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PAM2301
800mA Step-Down DC-DC Converters
Features
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General Description
The PAM2301 is a step-down current-mode, DCDC 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 1 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 to save power. The PAM2301 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 output voltage is adjustable from 0.6V to the input voltage, while the part number suffix PAM2301XX indicates pre-set output voltage of 3.3V, 2.8V, 2.5V, 1.8V, 1.5V, 1.2V or adjustable. All versions employ internal power switch and synchronous rectifierfor 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. The PAM2301 is available in SOT23-5 package.
Efficiency up to 96% Only 40A(TYP.) Quiescent Current Output Current: Up to 800mA Internal Synchronous Rectifier 1.5MHz Switching Frequency Soft Start Under-Voltage Lockout Short Circuit Protection Thermal Shutdown 5-pin Small SOT23-5 Package Pb-Free Package
Applications
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Cellular Phone Portable Electronics Wireless Devices Cordless Phone Computer Peripherals Battery Powered Widgets Electronic Scales Digital Frame
Typical Application
Fixed Output Voltage
Adjustable Output Voltage
V IN C IN 10F
4
VIN
SW
3 4 . 7H
Vo
Co 10F
V IN C IN 10F
4
VIN
SW
3 4 . 7H
R1 20pF
Vo
Co 10F
1 EN VOUT GND 2
5
1 EN GND 2
FB
5
R2
R1 o ae VO = 0.6 c1 + / e R2 o
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PAM2301
800mA Step-Down DC-DC Converters
Block Diagram
1.5M OSC SLOPE COMP + IAMP VIN
FB FREQ SHIFT R1 R2
VIN OSC
SQ RQ
RS LATCH
+-+
PWM COMP
+
EA
COMP
SWITCHING LOGIC AND BLANKING CIRCUIT
MAIN SWITCH ( PCH )
ANTI SHOOT THRU
SW
SYNCHRONOUS RECTIFIER ( NCH )
EN
0.6VREF
SHUTDOWN
+ IRCMP -
GND
Pin Configuration& Marking Information
Top View SOT23 - 5
VOUT/FB 5
VIN
4
BA V Y W
BA: Product Code of PAM2301 V: Output Voltage Y: Year W: Week
1
EN
2
GND
3
SW
Pin Number 1 2 3 4 5
Name EN GND SW VIN VOUT/FB
Function Enable control input. Force this pin voltage above 1.5V, enables the chip, and below 0.3V shuts down the device. Ground The drains of the internal main and synchronous power MOSFET. Chip main power supply pin VOUT: Output voltage feedback pin, an internal resistive divider divides the output voltage down for comparison to the internal reference voltage. FB: Feedback voltage to internal error amplifier, the threshold voltage is 0.6V.
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PAM2301
800mA Step-Down DC-DC Converters
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 6.6V EN, FB Pin Voltage.............................- 0.3V to V IN SW Pi n Voltage.....................- 0.3V to ( V IN+0.3V ) Junction Temperature................................125 OC Storage Temperature Range........-65 OC to 150 OC Soldering Temperature......................300 OC, 5sec
Recommended Operating Conditions
Supply Voltage................................2.5V to 5.5V Max. Supply Voltage (for Max. duration of 30 minutes)................................................6.0V Ambient Temperature Range..........-40 OC to 85 OC
Thermal Information
Parameter Thermal Resistance (Junction to Case) Thermal Resistance (Junction to Ambient) Internal Power Dissipation Package SOT23-5 SOT23-5 SOT23-5 Symbol JC JA PD Maximum 130 C/W 250 400 mW Unit
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PAM2301
800mA Step-Down DC-DC Converters
Electrical Characteristic
T A=25 OC, V IN=3.6V, V O=1.8V, C IN=10F, C O=10F,L=4.7H, 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 Shutdown Current Oscillator Frequency Drain-Source On-State Resistance SW Leakage Current High Efficiency EN Threshold High EN Threshold Low EN Leakage Current Over Temperature Protection OTP Hysteresis SYMBOL VIN VFB V FB VO IPK LNR LDR IQ ISD fOSC RDS(ON) ILSW VE H VEL IEN OTP OTH 0.01 150 30 1.5 0.3 IO = 100mA VIN=3V,VFB = 0.5V or VO=90% VIN = 2.5V to 5V, IO=10mA IO=1mA to 800mA No load VEN = 0V VO = 100% VFB = 0V or VO = 0V IDS =100mA P MOSFET N MOSFET 1.2 -3 1.2 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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PAM2301
