RICHTEK RT9901

RT9901
Preliminary
4 Channel DC/DC Converters IC with High-Efficiency Step-Up
and Step-Down
General Description
Features
The RT9901 is a complete power-supply solution for digital
still cameras and other hand-held devices. It integrates a
high-efficiency main step-up DC-DC converter, two highefficiency step-down converters, a charge pump, and
voltage detector. The RT9901 is targeted for applications
that use either two or three AA cells or a single lithiumion
battery.
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Applications
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Pin Configurations
Note :
`Suitable for use in SnPb or Pb-free soldering processes.
`100% matte tin (Sn) plating.
ENM
COMP2
EN2
EN1
26 25
24
VDD2
VDD3
LX3
2
23
VDD2
3
22
LX2
PGND3
SS
RT
4
21
GND
7
18
LX2
PGND2
LX1
LX1
LBO
8
17
VDD1
GND
5
20
6
19
33
VDDM
9
10 11 12
13 14
15 16
PGND1
ments of IPC/JEDEC J-STD-020.
28 27
1
CX
`RoHS compliant and compatible with the current require-
31 30 29
COMP3
VDDC
Richtek Pb-free and Green products are :
32
FB2
(TOP VIEW)
CPFB
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commercial Standard)
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EN3
Package Type
QV : VQFN-32L 5x5 (V-Type)
COMP1
RT9901
Digital Still Camera
PDAs
Portable Device
GND
Ordering Information
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FB1
RT9901 is available in VQFN-32L 5x5 package.
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FB3
The feature of the charge pump is to deliver few current
to micro-controller when the system operates in the
standby mode. RT9901 include a low battery detector with
0.8V detection voltage. An adjustable operating frequency
(up to 1.4MHZ) is utilized to get optimum size, cost, and
efficiency.
LBI
The main step-up DC-DC converter accepts inputs from
1.5V to 5.5V and build in 2.6A Internal switch. The two
step-down DC-DC converters (CH2, CH3) accept inputs
from 1.5V to 5.5V and regulate a resistor-adjustable output
from 0.8V to 5.5V. Each DC-DC converters have
independent shutdown inputs.
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1.5V to 5.5V Battery Input Voltage Range
Main step-up DC-DC Converter
`1.5V to 5.5V Adjustable Output Voltage
`Up to 90% Efficiency
`2.6A, 0.3Ω
Ω Internal Power Switch
Two Step-Down DC-DC Converters
`0.8V to 5.5V Adjustable Output Voltage
`94% Efficiency
`100% Duty Cycle
Step-up Charge Pump for Micro-Controller
Build-in 0.8V Voltage Detector
Up to 1.4MHz Switching Frequency
1μ
μA Supply Current in Shutdown Mode
Programmable Soft Start Function
Independent Enable Pin (CH1, CH2, CH3)
External Compensation Network (CH1, CH2, CH3)
Short Circuit Protection (CH1, CH2, CH3)
Over Voltage Protection (CH2)
32-Lead VQFN Package
RoHS Compliant and 100% Lead (Pb)-Free
VQFN-32L 5x5
DS9901-12 August 2007
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1
RT9901
Preliminary
Typical Application Circuit
1-cell Li+ Battery 3.4V to 4.2V
V BAT
C13 C14
10μF 10μF
1μF
C15
0.1μF
9
32
D1
SS0520
V BAT
C4
10μF
IGBT Driver
5V/50mA
R3
680k
C7 to C8
10μF x 2
C5
C6
D2
SS0520
