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19-0593; Rev 0; 11/06
2.5MHz/1.5MHz Step-Down Converters with 60m Bypass in TDFN for CDMA PA Power
General Description
The MAX8581/MAX8582 high-frequency step-down converters are optimized for dynamically powering the power amplifier (PA) in CDMA handsets. They integrate a highefficiency PWM step-down converter for medium- and low-power transmission and a 60m (typ) bypass mode to power the PA directly from the battery during highpower transmission. They use an analog input driven by an external DAC to control the output voltage linearly for continuous PA power adjustment. The MAX8581/ MAX8582 use an internal feedback network, and the switching frequency is internally set to 2.5MHz and 1.5MHz, respectively. Fast switching (up to 2.5MHz) and fast soft-start allow the use of ceramic 2.2F input and output capacitors while maintaining low voltage ripple. The small 1.5H to 3.3H inductor size can be optimized for efficiency. The MAX8581/MAX8582 are available in 10-pin, 3mm x 3mm TDFN packages (0.8mm max height). 600mA Step-Down Converter 60m (typ) Bypass Mode with Integrated FET Dynamically Adjustable Output from 0.4V to VIN 2.5MHz and 1.5MHz Switching Frequency Small LC Components: 1.5H to 3.3H and 2.2F Up to 94% Efficiency Low Output Ripple at All Loads 2.7V to 5.5V Input 0.1A Shutdown Mode Output Short-Circuit Protection Thermal Shutdown 10-Pin, 3mm x 3mm TDFN Packag
KIT ATION EVALU BLE AVAILA
Features
MAX8581/MAX8582
Applications
WCDMA/NCDMA Cell Phones Wireless PDAs, Smartphones
PART* MAX8581ETB+ MAX8582ETB+
Ordering Information
PINPACKAGE 10 TDFN-EP** 10 TDFN-EP** TOP MARK ACT ACU PKG CODE T1033-1 T1033-1
*All devices are specified in the -40C to +85C extended temperature range. **EP = Exposed pad. +Denotes lead-free package.
Typical Operating Circuit
INPUT Li+ BATTERY OUTPUT 0.4V TO VBATT IN OUT 1.5H OR 3.3H 2.2F GND
Pin Configuration
TOP VIEW
OUT OUT LX REFIN IC
10
9
8
7
MAX8581 MAX8582
LX 2.2F MAX8581/ MAX8582
6
ON/OFF ANALOG CONTROL
SHDN REFIN HP FORCED BYPASS + 1 GND 2 IN 3 IN 4 SHDN 5 HP
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
2.5MHz/1.5MHz Step-Down Converters with 60m Bypass in TDFN for CDMA PA Power MAX8581/MAX8582
ABSOLUTE MAXIMUM RATINGS
IN, SHDN, HP, REFIN to GND ...............................-0.3V to +6.0V LX, OUT, IC to GND.....................................-0.3V to (VIN + 0.3V) OUT Short Circuit to GND ..........................................Continuous LX Current ......................................................................0.7ARMS IN, OUT Current..............................................................2.5ARMS Continuous Power Dissipation (TA = +70C) 10-Pin TDFN (derate 24.4mW/C above +70C).........1951mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VIN = V SHDN = 3.6V, VREFIN = 0.9V, VHP = VIC = 0V, TA = -40C to +85C, typical values are at TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER SUPPLY Supply Voltage Range UVLO Threshold Supply Current OUT VIN = 4.2V, VREFIN = 1.7V OUT Voltage Accuracy VOUT VIN = 3.6V VLX = VOUT VREFIN = 0.9V VREFIN = 0.4V MAX8581 MAX8582 0 2.00 518 VREFIN rising, 77mV hysteresis 0.45 x VIN 1.4 0.4 TA = +25C TA = +85C 0.01 0.1 1 0.463 x 0.475 x VIN VIN 3.33 1.75 0.75 3.40 1.80 0.80 360 558 2.2 3.47 1.85 0.85 k V VIN UVLO IIN VIN rising, 180mV hysteresis ILOAD = 0A, switching at 1.5MHz Shutdown, TA = +25C Shutdown, TA = +85C 2.7 2.55 2.63 4000 0.1 1.0 10 A 5.5 2.70 V V SYMBOL CONDITIONS MIN TYP MAX UNITS
OUT Input Resistance REFIN REFIN Common-Mode Range REFIN to OUT Gain REFIN Input Resistance REFIN Dual ModeTM Threshold LOGIC INPUTS Logic Input Level Logic Input Bias Current
ROUT
V V/V k V
VIH VIL IIH, IIL
VIN = 2.7V to 5.5V VIN = 2.7V to 5.5V VINPUT = 0V or VIN
V A
Dual Mode is a trademark of Maxim Integrated Products, Inc.