800mA Step-Down DC-DC Converters
Typical Performance Characteristics
T A=25 C, C IN=10 F, C O=10uF,L=4.7 H, unless otherwise noted. Efficiency VS Output Current (Vo=1.2V) Efficiency VS Output Current (Vo=1.5V)
O
100 90 80 70 60 50 40 30 20 10 0 1
100 90
Eifficiency(%)
Efficiency(%)
Vin=2.7V Vin=3.6V Vin=4.2V
80 70 60 50 40 30 20 1 10 100
2.5V 3.6V 4.2V
10
100
1000
1000
Output Current(m A)
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)
Eifficiency VS Output Current (Vo=3.3V)
100 90 80 70 60 50 40 30 20 10 0 1 10 100
Vin=3.6V Vin=4.2V Vin=5.0V
Efficiency(%)
80 70 60 50 40 30 20 1 10 100 Output Current(mA)
3V 3.6V 4.2V
Eifficiency(%)
1000
1000
Output Current(mA)
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PAM2301
800mA Step-Down DC-DC Converters
Typical Performance Characteristics
T A=25 C, C IN=10 F, C O=10uF,L=4.7 H, unless otherwise noted. Efficiency VS Input Voltage ( Vo=1.2V )
100 90
Eifficiency (%)
Efficiency(%)
100 90 80 70 60 50
10mA
O
Efficiency VS Input Voltage ( Vo=1.5V )
80 70 60 50 40 30 20 10 0 2.5
Io=10mA Io=100mA Io=800mA
40 30 2.5
100mA 800mA
3
3.5
4
4.5
5
3.5 4.5 Input Voltage(V)
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
100mA 800mA
40 30
100mA 800mA
3
3.5
4
4.5
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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PAM2301
800mA Step-Down DC-DC Converters
Typical Performance Characteristics
T A=25 C, C IN=10 F, C O=10uF,L=4.7 H, unless otherwise noted. Reference Voltage VS Input Voltage
0.602 0.600 0.598 0.596
Vfb
1.215
O
Output Voltage VS Load Current
1.210
Vin=3.6V
Output Voltage(V)
1.205 1.200 1.195 1.190 1.185 1.180 1.175
0.594 0.592 0.590 0.588 0.586 0.584 2 3 4 Input Voltage 5 6
I=100mA I=600mA I=800mA
Vo=1.2V Vin=3.6V
0 200 400 Load Current(mA) 600 800
0.620
Reference Voltage VS Temperature
Output Voltage VS Temperature
1.194 1.193
Output Voltage(V)
Reference Voltage(V)
0.615 0.610 0.605 0.600 0.595 0.590 0 50 100 150 Tem perature(
1.192 1.191 1.19 1.189 1.188 20 40 60 80 100 120 140 Temperature(
Vo=1.2V Vin=3.6V Io=100mA
Reference Voltage VS Load Current
0.604 0.6 0.596
Vfb
Output Voltage VS Output Current
1.205 1.203 1.201
Output Voltage(V)
Vo=1.2V
1.199 1.197 1.195 1.193
2.5V 3.6V 4.2V 5V
0.592 0.588 0.584 0.58 0 200 400 Load Current 600 800
Vin=2.7V Vin=3.6V Vin=4.2V
1.191 1.189 10 110
210
310
410
510
610
710
810
Output Current(mA)
Power Analog Microelectronics , Inc
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PAM2301
800mA Step-Down DC-DC Converters
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(
R dson VS Input Voltage
0.4
0.6
Rdson VS Temperature
Vin=3.6V
0.5 0.4
Vin=3.6V
0.35
RDS(ON)
0.3
Rds(on)
0.25 0.2 0.15 0.1 2 3 4 Input Voltage 5 6
0.3 0.2 0.1 0 20 70 Temperature() 120
Vin=4.2V Vin=3.6V Vin=2.7V
Oscillator Frequency VS Supply Voltage
1.8
Oscillator Frequency(MHz)
1.58
Oscillator Frequency VS Temperature
Vin=3.6V
Oscillator Frequency(MHz)
1.56
Vin=3.6V
1.7 1.6 1.5 1.4 1.3 1.2 2 3 4 5 Supply Voltage(V) 6 7
1.54
1.52
1.50 20 40 60 80 100 120 140 Temperature(
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PAM2301
800mA Step-Down DC-DC Converters
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=0-800mA Vo=1.8V Vin=3.6V
Voltage Output Voltage Output
O
Load Transient Io=50-800mA Vo=1.8V Vin=3.6V
Inductor Current Output Current
Inductor Current
Output Current
Load Transient Io=200-800mA Vo=1.8V Vin=3.6V
Voltage Output
Start-up from Shutdown Vo=1.8V,Vin=3.6V
Voltage Output
Inductor Current
Enable
Output Current
Inductor Current
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PAM2301
800mA Step-Down DC-DC Converters
Application Information
The basic PAM2301 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 = 320mA (40% of 800mA).