1nF
14
15
29
30
C10
1nF
LBO
CPFB
LBI
EN3
R6 30k
27 COMP2
R7 30k
1 COMP3
LX2
C16
100pF
Low Battery
Warning Output
(Open Drain)
R11
10
4
21
22
V BAT
L3
4.7μH
C23
100pF
FB2
6
10μF x 4
8
23
VDD2
24
12 COMP1
C12
1nF
10uF
R12
EN2
5 SS
GND
2
C21 to C24
R9
680k
R10
130k
RT9901
CX
D3
SS0520
5V/500mA
RT9701CB
5
VIN
VOUT
EN
VOUT 1
17
11
R5 20k
C11
1nF
VDDC
25 ENM
26 EN1
Chip Enable
C9
4.7nF
VDD1
FB1
22nF
13
R4
130k
FB3
4
Chip Enable
20 16
C25 to C26
10μF x 2
3.3V/500mA
R13
470k
28
GND
R2
220k
C3
100pF
PGND1
C17 to C20
10μF x 4
R1
200k
LX1 18
19
3 LX3
PGND2
1.5V/500mA
3
VDDM
L1
4.7μH
PGND3
C1 to C2
10μF x 2
RT
V BAT
2 VDD3
L2
4.7μH
C27 to C30
10μF x 4
R14
150k
7, 31,
Exposed Pad (33)
R8
Figure 1. Typical Application Circuit from 1-cell Li+ Battery
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DS9901-12 August 2007
RT9901
Preliminary
2-AA Battery 2.0V to 3.4V
C12
1μF
C1 to C2
10μF x 2
L1
4.7μH
1.5V/300mA
C3
100pF
V BAT
D1
SS0520
32
FB3
14
R3
47k
C7
10μF
D2
C5 SS0520 10nF
1nF
R4
15k
Chip Enable
15
13
30
R5 20k
R6 30k
R7 30k
C9
1nF
LBI
27
COMP1
COMP2
C11
1nF
6
8
R11
10
I/O 3.3V/500mA
C17 to C20
10μF x 4
Low Battery
Warning Output
(Open Drain)
V BAT
4
3.3V
C21 to C22
10μF x 2
L3
4.7μH
C14
100pF
1 COMP3
5 SS
C13
100pF
R10
150k
21
LX2
22
FB2
C10
1nF
R9
470k
23
VDD2
24
EN3
12
C15 to C16
10μF x 2
R12
EN2
RT
C8
4.7nF
LBO
CPFB
25 ENM
26 EN1
29
11
RT9901
CX
V BAT
D3
SS0520
20 16
2.5V/300mA
R13
470k
28
GND
μC standby
3.3V/1mA
FB1
L2
4.7μH
17
VDDC
C4
10μF
C6
VDD1
PGND1
R2
220k
LX1 18
19
3 LX3
PGND2
C27 to C30
10μF x 4
VDD3
PGND3
R1
200k
VDDM
9
2
V BAT
C23 to C26
10μF x 4
R14
220k
7, 31,
Exposed Pad (33)
R8
Figure 2. Typical Application Circuit from 2-AA Battery Supply
DS9901-12 August 2007
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3
RT9901
Preliminary
Function Block Diagram
VDDM
VDDC
CX
CPFB
ENM
EN1
VDD1
LX1
EN
CH1
Current-MODE
Asynchronous
Step-Up
PWM
CH4
Charge Pump
LBO
PGND1
Boost
EN
Voltage Dector
COMP1
FB1
LBI
Soft-Start
OSC
SS
LX2
PGND2
Buck2
PWM
OSC
RT
EN2
VDD2
CH2
Current-MODE
Synchronous
Step-Down
PWM
Thermal
Shutdown
COMP2
FB2
EN3
VDD3
CH3
Current-MODE
Synchronous
Step-Down
PWM
LX3
PGND3
Buck3
GND
ENM
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EN1
EN2
EN3
COMP3
FB3
GND
Charge
CH1+Voltage
Pump
Detector
CH2
CH3
0
X
X
X
Off
Off
Off
Off
1
0
0
0
On
Off
Off
Off
1
1
0
0
On
On
Off
Off
1
1
1
0
On
On
On
Off
1
1
1
1
On
On
On
On
DS9901-12 August 2007
RT9901
Preliminary
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
COMP3
CH3 feedback compensation pin.
2
VDD3
3
LX3
CH3 power input pin.
CH3 switch node. Drains of the internal P-channel and N-MOSFET switches.
Connect an inductor to LX3 pins together as close as possible.
4
PGND3
5
SS
6
RT
7
GND
Analog Ground
8
LBO
Voltage detector output.
9
VDDM
Device input power pin.
10
LBI
Voltage detector feedback input.
11
FB1
CH1 feedback input pin.
12
COMP1
CH1 feedback compensation pin.
13
CPFB
Charge pump feedback pin.
14
VDDC
Charge pump power input pin.
15
CX
Charge pump external driver pin.
16
PGND1
Power ground for CH1.
17
VDD1
CH1 power input pin. Connect output of Boost to this pin.
