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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Features
n Efficiency up to 96% n Only 40A (Typ. per Channel) Quiescent Current n Output Current: Up to 1A per Channel n Internal Synchronous Rectifier n 1.5MHz Switching Frequency n Soft Start n Under-Voltage Lockout n Short Circuit Protection n Thermal Shutdown n Small 12L WDFN3x3 Package n Pb-Free Package and RoHS Compliant
General Description
The PAM2306 is a dual step-down current-mode, DC-DC converter. At heavy load, the constantfrequency PWM control performs excellent stability and transient response. To ensure the longest battery life in portable applications, the PA M 2 3 0 6 p r o v i d e s a p o w e r - s a v i n g P u l s e Skipping Modulation (PSM) mode to reduce quiescent current under light load operation. The PAM2306 supports a range of input voltages from 2.5V to 5.5V, allowing the use of a single Li+/Li-polymer cell, multiple Alkaline/NiMH cell, USB, and other standard power sources. The dual output voltages are available for 3.3V, 2.8V, 2.5V, 1.8V, 1.5V, 1.2V or adjustable. All versions employ internal power switch and synchronous rectifier for to minimize external part count and realize high efficiency. During shutdown, the input is disconnected from the output and the shutdown current is less than 0.1 A. Other key features include under-voltage lockout to prevent deep battery discharge.
Applications
n n n n n
Cellular Phone Portable Electronics Personal Information Appliances Wireless and DSL Modems MP3 Players
Typical Application
L2 C OUT2 10F V OUT2 V IN2 1 VIN2 CIN2 4 7F R12 2 3 4 LX2 GND FB1 PAM2306 EN2 12 NC2 11 FB2 10 GND LX1 9 8 R22 C IN1 4. F 7 V IN1 R21 C FW2 100 pF
5 NC1 CFw1 100 pF V OUT1 C OUT1 10F R11 6 EN1 L1
VIN1 7
VOUTx = VREF 1 + Rx1 Rx2
(
)
Figure 1. Adjustable Voltage Regulator
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Typical Application
L2 V OUT2 V IN2 1 VIN2 C IN2 4. 7F 2 LX2 PAM2306 EN2 12 NC2 11 FB2 10 GND LX1 VIN1 L1 V OUT1 C OUT1 10F 9 8 7 C IN1 4. 7F V IN1 C OUT2 10 F
3 GND 4 FB1
5 NC1 6 EN1
VOUTx = 1. 2V,1. 5V,1.8V,2. 2.8V or 3. 5V, 3V
Figure 2. Fixed Voltage Regulator
Block Diagram
VINx
OSC
FBx
FREQ SHIFT
+
-++
1 . 5M OSC
SLOPE COMP
PWM COMP
IAMP
+ -
SQ
EA
R1 R2
COMP VIN
SWITCHING RQ LOGIC AND RS LATCH BLANKING CIRCUIT
MAIN SWITCH ( PCH )
ANTI SHOOT THRU
LXx
SYNCHRONOUS RECTIFIER ( NCH )
ENx
0 . 6VREF
SHUTDOWN
IRCMP
+ -
GND
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Pin Configuration and Marking Information
TOP VIEW
WDFN-12L 3x3
VIN2 LX2 GND
1 2 3
2306v 1v 2 XXXYW
12 11 10 9 8 7 GND
EN2 NC2 FB2 GND LX1 VIN1
FB1 4 NC1 5 EN1 6
v 1: Output Voltage 1 v 2: Output Voltage 2 (refer to "Ordering Information") X: Internal Code Y: Year W: Week
(Exposed Pad)
Pin No. 1 2 3,9, Exposed Pad 4 5,11 6 7 8 10 12
Pin Name VIN2 LX2 GND FB1 NC1,NC2 EN1 VIN1 LX1 FB2 EN2 Power Input of Channel 2. Pin for Switching of Channel 2.
Pin Function
Ground.The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Feedback of Channel 1. No Connection Chip Enable of Channel 1 (Active High).VEN1VIN1. Power I put of Channel 1. n Pin for Switching of Channel 1. Feedback of Channel 2. Chip Enable of Channel 2 (Active High). VEN2VIN2.
