boost compensation are as
follows :
z
Transconductance (from FB to COMP), GM = 200μs
z
Feedback voltage, VFB = FB = 0.8V
The input parameters for boost compensation are as
follows :
z
z
RDS(ON), the NMOSFET RDS(ON), which is use to find
transresistance, RCS.
R1, the voltage divider resistor in between VOUT and
FB.
z
COUT, output capacitance. This compensation is based
on ceramic output capacitor.
The major steps for getting above results :
1. RCS = 2 x RDS(ON)
The rest of the steps are the same as sync-boost.
CH4 Asyn-Boost Controller with External MOSFET
CH4 is an asyn-boost controller driving external logic level
N type MOSFET, which employs voltage mode control to
regulate the output voltage. Compensation depends on
designing the loading range working in discontinuous or
continuous inductor current mode. (DCM or CCM).
Asyn-Boost in DCM :
We call it DCM because inductor current falls to zero on
each switch cycle. The benefit of designing in DCM is the
simple loop compensation, which has no RHPZ (Right
Hand Plan Zero) and conjugate double pole in the frequency
domain to worry about, but has a single load pole instead.
However, the output ripple and efficiency are worse than
in CCM (Continuous Inductor Current). If the loading is
around tens of mA, it is not bad to design in DCM with
less impact on the output ripple and efficiency, but gain
more easy to stabilize the control loop.
z
VIN, input voltage.
z
VOUT, desired output voltage
z
IOUT(MAX.), maximum output load
z
FOSC, operating frequency
The fixed parameters for CH4 asyn-boost in DCM
compensation are as follows:
z
L, inductance
z
Transconductance (from FB to COMP), GM = 200us.
RESR, ESR (Equivalent Series Resistance) of COUT
(ceramic output capacitor)
z
Internal voltage ramp to decide duty cycle, VP = 1V.
z
Feedback voltage, VFB = FB = 1V
z
z
TDRP(%), Transient droop.
VOUT
The results we will get for boost compensation are as
follows :
z
RCS, the transresistance of current sense.
z
R2, the voltage divider resistor in between FB and ground.
z
CF, feedforward capacitor in parallel with R1.
z
RC, compensation resistor on COMP pin.
z
z
CC, compensation capacitor in series with RC and
connect to ground
+
GM
-
COMP
CP
RC
1V
R1
FB
R2
CF
RESR
IOUT
COUT
CC
Figure 9
CP, connect in between COMP pin and ground. (Can be
ignored if CP < 10pF)
DS9911-05 April 2011
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27
RT9911
The input parameters for CH4 asyn-boost in DCM
compensation are as follows :
z
R1, the voltage divider resistor in between VOUT and
FB.
z
VIN, input voltage.
z
VOUT, desired output voltage
z
IOUT(MAX.), maximum output load
z
fOSC, operating frequency
z
L, inductance
z
z
COUT, output capacitance. This compensation is based
on ceramic output capacitor.
RESR, ESR (Equivalent Series Resistance) of COUT
(ceramic output capacitor)
The results we will get for CH4 asyn-boost in DCM
compensation are as follows :
z
R2, the voltage divider resistor in between FB and ground.
z
CF, feedforward capacitor in parallel with R1.
z
RC, compensation resistor on COMP pin.
z
z
CC, compensation capacitor in series with RC and
connect to ground
CP, connect in between COMP pin and ground. (Can be
ignored if CP < 10pF)
The major steps for getting above results :
VFB
1. R2 = R1 x
VOUT - VFB
2. Select suitable inductor to ensure IOUT(MIN.) works in
DCM, which is let inductor current falls to zero on each
switch cycle.
VIN x D x (1 - D)
L<
2 x IOUT(MAX.) x fOSC
3. Set fC sufficient below fOSC.
fOSC
For example: fC =
or lower
10
2 x M-1
,
2π x (M - 1) x RLOAD x COUT
VOUT
VOUT
where M =
, RLOAD =
.