LX1
CH1 switch node. Connect an inductor to LX1 pins together as close as possible.
PGND2
Power ground for CH2.
CH2 switch node. Drains of the internal P-channel and N-MOSFET switches.
Connect an inductor to LX2 pins together as close as possible.
18, 19
20
Power ground for CH3.
Sets the soft start interval of the converter. Connect a capacitor from this pin to
ground.
Frequency setting resistor connection pin. Frequency is 500KHz if RT pin not
connected
21, 22
LX2
23, 24
VDD2
25
ENM
26
EN1
27
COMP2
CH2 feedback compensation pin.
28
FB2
29
EN2
30
EN3
CH2 feedback input.
CH2 enable input. Tie this pin higher than 1.3V to enable CH2. Tie below 0.4V to
turn off the CH2.
CH3 enable input. Tie this pin higher than 1.3V to enable CH3. Tie below 0.4V to
turn off the CH3.
31
GND
Analog ground.
32
FB3
CH3 feedback input.
Exposed Pad (33) GND
DS9901-12 August 2007
CH2 power input pin.
Whole device control pin. Tie this pin higher than 1.3V to enable the device. Tie
below 0.4V to turn off the device.
CH1 enable input. Tie this pin higher than 1.3V to enable CH1. Tie below 0.4V to
turn off the CH1.
The exposed pad must be soldered to a large PCB and connected to GND for
maximum power dissipation.
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RT9901
Preliminary
Absolute Maximum Ratings
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Supply Input Voltage (VDDM, VDD1, VDD2,VDD3,VDDC) ----------------------------------------------------- −0.3 to 7V
LX1 Pin Switch Voltage ----------------------------------------------------------------------------------------- −0.3V to 7V
LX2 Pin Switch Voltage ----------------------------------------------------------------------------------------- −0.3V to (VDD2 + 0.3V)
LX3 Pin Switch Voltage ----------------------------------------------------------------------------------------- −0.3V to (VDD3 + 0.3V)
CX Pin Switch Voltage ------------------------------------------------------------------------------------------ −0.3V to (VDDC + 0.3V)
Other I/O Pin Voltage -------------------------------------------------------------------------------------------- −0.3V to (VDDM + 0.3V)
Package Thermal Resistance
VQFN-32L 5x5, θJA ----------------------------------------------------------------------------------------------- 34°C/W
Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------------- 260°C
Operation Temperature Range --------------------------------------------------------------------------------- −40°C to 85°C
Junction Temperature Range ----------------------------------------------------------------------------------- 0°C to 125°C
Storage Temperature Range ----------------------------------------------------------------------------------- −65°C to 150°C
ESD Susceptibility
HBM (Human Body Mode) ------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) --------------------------------------------------------------------------------------------- 200V
Electrical Characteristics
(VDDM =3.3V, TA = 25°C, Unless Otherwise specification)
Parameter
Symbol
Test Condition
Min
Typ
Max
Units
--
1.5
--
V
2.4
--
5.5
V
5.5
V
Supply Voltage
Minimum Startup Voltage (Boost)
VST
VDDM Operating Voltage
VVDDM
VDDM Pin Voltage
VVDD1
VDD1, VDD2, VDD3 Pin
VVDD2,
Voltage
VDD1, VDD2, VDD3 Operating
Voltage
Boost loading < 1mA
1.5
VVDD3
VDDM Over Voltage Protection
--
6.5
--
V
--
0.01
1
μA
--
30
42
μA
--
250
350
μA
--
250
350
μA
--