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Absolute Maximum Ratings
These are stress ratings only and functional operation is not implied . Exposure to absolute maximum ratings for prolonged time periods may affect device reliability . All voltages are with respect to ground . Input Voltage................................. - 0.3V to 6.5V En1, Fb1, Lx1, En2, Fb2 and LX2 Pin Voltage........ - 0 . 3V to ( V IN + 0 . 3V ) Junction Temperature................................150C Storage Temperature Range....... - 65C to 150C Soldering Temperature.....................260C , 10sec
Recommended Operating Conditions
Supply Voltage...............................2.5V to 5.5V Ambient Temperature Range......... - 40 C to 85 C Junction Temperature Range.........-40C to 125 C
Thermal Information
Parameter
Thermal Resistance (Junction to ambient) Thermal Resistance (Junction to case) Power Dissipation
Symbol
JA JC PD
Package
WDFN 3x3-12 WDFN 3x3-12 WDFN 3x3-12
Maximum
60 8.5 1.66
Unit
C/W C/W W
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Electrical Characteristic
T A=25 OC, V IN=3.6V, V O=1.8V, C IN=10F, C O=10F, L=2.2H, unless otherwise noted.
PARAMETER Input Voltage Range Regulated Feedback Voltage Reference Voltage Line Regulation Regulated Output Voltage Accuary Peak Inductor Current Output Voltage Line Regulation Output Voltage Load Regulation Quiescent Current (per channel) Shutdown Current (per channel) Oscillator Frequency Drain-Source On-State Resistance SW Leakage Current (per channel) High Efficiency EN Threshold High EN Threshold Low EN Leakage Current Over Temperature Protection OTP Hysteresis SYMBOL V IN VFB VFB VO IPK LNR LDR IQ ISD fOS C RDS(ON) ILSW V EH VE L IEN OTP OTH 0.01 150 30 1.5 0.3 IO = 100mA V IN =3V,V FB = 0.5V or VO=90% V IN = 2.5V to 5V, IO =10mA IO=1mA to 1A No load V EN = 0V V O = 100% V FB = 0V or VO = 0V IDS=100mA P MOSFET N MOSFET 1.2 -3 1.5 0.2 0.5 40 0.1 1.5 500 0.3 0.35 0.01 96 0.45 0.5 1 0.5 1.5 70 1 1.8 Test Conditions MIN 2.5 0.588 0.6 0.3 +3 TYP MAX 5.5 0.612 UNITS V V %/V % A %/V % A A MHz kHz A % V V A C C
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Typical Performance Characteristics
T A=25 C , C IN=10 F, C O=10 F, L=4.7 H, unless otherwise noted. Efficiency vs Output Current (Vo=1.2V) Efficiency vs Output Current (Vo=1.5V)
100 90 80 70 60 50 40 30 20 10 0
100 90
Efficiency(%)
Efficiency(%)
80 70 60 50 40 30 20
2.5V 3.6V 4.2V
Vin=3.6V Vin=4.2V Vin=5V
1
10
100
1000
1
10
100
1000
Output Current(mA)
Output Current(mA)
Efficiency vs Output Current ( Vo=1.8V )
100 90
100 90 80
Efficiency vs Output Current ( Vo=2.5V )
Efficiency(%)
80 70 60 50 40 30 20 1 10 100 Output Current(mA) 1000
2.5V 3.6V 4.2V
Efficiency(%)
70 60 50 40 30 20 1 10 100 1000 Output Current(mA)
3V 3.6V 4.2V
100 90
Efficiency vs Output Current (Vo=2.8V)
70 60 50 40 30 20 1 10 100 Output Current(mA)
3V 3.6V 4.2V
Efficiency(%)
Efficiency(%)
80
100 90 80 70 60 50 40 30 20 10 0
Eifficiency VS Output Current (Vo=3.3V)
Vin=3.6V Vin=4.2V Vin=5V
1000
1
10
100
1000
Output Current(mA)
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Typical Performance Characteristics
T A=25 C , C IN=10 F, C O=10 F, L=4.7 H, unless otherwise noted. Efficiency VS Input Voltage ( Vo=1.2V )
100 90
Efficiency(%)
Efficiency(%)