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2.5MHz/1.5MHz Step-Down Converters with 60m Bypass in TDFN for CDMA PA Power
ELECTRICAL CHARACTERISTICS (MAX8582 ONLY) (continued)
(VIN = VSHDN = 3.6V, VREFIN = 0.9, VHP = VIC = 0V, TA = -40C to +85C, typical values are at TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER LX On-Resistance LX Leakage Current p-Channel MOSFET Peak Current Limit n-Channel MOSFET Valley Current Limit Minimum On- and Off-Times tON/tOFF Ratio BYPASS On-Resistance Bypass Current Limit Step-Down Current Limit in Bypass GENERAL Thermal Shutdown Thermal-Shutdown Hysteresis Power-Up Delay VSHDN rising to VLX rising +160 20 50 130 C C s RONBYP p-channel MOSFET bypass, IOUT = -400mA, TA = +25C p-channel MOSFET bypass, IOUT = -400mA 1.0 700 2.1 1077 1400 0.06 0.1 0.12 A mA RONP RONN ILXLKG ILIMP ILIMN tON(MIN) tOFF(MIN) tON(MIN) / tOFF(MIN) p-channel MOSFET switch, ILX = -40mA n-channel MOSFET rectifier, ILX = 40mA VIN = 5.5V, LX = GND TA = +25C TA = +85C 700 790 70 70 0.90 0.2 0.18 0.1 1 1077 985 114 112 1.02 1400 1150 150 150 1.13 0.4 0.35 5 A mA mA ns s/s SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX8581/MAX8582
Note 1: All devices are 100% production tested at TA = +25C. Limits over the operating temperature range are guaranteed by design.
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2.5MHz/1.5MHz Step-Down Converters with 60m Bypass in TDFN for CDMA PA Power MAX8581/MAX8582
Typical Operating Characteristics
(VIN = 3.6V, VOUT = 1.2V, MAX8582 EV Kit, TA = +25C, unless otherwise noted.)
BYPASS MODE DROPOUT VOLTAGE vs. LOAD CURRENT
MAX8581/2 toc01
EFFICIENCY vs. OUTPUT VOLTAGE
MAX8581/2 toc02
EFFICIENCY vs. LOAD CURRENT (VOUT = 1.8V)
90 80 EFFICIENCY (%) 70 60 50 40 30 20
MAX8581/2 toc03
0.08 DROPOUT VOLTAGE (VIN - VOUT) (V) 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 0 0.2 0.4 0.6 0.8 VOUT = 3.6V VOUT = 3.2V
100 95 90 EFFICIENCY (%) 85 80 75 70 65 RLOAD = 7.5 60 0.8 1.2 1.6 2.0 2.4 2.8
100
10 0 3.2 10 100 LOAD CURRENT (mA) 1000
1.0
LOAD CURRENT (A)
OUTPUT VOLTAGE (V)
EFFICIENCY vs. LOAD CURRENT (VOUT = 1.2V)
MAX8581/2 toc04
EFFICIENCY vs. LOAD CURRENT (VOUT = 0.6V)
MAX8581/2 toc05
NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE
8 SUPPLY CURRENT (mA) 7 6 5 4 3 2 1 0
MAX8581/2 toc06
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 10 100 LOAD CURRENT (mA)
90 80 70 EFFICIENCY (%) 60 50 40 30 20 10 0
9
1000
10
100 LOAD CURRENT (mA)
1000
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX8581/2 toc07
OUTPUT VOLTAGE vs. REFIN VOLTAGE
4.0 OUTPUT VOLTAGE VOUT (V) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 RLOAD = 7.5 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 VIN = 4.2V VIN = 3.6V VIN = 3.0V
MAX8581/2 toc08
1.210 1.200 OUTPUT VOLTAGE (V) 1.190 1.180 1.170 1.160 1.150 0 100 200 300 400 500
4.5
0 600 LOAD CURRENT (mA)
REFIN VOLTAGE (V)
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2.5MHz/1.5MHz Step-Down Converters with 60m Bypass in TDFN for CDMA PA Power
Typical Operating Characteristics (continued)
(VIN = 3.6V, VOUT = 1.2V, MAX8582 EV Kit, TA = +25C, unless otherwise noted.)