250
350
μA
Supply Current
Shutdown Supply Current
IOFF
VENM pin=0V
VVDDM = 3.3V, VENM = 3.3V,
Charge Pump Current
IVDDM
VEN1 = 0V, VEN2 = 0V,
VEN3 = 0V
VVDDM = 3.3V,
CH1 DC/DC Converter + Voltage
Detector Supply Current
IVDDM
VFB1 = 0.9V
VENM = 3.3V, VEN1 = 3.3V,
VEN2 = 0V, VEN3 = 0V
VVDDM = 3.3V,
CH2 DC/DC Converter Supply
Current
IVDDM
VFB2 = 0.9V
VENM = 3.3V, VEN1 = 0V,
VEN2 = 3.3V, VEN3 = 0V
VVDDM = 3.3V,
CH3 DC/DC Converter Supply
Current
IVDDM
VFB3 = 0.9V
VENM = 3.3V, VEN1 = 0V,
VEN2 = 0V, VEN3 = 3.3V
To be continued
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6
DS9901-12 August 2007
RT9901
Preliminary
Parameter
Symbol
Test Condition
Min
Typ
Max
Units
Oscillator
Operation Frequency Range
FOSC
475
550
625
kHz
CH1 Maximum Duty Cycle
DMAX1
RT Open
--
85
90
%
CH2 Maximum Duty Cycle
DMAX2
--
--
100
%
CH3 Maximum Duty Cycle
DMAX3
--
--
100
%
0.788
0.8
0.812
V
0.78
0.8
0.82
V
--
--
12
mV
GM
--
0.2
--
ms
Compensation Source Current
--
22
--
μA
Compensation Sink Current
--
22
--
μA
N-MOSFET
--
300
400
mΩ
VVDD1 = 3.3V
2
2.6
3
A
N-MOSFET, VVDD2 = 3.3V
--
350
450
mΩ
P-MOSFET, VVDD2 = 3.3V
--
350
450
mΩ
1.3
1.5
1.9
A
N-MOSFET, VVDD3 = 3.3V
--
350
450
mΩ
P-MOSFET, VVDD3 = 3.3V
--
350
450
mΩ
VVDD3 = 3.3V
1.3
1.5
1.9
A
VLBI (Falling)
0.75
0.77
0.79
V
VLBI (Rising)
0.79
0.81
0.83
V
3
5
--
mA
UVP Threshold Voltage @FB2, FB3
0.3
0.4
0.5
V
Over Voltage Protection @FB2
0.95
1
--
V
VVDDM = 3.3V
--
0.8
1.3
V
VVDDM = 3.3V
0.4
0.8
--
V
140
180
--
°C
--
10
--
°C
Feedback Voltage (CH1, CH2, CH3, CH4)
Feedback Voltage
Feedback Voltage (Charge Pump)
VFB
CH1, CH2, CH3
VCPFB
CH4
Feedback Voltage
︱ΔVFB︱
CH1, CH2, CH3, CH4
3.0V < VDDM < 5.5V
Error Amplifier
Power Switch
CH1 On Resistance of MOSFET
RDS(ON)
CH1 Current Limitation
CH2 On Resistance of MOSFET
RDS(ON)
CH2 Current Limitation
CH3 On Resistance of MOSFET
VVDD2 = 3.3V
RDS(ON)
CH3 Current Limitation
Voltage Detector
Feedback Voltage for Voltage
detector
Feedback Voltage for Voltage
detector
LBO pin Sink Current
VLBO= 1V
UVP (CH2, CH3) & Over Voltage Protection (CH2)
Control
ENM, EN1, EN2, EN3 Input High
Level Threshold
ENM, EN1, EN2, EN3 Input Low
Level Threshold
Thermal Protection
Thermal Shutdown
TSD
Thermal Shutdown Hysteresis
ΔTSD
DS9901-12 August 2007
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7
RT9901
Preliminary
Typical Operating Characteristics
Oscillator Ferquency vs. RRT
1800
0.806
1600
Oscillator Frequecny (kHz)
Reference Voltage (V)
Reference Voltage vs. Temperature
0.808
0.804
0.802
0.8
0.798
0.796
0.794
1400
1200
1000
800
600
400
200
0.792
0
-50
-30
-10
10
30
50
70
90
0
100
200
300
Temperature (°C)
500
600
RRT (kΩ)
Boost Output Voltage vs. VDD1 Voltage
Boost Efficiency vs. Output Current
3.345
100
VBAT = 2.5V, VDDM = 3.3V, IOUT = 250mA
VOUT = 3.3V
2.5V
80
2V
1.8V
70
60
Output Voltage (V)
3.34
VIN
3V
90
Efficiency (%)
400
3.335
3.33
3.325
3.32
3.315
3.31
Boost
3.305
50
1
10
100
1.5
1000
Output Current (mA)
3
3.5
4
4.5
5
5.5
Boost Load Transient Response
Output Voltage
Deviation
(100mV/Div)
VBAT = 2.5V, VDD1 = 3.3V, IOUT = 250mA
3.33
3.328
3.326
3.324
3.322
Load Current
(200mA/Div)
Output Voltage (V)
2.5
VDD1 Voltage (V)
Boost Output Voltage vs. VDDM Voltage
3.332
2
3.32
3.318
3.316
2.4
2.8
3.2
3.6
4
4.4
4.8
5.2
5.6
VIN = 1.8V, VOUT = 3.3V, @IOUT = 100mA to 400mA
Time (1ms/Div)
VDDM Voltage (V)
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DS9901-12 August 2007
Preliminary