100 90 80 70 60 50
Io=10mA
Efficiency vs Input Voltage ( Vo=1.5V )
80 70 60 50 40 30 3 3.5 4 4.5 5 5.5 Input Voltage(V)
Io=100mA Io=800mA
10mA
40 30 2.5 3
100mA 800mA
3.5
4
4.5
5
5.5
Input Voltage(V)
Efficiency vs Input Voltage ( Vo=1.8V )
100 90
100 90
Efficiency vs Input Voltage ( Vo=2.5V )
Efficiency(%)
Efficiency(%)
80 70 60 50
10mA
80 70 60 50
10mA
40 30 2.5 3
100mA 800mA
40 30
100mA 800mA
3.5
4
4.5
5
5.5
3
3.5
4
4.5
5
5.5
Input Voltage(V)
Input Voltage(V)
100 90
Efficiency vs Input Voltage ( Vo=2.8V )
Eifficiency VS Input Voltage (Vo=3.3V)
100 90 80 70 60 50 40 30 20 10 0
Io=10mA Io=100mA Io=800mA
Efficiency(%)
70 60 50
10mA
40 30 3
100mA 800mA
Eifficiency(%)
80
3.5
4
4.5
5
5.5
3.5
3.75
4
4.25
4.5
4.75
5
5.25
5.5
Input Voltage(V)
Input Voltage(V)
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Typical Performance Characteristics
T A=25 C , C IN=10 F, C O=10 F,L=4.7 H, unless otherwise noted. Reference Voltage VS Input Voltage
0.602 0.600 0.598 0.596
Vfb(V)
Output Voltage VS Input Voltage
1.218 1.213
Output Voltage(V)
Vin=3.6V
1.208 1.203 1.198
Io=1mA
0.594 0.592 0.590 0.588 0.586 0.584 2 3 4 Input Voltage(V) 5 6
I=100mA I=600mA I=800mA
1.193 1.188 2.5 3
Io=500mA Io=1A
3.5
4
4.5
5
5.5
Input Voltage(V)
Reference Voltage VS Temperature
0.620
1.194 1.193
Output Voltage VS Temperature
Reference Voltage(V)
0.615 0.610 0.605 0.600 0.595 0.590 0 50 100 150 Tem perature(C)
Output Voltage(V)
1.192 1.191 1.19 1.189 1.188 20 40 60 80 100 120 140 Temperature(C)
Vo=1.2V Vin=3.6V Io=100mA
Reference Voltage VS Load Current
0.603 0.600
1.218
Output Voltage VS Load Current Vo=1.2V
1.213
Reference Voltage(V)
0.598 0.595 0.593 0.590 0.588 0.585 0.583 0.580 0 200 400 600 800 1000 Load Current(mA)
Vin=2.7V Vin=3.6V Vin=4.2V
Output Voltage(V)
1.208 1.203 1.198 1.193 1.188 0 100 200 300 400 500 600 700 800 900 1000 Load Current(mA)
Vin=2.7V Vin=3.6V Vin=4.2V Vin=5V
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Typical Performance Characteristics
T A=25 C, C IN=10 F, C O=10 F,L=4.7 H, unless otherwise noted. Dynamic Supply Current VS Input Voltage
50
O
Dynamic Supply Current VS Temperature
60
Dynamic Supply Current(uA)
Dynamic Supply Current(uA)
45 40 35 30 25 20 15 10 5 0
Vo=1.2V ILoad =0A
50 40 30
Vo=1.2V
20 10 0
Vin=3.6V ILoad=0A
2.5
3
3.5 4 4.5 Input Voltage(V)
5
5.5
40
60
80
100
120
140
Temperature(C)
R dson VS Input Voltage
0.4
Rdson VS Temperature
0.6
Vin=3.6V
0.35
RDS(ON)
Vin=3.6V
0.5 0.4
0.3 0.25 0.2 0.15 0.1 2 3 4 Input Voltage(V) 5 6
Rds(on)
0.3 0.2 0.1 0 20 70 Temperature(C) 120
Vin=4.2V Vin=3.6V Vin=2.7V
Oscillator Frequency VS Supply Voltage
1.8
1.58
Oscillator Frequency VS Temperature
Vin=3.6V
Oscillator Frequency(MHz)
1.56
Vin=3.6V
Oscillator Frequency(MHz)
1.7 1.6 1.5 1.4 1.3 1.2 2 3 4 Supply Voltage(V) 5
1.54
1.52
1.50 20 40 60 80 100 120 140 Temperature(C)
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Typical Performance Characteristics
T A=25 C ,C IN=10 F, C O=10 F,L=4.7 H, unless otherwise noted. Load Transient Io=0-500mA Vo=3.3V Vin=5V Load Transient Io=0-1A Vo=1.2V Vin=3.6V
Output Current
Output Current
Voltage Output
Voltage Output
Start-up from Shutdown Vo=1.8V,Vin=3.6V
Voltage Output
Enable
Inductor Current
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Application Information