LIGHT-LOAD SWITCHING WAVEFORMS
MAX8581/2 toc09
MAX8581/MAX8582
HEAVY-LOAD SWITCHING WAVEFORMS
MAX8581/2 toc10
ILOAD = 50mA 600mA ILX 100mA/div 0A ILX ILOAD = 500mA VOUT 20mV/div AC-COUPLED VOUT 20mV/div AC-COUPLED 400mA 200mA
2V/div VLX 200ns/div 0V
VLX 200ns/div
2V/div 0V
SOFT-START WAVEFORMS
MAX8581/2 toc11
LINE-TRANSIENT WAVEFORMS
MAX8581/2 toc12
LOAD TRANSIENT
MAX8581/2 toc13
RLOAD = 7.5 VSHDN VOUT 2V 2V/div 1V/div 0V VOUT 100mA/div 0A ILX 500mA/div 0A VIN 4V 3V VOUT 50mV/div AC-COUPLED
IIN
50mV/div AC-COUPLED IOUT
ILX 20s/div
200mA/div 0A 20s/div
100mA/div 0A
20s/div
REFIN TRANSIENT RESPONSE
MAX8581/2 toc14
REFIN TRANSIENT WITH AUTOBYPASS
MAX8581/2 toc15
HP TRANSIENT RESPONSE WITH FORCED AUTOBYPASS
MAX8581/2 toc16
RLOAD = 7.5 2V VOUT 1V VREFIN 1V 0.5V
VOUT
RLOAD = 7.5 VOUT 2V/div 0V
RLOAD = 7.5 VREFIN = 0.6V 2V/div 0V
VREFIN
1V/div 0V
VHP
1V/div 0V
ILX
500mA/div 0A 500mA/div 0A 20s/div
ILX
500mA/div 0A 500mA/div 0A 20s/div
ILX
200mA/div 0A 20s/div IOUT IOUT
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2.5MHz/1.5MHz Step-Down Converters with 60m Bypass in TDFN for CDMA PA Power MAX8581/MAX8582
Pin Description
PIN 1 2, 3 4 5 6 7 8, 9 10 -- NAME GND IN SHDN HP REFIN IC OUT LX EP Ground Supply Voltage Input. 2.7V to 5.5V. Bypass with a 2.2F ceramic capacitor as close as possible to IN and GND. Active-Low Shutdown Input. Connect to IN or logic-high for normal operation. Connect to GND or logic-low for shutdown mode. High-Power Mode Set Input. Drive HP high to invoke bypass mode. Bypass mode connects IN directly to OUT with the internal bypass MOSFET. DAC-Controlled Input. Output regulates to 2 x VREFIN for the MAX8581 and MAX8582. Dual-mode threshold at 0.465 VIN enables bypass mode. Internally Connected. Connect to ground. Output Voltage Connection for Bypass Mode. Internally connected to IN using the internal bypass MOSFET during bypass mode. Connects to the internal feedback network. Inductor Connection. Connect inductor to the drains of the internal p-channel and n-channel MOSFETs. Connects to the internal feedback network. Exposed Paddle. Connect to GND. FUNCTION
Detailed Description
The MAX8581/MAX8582 step-down converters deliver over 600mA to dynamically power the PA in CDMA handsets. The hysteretic PWM control scheme switches with nearly fixed frequency at 1.5MHz (MAX8582) to 2.5MHz (MAX8581), allowing efficiency and tiny external components. A 60m bypass mode connects the PA directly to the battery during high-power transmission.
Voltage-Positioning Load Regulation
The MAX8581/MAX8582 utilize a unique feedback network. By taking feedback from the LX node, the usual phase lag due to the output capacitor is removed, making the loop exceedingly stable and allowing the use of very small ceramic output capacitors. This configuration yields load regulation equal to half the inductor's series resistance multiplied by the load current. This voltage-positioning load regulation greatly reduces overshoot during load transients or when changing VOUT from one voltage to another. However, when calculating REFIN voltage, the load regulation should be considered. Because inductor resistance is typically well specified and the typical PA is a resistive load, the VREFIN to VOUT gain is slightly less than 2V/V for the MAX8581/MAX8582.