Boost Load Transient Response
Load Current
(200mA/Div)
VIN = 2V, VOUT = 3.3V, @IOUT = 100mA to 400mA
VIN = 2.5V, VOUT = 3.3V, @IOUT = 100mA to 400mA
Time (1ms/Div)
Time (1ms/Div)
Boost Load Transient Response
Boost LX & Output Ripple
VIN = 1.8V, VOUT = 3.3V, @IOUT = 100mA
VIN = 3V, VOUT = 3.3V, @IOUT = 100mA to 400mA
Output Ripple
(10mV/Div)
LX1
(2V/Div)
Output Voltage
Deviation
(100mV/Div)
Load Current
(200mA/Div)
Output Voltage
Deviation
(100mV/Div)
Output Voltage
Deviation
(100mV/Div)
Boost Load Transient Response
Load Current
(200mA/Div)
RT9901
Time (1ms/Div)
Time (1us/Div)
Boost LX & Output Ripple
Boost LX & Output Ripple
Output Ripple
(10mV/Div)
Output Ripple
(10mV/Div)
Time (1us/Div)
DS9901-12 August 2007
VIN = 2.5V, VOUT = 3.3V, @IOUT = 100mA
LX1
(2V/Div)
LX1
(2V/Div)
VIN = 1.8V, VOUT = 3.3V, @IOUT = 300mA
Time (1us/Div)
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RT9901
Preliminary
Boost LX & Output Ripple
Boost LX & Output Ripple
VIN = 3V, VOUT = 3.3V, @IOUT = 100mA
Output Ripple
(10mV/Div)
Output Ripple
(10mV/Div)
LX1
(2V/Div)
LX1
(2V/Div)
VIN = 2.5V, VOUT = 3.3V, @IOUT = 400mA
Time (1us/Div)
Time (1us/Div)
Buck2 Efficiency vs. Output Current
Boost LX & Output Ripple
100
VIN = 3V, VOUT = 3.3V, @IOUT = 400mA
VOUT = 1.5V
VIN = 2.2V
Output Ripple
(10mV/Div)
LX1
(2V/Div)
Efficiency (%)
90
80
VIN = 4.5V
VIN = 2.5V
VIN = 3V
VIN = 3.8V
70
60
50
Time (1us/Div)
1
10
100
1000
Output Current (mA)
Buck2 Efficiency vs. Output Current
100
Buck2 Efficiency vs. Output Current
100
VOUT = 1.8V
VIN = 2.5V
90
VIN = 4.5
80
80
Efficiency (%)
Efficiency (%)
VOUT = 2.5V
90
VIN = 3V
VIN = 4.5 VIN = 3.8V
70
70
60
VIN = 3.8V
50
VIN = 3V
60
40
30
50
1
10
100
Output Current (mA)
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10
1000
1
10
100
1000
Output Current (mA)
DS9901-12 August 2007
RT9901
Preliminary
Buck2 Output Voltage vs. VDD2 Voltage
Buck2 Output Voltage vs. VDDM Voltage
1.82
1.82
VDD2 = 3.3V, IOUT = 250mA
1.818
1.816
1.816
Output Voltage (V)
Output Voltage (V)
VBAT = VDDM = 3.3V, IOUT = 250mA
1.818
1.814
1.812
1.81
1.808
1.814
1.812
1.81
1.808
1.806
1.806
1.804
1.804
2
2.5
3
3.5
4
2
4.5
3.5
4
4.5
5
5.5
VDDM Voltage (V)
Buck2 Load Transient Response
Buck2 Load Transient Response
6
@IOUT = 100mA to 400mA
VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
Load Current
(200mA/Div)
Output Voltage
Deviation
(100mV/Div)
Output Voltage
Deviation
(100mV/Div)
Load Current
(200mA/Div)
3
VDD2 Voltage (V)
@IOUT = 100mA to 400mA
Time (1ms/Div)
VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
DS9901-12 August 2007
Output Voltage
Deviation
(100mV/Div)
Buck2 Load Transient Response
Load Current
(200mA/Div)
Output Voltage
Deviation
(100mV/Div)
@IOUT = 100mA to 400mA
VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
Buck2 Load Transient Response
Load Current
(200mA/Div)
2.5
@IOUT = 100mA to 400mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
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11
RT9901
Preliminary
Buck2 LX & Output Ripple
Buck2 LX & Output Ripple
@IOUT = 250mA
Time (500ns/Div)
Buck2 LX & Output Ripple
Buck2 LX & Output Ripple
LX2
(2V/Div)
Output Ripple
(10mV/Div)
@IOUT = 250mA
VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V
@IOUT = 500mA
VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
Buck2 LX & Output Ripple
Buck2 LX & Output Ripple
LX2
(2V/Div)
@IOUT = 250mA
VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