The basic PAM2306 application circuit is shown in Page 1. External component selection is determined by the load requirement, selecting L first and then Cin and Cout. Inductor Selection For most applications, the value of the inductor will fall in the range of 1H to 4.7H. Its value is chosen based on the desired ripple current. Large value inductors lower ripple current and small value inductors result in higher ripple currents. Higher V IN or Vout also increases the ripple current as shown in equation 1. A reasonable starting point for setting ripple current is I L = 400mA (40% of 1A).
DIL = 1 ae VOUT o VOUT c 1/ f )(L ) VIN o ( e
The selection of Cout is driven by the required effective series resistance (ESR). Typically, once the ESR requirement for Cout has been met, the RMS current rating generally far exceeds the I RIPPLE(P-P) requirement. The output ripple Vout is determined by:
1o ae VVOUT @VIL c ESR+ / 8fCOUT o e
Where f = operating frequency, C OUT =output capacitance and I L = ripple current in the inductor. For a fixed output voltage, the output ripple is highest at maximum input voltage since I L increases with input voltage. Using Ceramic Input and Output Capacitors Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their high ripple current, high voltage rating and low ESR make them ideal for switching regulator applications. Using ceramic capacitors can achieve very low output ripple and small circuit size. When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formulations. These dielectrics have the best temperature and voltage charac teristics of all the ceramics for a given value and size. Thermal consideration Thermal protection limits power dissipation in the PAM2306. When the junction temperature exceeds 150C, the OTP (Over Temperature Protection) starts the thermal shutdown and turns the pass transistor off. The pass transistor resumes operation after the junction temperature drops below 120C. For continuous operation, the junction temperature should be maintained below 125C. The power dissipation is defined as:
PD =IO 2 VORDSONH + (VIN -VO )RDSONL VIN + (t SW FSIO +IQ )VIN
(1)
The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. Thus, a 1.4A rated inductor should be enough for most applications (1A + 400mA). For better efficiency, choose a low DC-resis tance inductor.
Vo L 1.2V 2.2H 1.5V 2.2H 1.8V 2.2H 2.5V 4.7H 3.3V 4.7H
C IN and C OUT Selection In continuous mode, the source current of the top MOSFET is a square wave of duty cycle Vout/Vin. To prevent large voltage transients, a low ESR input capacitor sized for the maximum RMS current must be used. The maximum RMS capacitor current is given by:
e VOUT (VIN - VOUT )u u CIN required IRMS @ IOMAX e VIN
1 2
This formula has a maximum at V IN =2Vout, w h e r e I RMS= I OUT/ 2 . T h i s s i m p l e w o r s t - c a s e condition is com monly used for design because even significant deviations do not offer much relief. Note that the capacitor manufacturer's ripple current ratings are often based on 2000 hours of life. This makes it advisable to further derate the capacitor, or choose a capacitor rated at a higher temperature than required. Consult the manufac turer if there is any question.
I Q is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses.