VIN
IOUT(MAX.)
4. Find the load pole : fLP =
fC
x VP
VOUT
M-1
, where Gdod = 2 x
x
,
5. Get RC = fLP
GM x Gdod
D
2 x M-1
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28
which is duty to VOUT transfer function.
VIN
D = duty cycle = 1 VOUT
RLOAD
RC
by letting comp zero = load pole.
6. Get CC = COUT x
7. Find ffz, zero and ffp, pole ratio of voltage divider with
CF.
ffp VOUT
ratio =
=
ffz
VFB
fC
8. Get CF by placing ffp on fC and ffz therefore on
.
ratio
CF =
1
fC
, where ff Z =
.
2π × ff Z × R1
ratio
9. Evaluate CP. CP is for canceling the zero from COUT
(ceramic output capacitor).
CP = COUT x
RESR
. CP can be ignore if CP < 10pF.
RC
Asyn-boost in CCM :
We call it CCM because inductor current is always
continuous in operation. The benefit of designing in CCM
is lower VOUT and inductor current ripple and higher
efficiency from the lower coil loss, but with the expense
of larger inductor size and cost and the control loop comes
with a RHPZ (Right Hand Plan Zero) and a conjugate double
pole in the frequency domain to worry about.
The fixed parameters for CH4 asyn-boost in CCM
compensation are as follows :
z
Transconductance (from FB to COMP), GM = 200μs
z
Internal voltage ramp to decide duty cycle, VP = 1V
z
Feedback voltage, VFB = FB = 1V
The input parameters for CH4 asyn-boost in CCM
compensation are as follows :
z
R1, the voltage divider resistor in between VOUT and
FB.
z
VIN, input voltage.
z
VOUT, desired output voltage
z
IOUT(MAX.), maximum output load
z
IOUT(MIN.), minimum output laod
z
fOSC, operating frequency
DS9911-05 April 2011
RT9911
z
z
z
L, inductance
COUT, output capacitance. This compensation is based
on ceramic output capacitor.
RESR, ESR (Equivalent Series Resistance) of COUT
(ceramic output capacitor)
The results we will get for CH4 asyn-boost in CCM
compensation are as follows:
z
R2, the voltage divider resistor in between FB and ground.
z
CF, feedforward capacitor in parallel with R1.
z
RC, compensation resistor on COMP pin.
z
z
CC, compensation capacitor in series with RC and
connect to ground
CP, connect in between COMP pin and ground. (Can be
ignored if CP < 10pF)
The major steps for getting above results :
VFB
1. R2 = R1 x
VOUT - VFB
2. Select suitable inductor to ensure IOUT(MIN.) works in
CCM,
VIN x D x (1 - D)
L>
2 x IOUT(MIN.) x fOSC
3. Find RHPZ(Right Hand Plan Zero) location.
RHPZ(Boost) = RLOAD
RLOAD =
VOUT
IOUT(MAX)
(1 - D)2
, where
2πL
, D = duty cycle = 1 -
VIN
VOUT
4. Set fC (cross over frequency) sufficiently below RHPZ.
RHPZ
or lower.
For example : fC =
6
2 x M-1
5. Find the load pole : fLP =
,
2π x (M - 1) x RLOAD x COUT
VOUT
VOUT
where M =
, RLOAD =
.
VIN
IOUT(MAX.)
fC
x VP
VIN
f
LP
Get
R
, where Gdoc =
C
=
,
6.
GM x Gdoc
(1 - D)2
which is duty to VOUT transfer function.
VIN
D = duty cycle = 1 .
VOUT
1- D
,
7. Find fcdp =
2π x (LC)2
which is the conjugate double pole from LC filter.
1
to cancel one of the double pole.
8. CC =
2π x fcdp x RC
9. Find Cf by placing its zero on fcdp to cancel another
double pole.
1
CF =
.