Control Scheme
A hysteretic PWM control scheme ensures high efficiency, fast switching, fast transient response, low output ripple, and physically tiny external components. This control scheme is simple: When the output voltage is below the regulation voltage, the error comparator begins a switching cycle by turning on the high-side switch. This switch remains on until the minimum ontime expires and the output voltage is in regulation or the current-limit threshold is exceeded. Once off, the high-side switch remains off until the minimum off-time expires and the output voltage falls out of regulation. During this period, the low-side synchronous rectifier turns on and remains on until the high-side switch turns on again. The internal synchronous rectifier eliminates the need for an external Schottky diode.
Bypass Mode
During high-power transmission, the bypass mode's low on-resistance provides low dropout, long battery life, and high output-current capability. Bypass mode connects IN directly to OUT with the internal 60m (typ) bypass FET, while the step-down converter is forced into 100% duty-cycle operation to slightly lower total on-resistance to less than 60m (typ).
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2.5MHz/1.5MHz Step-Down Converters with 60m Bypass in TDFN for CDMA PA Power
Applications Information
VIN = 3.2V TO 3.66V 200mV/div
MAX8581/MAX8582
The MAX8581/MAX8582 are optimized for use with a tiny inductor and small ceramic capacitors. The correct selection of external components ensures high efficiency, low output ripple, and fast transient response.
Setting the Output Voltage
The MAX8581/MAX8582 output voltages are set by the voltage applied to REFIN. The output voltage is 2 VREFIN minus half the IR voltage drop caused by the inductor's DC resistance for the MAX8581/MAX8582.
VOUT = 3V 200mV/div 5ms/div
Inductor Selection
The MAX8581/MAX8582 use 1.5H and 3.3H, respectively. Low inductance values are physically smaller but require faster switching, which results in some efficiency loss (see the Typical Operating Characteristics for efficiency). The inductor's DC current rating only needs to match the maximum load of the application because the MAX8581/MAX8582 feature zero current overshoot during startup and load transients. For optimum transient response and high efficiency, choose an inductor with DC series resistance in the 50m to 150m range.
Figure 1. VIN and VOUT with Automatic Entry/Exit into Bypass Mode
Forced and Automatic Bypass Mode Invoke forced-bypass mode by driving HP high or invoke automatic bypass by applying a high voltage to REFIN (VREFIN > 2.1V with a Li-ion (Li+) battery at IN). To prevent excessive output ripple as the step-down converter approaches dropout, the MAX8581/MAX8582 preemptively enter bypass mode automatically when VREFIN > 0.465 VIN (see Figure 1).
Output Capacitor Selection
The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R dielectric are highly recommended due to their small size, low ESR, and small temperature coefficients. Due to the unique feedback network, the output capacitance can be very low. In most applications, 2.2F works well. For optimum load-transient performance and very low output ripple, the output capacitor value can be increased.
Shutdown Mode
Connect SHDN to GND or logic-low to place the MAX8581/MAX8582 in shutdown mode and reduce supply current to 0.1A. In shutdown, the control circuitry, internal switching MOSFET, and synchronous rectifier turn off and LX becomes high impedance. Connect SHDN to IN or logic-high for normal operation.
Fast Soft-Start
The MAX8581/MAX8582 have internal fast soft-start circuitry that limits inrush current at startup, reducing transients on the input source. Soft-start is particularly useful for supplies with high output impedance such as Li+ and alkaline cells. See the Soft-Start Waveforms in the Typical Operating Characteristics.
Input Capacitor Selection
The input capacitor reduces the current peaks drawn from the battery or input power source and reduces switching noise in the MAX8581/MAX8582. The impedance of the input capacitor at the switching frequency should be kept very low. Ceramic capacitors with X5R or X7R dielectric are highly recommended due to their small size, low ESR, and small temperature coefficients. Due to the MAX8581/MAX8582s' fast soft-start, the input capacitance can be very low. In most applications, 2.2F works well. For optimum noise immunity and low input ripple, the input capacitor value can be increased.
Analog REFIN Control
The MAX8581/MAX8582 use REFIN to set the output voltage and to switch to bypass mode. The output voltage is two times the voltage applied at REFIN minus half the IR voltage drop caused by the inductor's DC resistance for the MAX8581/MAX8582. This allows the converter to operate in applications where dynamic voltage control is required.