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
100% Duty Cycle Operation As the input voltage approaches the output voltage, the converter turns the P-chan nel transistor continuously on. In this mode the output voltage is equal to the input voltage minus the voltage drop across the P - channel transistor: V OUT = V IN - I LOAD (R dson + R L) where R dson = P-channel switch ON resistance, I L O A D = Output current, R L = Inductor DC resistance UVLO and Soft-Start The reference and the circuit remain reset until the VIN crosses its UVLO threshold. The PAM2306 has an internal soft-start circuit that limits the in-rush current during start-up. This prevents possible voltage drops of the input voltage and eliminates the output voltage overshoot. The soft-start acts as a digital circuit to increase the switch current in several steps to the P-channel current limit (1500mA). Short Circuit Protection The switch peak current is limited cycle-by-cycle to a typical value of 1500mA. In the event of an output voltage short circuit, the device operates with a frequency of 400kHz and minimum duty cycle, therefore the average input current is typically 200mA. Thermal Shutdown When the die temperature exceeds 150C, a reset occurs and the reset remains until the temperature decrease to 120C, at which time the circuit can be restarted.
PAM2306
For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dis sipation reduces to:
PD =IO 2RDSONH +IQ VIN
Since R DS(ON), quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input voltage range. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surrounding airflow and temperature difference between junction and ambient. The maximum power dissipation can be calculated by the following formula:
PD = TJ(MAX) -TA JA
Where TJ(max) is the maximum allowable junction temperature 125C.T A is the ambient temperature and JA is the thermal resistance from the junction to the ambient. Based on the standard JEDEC for a two layers thermal test board, the thermal resistance JA of DFN3X3 is 60C/W. The maximum power dissipation at T A = 25C can be calculated by following formula: P D=(125C-25C)/60C/W=1.66W Setting the Output Voltage The internal reference is 0.6V (Typical). The output voltage is calculated as below:
ae R1 o VO=0.6x1+ c R2 / e o
The output voltage is given by Table 1. Table 1: Resistor selection for output voltage setting
Vo 1.2V 1.5V 1.8V 2.5V 3.3V R1 100k 150k 200k 380k 540k R2 100k 100k 100k 120k 120k
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PCB Layout Check List When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the PAM2306. These items are also illustrated graphically in Figure 1. Check the following in your layout: 1. The power traces, consisting of the GND trace, the SW trace and the VIN trace should be kept short, direct and wide. 2. Does the FB pin connect directly to the feedback resistors? The resistive divider R1/R2 must be connected between the (+) plate of C OUT and ground. 3. Does the (+) plate of CIN connect to VIN as closely as possible? This capacitor provides the AC current to the internal power MOSFETs. 4. Keep the switching node, SW, away from the sensitive FB node. 5. Keep the (-) plates of C IN and C OUT as close as possible. Top Bottom
PAM2306
Figure 1 :PAM2306 Suggested Layout
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Ordering Information
PAM 2306 X X X v 1 v 2
Output Voltage 2 Output Voltage 1 Number of Pins Package Type Pin Configuration
Pin Configuration A Type 1. VIN2 2. LX2 3. GND 4. FB1 5. NC1 6. EN1 7. VIN1 8. LX1 9. GND 10. FB2 11: NC2 12 :EN2 Package Type Y: WDFN 3x3 Number of Pins P: 12 Output Voltage v1 K: 3.3V H: 2.8V G: 2.5V E: 1.8V C: 1.5V B: 1.2V A: Adj v2 K: 3.3V H: 2.8V G: 2.5V E: 1.8V C: 1.5V B: 1.2V A: Adj
Part Number PAM2306AYPv1v2
Marking 2306v1v2 XXXYW
Package Type WDFN3x3-12
Standard Package 3,000 Units/Tape&Reel
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Dual High-Efficiency PWM Step-Down DC-DC Coverter
PAM2306
Outline Dimensions
3x3 mm WDFN 12
2
1
2
1
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 A A1 A3 b D D2 E E2 e L
Dimensions In Millimeters Min 0. 700 0. 000 0. 175 0. 150 2. 950 2. 300 2. 950 1. 400 0. 450 0. 350 0. 450 Max 0. 800 0. 050 0. 250 0. 250 3. 050 2. 650 3. 050 1. 750
Dimensions In Inches Min 0. 028 0. 000 0. 007 0. 006 0. 116 0. 091 0. 116 0. 055 0. 018 0. 014 0. 018 Max 0. 031 0. 002 0. 010 0. 010 0. 120 0. 104 0. 120 0. 069
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