2π × fcdp × R1
10.Evaluate CP. CP is for canceling the zero from COUT
(ceramic output capacitor).
RESR
CP = COUT x
. CP can be ignore if CP < 10pF.
RC
CH5 Asyn-Inverter Controller with External MOSFET
CH5 is an asyn-inverter controller driving external logic
level P type MOSFET, which employs voltage mode
control to regulate the output voltage. Compensation
depends on designing the loading range working in
discontinuous or continuous inductor current mode. (DCM
or CCM).
Asyn-Inverter in DCM :
We call it DCM because inductor current falls to zero on
each switch cycle. The benefit of designing in DCM is the
simple loop compensation, which has no RHPZ (Right
Hand Plan Zero) and conjugate double pole in the frequency
domain to worry about, but has a single load pole instead.
However, the output ripple and efficiency are worse than
in CCM (Continuous Inductor Current). If the loading is
around tens of mA, it is not bad to design in DCM with
less impact on the output ripple and efficiency, but gain
more easy to stabilize the control loop.
The fixed parameters for CH5 asyn-inverter in DCM
compensation are as follows:
z
Transconductance (from FB to COMP), GM = 200μs
z
Internal voltage ramp to decide duty cycle, VP = 1V
z
Feedback voltage, VFB = FB = 0V
z
Reference voltage, VREF = 1V
VOUT
+
GM
-
COMP
CP
RC
0V
R1
CF
FB
R2
CC
RESR
IOUT
COUT
VREF = 1V
20k
4.7uF
Figure 10
DS9911-05 April 2011
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RT9911
The input parameters for CH5 asyn-inverter in DCM
compensation are as follows :
z
R1, the voltage divider resistor in between VOUT and
FB.
z
VIN, input voltage.
z
VOUT, desired output voltage
z
IOUT(MAX.), maximum output load
z
fOSC, operating frequency
z
L, inductance
z
z
COUT, output capacitance. This compensation is based
on ceramic output capacitor.
RESR, ESR (Equivalent Series Resistance) of COUT
(ceramic output capacitor)
The results we will get for CH5 asyn-inverter in DCM
compensation are as follows :
z
R2, the voltage divider resistor in between FB and VREF.
z
CF, feedforward capacitor in parallel with R1.
z
RC, compensation resistor on COMP pin.
z
z
fC
x VP
VOUT
f
LP
Get
R
, where Gdod =
,
C=
5.
GM x Gdod
D
CC, compensation capacitor in series with RC and
connect to ground
CP, connect in between COMP pin and ground. (Can be
ignored if CP < 10pF)
The major steps for getting above results :
VREF - VFB
. If R1 = 1MΩ and VOUT = (-8)V
1. R2 = R1 x
VFB − VOUT
1- 0
then R2 = 1M x
= 125k Ω
0 - (-8)
2. Select suitable inductor to ensure IOUT(MIN.) works in
DCM, which is let inductor current falls to zero on each
switch cycle.
L<
VIN x (1 - D)
2 x IOUT(MAX.) x fOSC
3. Set fC sufficient below fOSC
fOSC
For example: fC =
or lower
10
2
,
4. Find the load pole : fLP =
2π x RLOAD x COUT
VOUT
where RLOAD =
.
IOUT(MAX.)
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30
which is duty to Vout transfer function.
D = duty cycle =
abs(VOUT)
.
VIN + abs(VOUT)
RLOAD
RC
by letting comp zero = load pole.
6. Get CC = COUT x
7. Find ffz, zero and ffp, pole ratio of voltage divider with
CF.
ffp abs(VOUT) + VREF
ratio =
=
ffz
VREF
fC
8. Get CF by placing ffp on fC and ffz therefore on
.
ratio
1
fC
CF =
, where ff Z =
.
2π × ff Z × R1
ratio
9. Evaluate CP. CP is for canceling the zero from COUT
(ceramic output capacitor).