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12
Output Ripple
(10mV/Div)
Output Ripple
(10mV/Div)
VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
LX2
(2V/Div)
Output Ripple
(10mV/Div)
Output Ripple
(10mV/Div)
VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
LX2
(2V/Div)
Output Ripple
(10mV/Div)
LX2
(2V/Div)
LX2
(2V/Div)
@IOUT = 500mA
@IOUT = 500mA
VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
DS9901-12 August 2007
RT9901
Preliminary
Buck2 LX & Output Ripple
Output Ripple
(10mV/Div)
Output Ripple
(10mV/Div)
LX2
(2V/Div)
LX2
(2V/Div)
Buck2 LX & Output Ripple
@IOUT = 250mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
@IOUT = 500mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
Buck3 Efficiency vs. Output Current
Buck3 Efficiency vs. Output Current
100
100
VOUT = 1.5V
VOUT = 1.8V
VIN = 2.2V
90
80
Efficiency (%)
Efficiency (%)
90
VIN = 4.5V
VIN = 3V
VIN = 3.8V
70
VIN = 2.5V
80
VIN = 4.5V
VIN = 3.8V VIN = 3V
70
60
60
50
50
1
10
100
1
1000
10
100
1000
Output Current (mA)
Output Current (mA)
Buck3 Output Voltage vs. VDD3 Voltage
Buck3 Efficiency vs. Output Current
1.806
100
VBAT = VDDM = 3.3V, IOUT = 250mA
VOUT = 2.5V
1.804
90
VIN = 4.5V
Output Voltage (V)
80
Efficiency (%)
VIN = 2.5V
70
VIN = 3.8V
60
50
VIN = 3V
40
1.802
1.8
1.798
1.796
1.794
1.792
1.79
30
1
10
100
Output Current (mA)
DS9901-12 August 2007
1000
2
2.5
3
3.5
4
4.5
VDD3 Voltage (V)
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13
RT9901
Preliminary
Buck3 Output Voltage vs. VDDM Voltage
Buck3 Load Transient Response
1.806
Output Voltage
Deviation
(100mV/Div)
VDD3 = 3.3V, IOUT = 250mA
1.802
1.8
@IOUT = 100mA to 400mA
1.798
1.796
Load Current
(200mA/Div)
Output Voltage (V)
1.804
1.794
1.792
1.79
2
2.5
3
3.5
4
4.5
5
5.5
VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
6
Time (1ms/Div)
VDDM Voltage (V)
VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V
Load Current
(200mA/Div)
Load Current
(200mA/Div)
Output Voltage
Deviation
(100mV/Div)
@IOUT = 100mA to 400mA
Buck3 Load Transient Response
Output Voltage
Deviation
(100mV/Div)
Buck3 Load Transient Response
VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
Time (1ms/Div)
Buck3 Load Transient Response
Buck3 LX & Output Ripple
@IOUT = 250mA
VDD3 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (1ms/Div)
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14
Output Ripple
(10mV/Div)
LX3
(2V/Div)
Output Voltage
Deviation
(100mV/Div)
@IOUT = 100mA to 400mA
Load Current
(200mA/Div)
@IOUT = 100mA to 400mA
VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
DS9901-12 August 2007
RT9901
Preliminary
Buck3 LX & Output Ripple
Buck3 LX & Output Ripple
Output Ripple
(10mV/Div)
VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V
LX3
Output Ripple
(10mV/Div) (2V/Div)
@IOUT = 250mA
LX3
(2V/Div)
@IOUT = 500mA
Time (500ns/Div)
Time (500ns/Div)
Buck3 LX & Output Ripple
Buck3 LX & Output Ripple
@IOUT = 500mA
@IOUT = 250mA
VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V
LX3
Output Ripple
(10mV/Div) (2V/Div)
LX3
Output Ripple
(10mV/Div) (2V/Div)
VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V
VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Time (500ns/Div)
Buck3 LX & Output Ripple
Buck3 LX & Output Ripple
VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
DS9901-12 August 2007
LX3
Output Ripple
(10mV/Div) (2V/Div)
Output Ripple
(10mV/Div)
LX3