DIL = ae VOUT o VOUT c 1/ f )(L ) VIN o ( e 1
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. Setting the Output Voltage The internal reference is 0.6V (Typical). The output voltage is calculated as below:
(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 1120mA rated inductor should be enough for most applications (800mA + 320mA). For better efficiency, choose a low DC-resis tance inductor. C IN and Cout 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
R1 o ae VO = 0.6 c1 + / e R2 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
This formula has a maximum at VIN =2Vout, where I R M S =Iout/2. This simple worst-case 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. The selection of Cout is driven by the required effective series resistance (ESR).
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PAM2301
800mA Step-Down DC-DC Converters
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 x (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 PAM2301 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. Figure 1 :PAM2301 Suggested Layout PCB Layout Check List When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the PAM2301. 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 V FB pin connect directly to the feedback resistors? The resistive divider R1/R2 must be con nected 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 VFB node. 5. Keep the (-) plates of C IN and C OUT as close as possible.
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PAM2301
800mA Step-Down DC-DC Converters
Ordering Information
PAM 2301 X X X X xxx
Output Voltage Number of Pins Package Type Pin Configuration Output Current
Output Current C: 800mA Pin Configuration A Type 1. EN 2. GND 3. SW 4. VIN 5. VOUT/FB Package Type A: SOT-23 Number of Pins B: 5 Output Voltage 330: 3.3V 280: 2.8V 250: 2.5V 180: 1.8V 150: 1.5V 120: 1.2V ADJ: Adj
Part Number PAM2301CAAB330 PAM2301CAAB280 PAM2301CAAB250 PAM2301CAAB180 PAM2301CAAB150 PAM2301CAAB120 PAM2301CAABADJ
Output Voltage 3.3V 2.8V 2.5V 1.8V 1.5V 1.2V ADJ
Marking BAKYW BAHYW BAGYW BAEYW BACYW BABYW BAAYW
Package Type SOT23-5 SOT23-5 SOT23-5 SOT23-5 SOT23-5 SOT23-5 SOT-23-5
Standard Package 3,000Units/Tape&Reel 3,000Units/Tape&Reel 3,000Units/Tape&Reel 3,000Units/Tape&Reel 3,000Units/Tape&Reel 3,000Units/Tape&Reel 3,000Units/Tape&Reel
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PAM2301
800mA Step-Down DC-DC Converters
Outline Dimensions
c (REF.) 0.25
L REF. L1 (REF.)
SOT23-5
D e1
E1
E
REF. A A1 A2 c D E E1 L L1 b e e1
Min 0 0.70 2.70 2.60 1.40
0 0.30
Millimeter Nom 1.10MAX 0.05 1.00 0.12REF. 2.90 2.80 1.60 0.45REF. 0.60REF. 5 0.40 0.95REF. 1.90REF.
A1
A2
A
Max 0.10 1.295 3.10 3.00 1.80
10 0.50
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