CP = COUT x
RESR
. CP can be ignore if CP < 10pF.
RC
Asyn-Inverter in CCM :
We call it CCM because inductor current is always
continuous in operation. The benefit of designing in CCM
is lower VOUT and inductor current ripple and higher
efficiency from the lower coil loss, but with the expense
of larger inductor size and cost and the control loop comes
with a RHPZ (Right Hand Plan Zero) and a conjugate double
pole in the frequency domain to worry about.
The fixed parameters for CH5 asyn-inverter in CCM
compensation are as follows :
z
Transconductance (from FB to COMP), GM = 200us
z
Internal voltage ramp to decide duty cycle, VP = 1V
z
Feedback voltage, VFB = FB = 0V
z
Reference voltage, VREF = 1V
The input parameters for CH5 asyn-inverter in CCM
compensation are as follows :
z
R1, the voltage divider resistor in between VOUT and
FB.
z
VIN, input voltage.
z
VOUT, desired output voltage
z
IOUT(MAX.), maximum output load
DS9911-05 April 2011
RT9911
z
IOUT(MIN.), minimum output laod
z
fOSC, operating frequency
z
L, inductance
z
z
COUT, output capacitance. This compensation is based
on ceramic output capacitor.
RESR, ESR (Equivalent Series Resistance) of COUT
(ceramic output capacitor)
The results we will get for CH5 asyn-inverter in CCM
compensation are as follows :
z
R2, the voltage divider resistor in between FB and VREF.
z
CF, feedforward capacitor in parallel with R1.
z
RC, compensation resistor on COMP pin.
z
z
7. Find fcdp =
,
2π x (LC)2
which is the conjugate double pole from LC filter.
1
to cancel one of the double pole.
8. CC =
2π x fcdp x RC
9. Find Cf by placing its zero on fcdp to cancel another
double pole.
1
CF =
.
2π × fcdp × R1
10.Evaluate CP. CP is for canceling the zero from COUT
(ceramic output capacitor).
CP = COUT x
RESR
. CP can be ignore if CP < 10pF.
RC
PCB Layout Considerations
CC, compensation capacitor in series with RC and
connect to ground
z
CP, connect in between COMP pin and ground. (Can be
ignored if CP < 10pF)
z
The major steps for getting above results :
VREF - VFB
. If R1 = 1MΩ and VOUT = (-8)V
1. R2 = R1 x
VFB − VOUT
1- 0
then R2 = 1M x
= 125k Ω
0 - (-8)
1- D
z
z
The feedback netwok should be very close to the FB
pin.
The compensation network should be very close to the
COMP pin and avoid through VIA.
For CH3 current sense, CS should be close to the drain
site of external NMOS.
Keep high current path as short as possible.
2. Select suitable inductor to ensure IOUT(MIN.) works in
CCM,
VIN x (1 - D)
L<
2 x IOUT(MIN.) x fOSC
3. Find RHPZ(Right Hand Plan Zero) location.
(1 - D)2
D , where
RHPZ(Boost) = RLOAD
2πL
VOUT
abs(VOUT)
RLOAD =
, D = duty cycle =
IOUT(MAX)
VIN + abs(VOUT)
4. Set fC (cross over frequency) sufficiently below RHPZ.
RHPZ
For example: fC =
or lower
6
2
,
5. Find the load pole : fLP =
2π x RLOAD x COUT
abs(VOUT)
where RLOAD =
.
IOUT(MAX.)
fC
x VP
VIN
, where Gdoc =
,
6. Get RC = fLP
GM x Gdoc
(1 - D)2
which is duty to VOUT transfer function.
D = duty cycle =
abs(VOUT)
VOUT
VIN + abs(VOUT)
DS9911-05 April 2011
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RT9911
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.
Symbol
Dimensions In Millimeters
Dimensions In Inches
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
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: [email protected]
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit
design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be
guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
www.richtek.com
32
DS9911-05 April 2011
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