(2V/Div)
@IOUT = 500mA
@IOUT = 250mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
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15
RT9901
Preliminary
Buck3 LX & Output Ripple
Charge Pump CX & Output Ripple
@IOUT = 1mA
VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V
Time (500ns/Div)
Output Ripple Charge Pump
(5mV/Div)
(2V/Div)
Output Ripple
(10mV/Div)
LX3
(2V/Div)
@IOUT = 500mA
VIN = 2V, VDDM = 3.3V, VOUT = 3.3V
Time (5us/Div)
Charge Pump CX & Output Ripple
Output Ripple Charge Pump
(5mV/Div)
(2V/Div)
@IOUT = 1mA
VIN = 2.5V, VDDM = 3.3V, VOUT = 3.3V
Time (25us/Div)
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16
DS9901-12 August 2007
Preliminary
RT9901
Application Information
The RT9901 is a four-channel DC/DC converter with one
voltage detector for digital still cameras and other handheld device. The four channels DC/DC converters are as
follows:
CH1: Step-up, asynchronous current mode DC/DC
converter with an internal power MOSFET, current limit
protection and high efficiency control for wide loading
range
CH2: Step-down, synchronous current mode DC/DC
converter with internal power MOSFETs, current limit,
short-circuit , over voltage protection and high efficiency
control for wide loading range.
CH3: Step-down, synchronous current mode DC/DC
converter with internal power MOSFETs, current limit,
short-circuit protection and high efficiency control for wide
loading range.
CH4: Charge pump DC/DC converter.
Soft-Start
CH1, CH2 and CH3 can be soft-started individually every
time when the channel is enabled. Soft-start is achieved
by ramping up the voltage reference of each channel's
input of error amplifier. Adding a capacitor on SS pin to
ground sets the ramping up speed of each voltage
reference. Triangle wave will be appeared on SS pin,
which provides a clock base for soft-start.
The soft-start timing would be setted by following formular.
TSS = 10 x
CSS
(ms)
1nF
Oscillator
The internal oscillator synchronizes CH1, CH2 and CH3
PWM operation frequency. The operation frequency is
set by a resistor between RT pin to ground, ranging from
550kHz to 1.4MHz.
Step-up (Boost) DC/DC Converter (CH1)
The step-up channel (CH1) is designed as current-mode
DC/DC PWM converters with built-in internal power MOS
and external Schottky diode. Output voltage is regulated
and adjustable up to 5.5V. This channel typically supplies
3.3V for main system power.
DS9901-12 August 2007
At light load, efficiency is enhanced by pulse-skipping
mode. In this mode, the NMOS turns on by a constant
pulse width. As loading increased, the converter operates
at constant frequency PWM mode. The max. duty of the
constant frequency is 80% for the boost to prevent high
input current drawn from input.
Protection
Current limit
The current of NMOS is sensed cycle by cycle to prevent
over current. If the current is higher than 2.6A (typical),
then the NMOS is off . This state is latched and then
reset automatically at next clock cycle.
Under Voltage
The status of under voltage is decided by comparing FB1
voltage with 0.4V. This function is enabled after soft start
finishes. If the FB1 voltage is less than 0.4V, then the
NMOS will be turned off immediately. And this state is
latched. After a dummy count period, the controller begins
a re-soft-start procedure.
If the status of under voltage remains after 4 successive
times of soft-start, then CH1 is latched.
Over Voltage
The over voltage protection is used when the output of
CH1 supplies the power of the main chip. If the output
voltage of CH1 is over 6.5V, the main chip is shutdown
and the NMOS is kept off.
Step-Down (Buck) DC/DC Converter (CH2, CH3)
The step-down channels (CH2, CH3) are designed as
synchronous current-mode DC/DC PWM converters.
Output voltage is regulated and adjustable down to 0.8V.
The internal synchronous power switches eliminate the
typical Schottky free wheeling diode and improve
efficiency.
At light load, efficiency is enhanced by pulse-skipping
mode. In this mode, the high-side PMOS turns on by a
constant pulse width. As loading increased, the converter
operates at constant frequency PWM mode. While the
input voltage is close to output voltage, the converter
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17
RT9901
Preliminary
enters low dropout mode. Duty could be as long as 100%
to extend battery life.
Protection
Current limit (CH2, CH3)
The current of high-side PMOS is sensed cycle by cycle
to prevent over current. If the current is higher than 1.5A
(typical), then the high-side PMOS is off and the low-side
NMOS is on. This state is latched and then reset
automatically at next clock cycle.
The maximum output current can be determined by Cpump
and C OUT ration. This equation would describe the
relationship.
IMAX = 2 x (VDDC-VF) x Cpump x Fpump
z
VF : Schottky diode forward voltage
z
Fpump : Charge pump maximum frequency is 500kHz
Recommand Cpump ≤ 0.1μF.
The status of under voltage is decided by comparing FB2
(or FB3) voltage with 0.4V. This function is enabled after
soft start finishes. If the FB2 (or FB3) voltage is less than
0.4V, then the high/low-side Power MOS are turned off
immediately. And this state is latched. After a dummy
count period, the CH2 (or CH3) begins a soft-start
procedure.
However, if the status of under voltage remains after 3
successive times of soft-start, then CH2 (or CH3) is
latched.
UV remain after 3
How to reset?
successive soft-start
CH2 CH2 is latched, and whole Toggle ENM
IC is shut down
CH3 CH3 is latched
Toggle EN3 or ENM
Over Voltage Protection (CH2)
Over voltage protection (OVP) is used to protect the
external parts connected to the output of CH2. If the FB2
voltage is higher than 1V, the high-side PMOS is off and
low-side NMOS is on. This status is latched and could be
reset by toggling ENM.
VBAT
VDDC
Under Voltage (CH2, CH3)
CX
Cpump
R1
CPFB
GND
R2
CX
COUT
Reference
The chip has an internal 0.8V reference voltage, which is
the inputs of the error amplifiers of the CH1, CH2, and
CH3 to compare the difference of feedback voltage. The
reference voltage can be set up stably when the supplied
power (VDDM) is above 1.5V, and EN1 (or EN2, EN3)
goes high.
Thermal Protection
Thermal protection function is integrated in the chip. When
the chip temperature is higher than 178 degree C, the
controllers of CH1, CH2, and CH3 are shutdown. 10
degree C is the hysteresis range of temperature to prevent
unstable operation when the thermal protection happens.
When the thermal protection is relieved, the chip operates
well again.
Charge Pump DC/DC converter
This is a low quiescent charge pump DC/DC converter,
which is enabled by ENM. Add a capacitor CX (~1nF)
between charge pump VOUT and CPFB to speed up charge
pump response time. Output ripple can be easily
suppressed by increasing the capacitance ratio of COUT
and Cpump. This charge pump DC/DC converter can
apply to μC stanby power or the gate driver power of IGBT
for photoflash, etc.
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18
DS9901-12 August 2007
RT9901
Preliminary
Outline Dimension
D2
D
SEE DETAIL A
L
1
E
E2
e
b
1
1
2
2
A
A1
A3
DETAIL A
Pin #1 ID and Tie Bar Mark Options
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
4.950
5.050
0.195
0.199
D2
3.400
3.750
0.134
0.148
E
4.950
5.050
0.195
0.199
E2
3.400
3.750
0.134
0.148
e
L
0.500
0.350
0.020
0.450
0.014
0.018
V-Type 32L QFN 5x5 Package
Richtek Technology Corporation
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
8F, No. 137, Lane 235, Paochiao Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)89191466 Fax: (8862)89191465
Email: [email protected]
DS9901-12 August 2007
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19