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2.5MHz/1.5MHz Step-Down Converters with 60m Bypass in TDFN for CDMA PA Power MAX8581/MAX8582
Table 1. Suggested Inductors
MANUFACTURER Coilcraft SERIES LP03310 SD3110 Cooper SD3112 MIPF2520D ELC3FN CDRH2D09 CDRH2D11 CB2016 CBC2016 Taiyo Yuden CB2518 CBC2518 NR3010 MDT2520-CR TOKO D2812C INDUCTANCE (H) 1.5 3.3 1.5 1.5 3.3 1.5 3.3 2.2 1.5 3.3 2.2 2.2 2.2 2.2 1.5 3.3 2.2 1.5 1.3 ESR () 0.10 0.16 0.11 0.10 0.17 0.07 0.10 0.12 0.05 0.10 0.13 0.20 0.09 0.13 0.08 0.14 0.08 0.11 0.17 CURRENT RATING (mA) 1400 950 970 1090 840 1500 1200 1000 680 450 510 750 510 890 1200 840 700 900 730 DIMENSIONS 3.3 x 3.3 x 1.0 = 11mm3 3.1 x 3.1 x 1.05 = 10mm3 3.1 x 3.1 x 1.2 = 12mm3 2.5 x 2.0 x 1.0 = 5mm3 3.2 x 3.2 x 1.2 = 12mm3 3.2 x 3.2 x 1.2 = 12mm3 2.0 x 1.25 x 1.45 = 3.6mm3 2.0 x 1.6 x 1.8 = 5.8mm3 2.5 x 1.8 x 2.0 = 9mm3 3.2 x 3.2 x 1.2 = 12mm3 2.5 x 2.0 x 1.0 = 5mm3 2.8 x 2.8 x 1.2 = 9.4mm3
FDK Panasonic Sumida
PCB Layout
Checklist High switching frequencies and relatively large peak currents make the PCB layout a very important part of design. Good design minimizes excessive EMI on the feedback paths and voltage gradients in the ground plane, both of which can result in instability or regulation errors. Connect the input capacitor close to IN and GND. Connect the inductor and output capacitor as close to the IC as possible and keep their traces short, direct, and wide. Keep noisy traces, such as the LX node, as short as possible. Connect GND to the exposed paddle directly under the IC. Figure 2 illustrates an example PCB layout and routing scheme.
L1 = FDK MIPF2520 SERIES 1.5H FOR MAX8581
3.3H FOR MAX8582 C1, C2 = TAIYO YUDEN JMK105BJ225MV-B L1
GND IN SHDN HP REFIN C1 C2 OUT GND
Chip Information
PROCESS: BiCMOS
Figure 2. Example PCB Layout and Routing Scheme
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2.5MHz/1.5MHz Step-Down Converters with 60m Bypass in TDFN for CDMA PA Power
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
6, 8, &10L, DFN THIN.EPS
MAX8581/MAX8582
PACKAGE OUTLINE, 6,8,10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm
21-0137
H
1 2
COMMON DIMENSIONS SYMBOL A D E A1 L k A2 MIN. 0.70 2.90 2.90 0.00 0.20 MAX. 0.80 3.10 3.10 0.05 0.40
PACKAGE VARIATIONS PKG. CODE T633-1 T633-2 T833-1 T833-2 T833-3 T1033-1 T1033-2 T1433-1 T1433-2 N 6 6 8 8 8 10 10 14 14 D2 1.500.10 1.500.10 1.500.10 1.500.10 1.500.10 1.500.10 1.500.10 1.700.10 1.700.10 E2 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 e 0.95 BSC 0.95 BSC 0.65 BSC 0.65 BSC 0.65 BSC 0.50 BSC 0.50 BSC 0.40 BSC 0.40 BSC JEDEC SPEC MO229 / WEEA MO229 / WEEA MO229 / WEEC MO229 / WEEC MO229 / WEEC MO229 / WEED-3 MO229 / WEED-3 ------b 0.400.05 0.400.05 0.300.05 0.300.05 0.300.05 0.250.05 0.250.05 0.200.05 0.200.05 [(N/2)-1] x e 1.90 REF 1.90 REF 1.95 REF 1.95 REF 1.95 REF 2.00 REF 2.00 REF 2.40 REF 2.40 REF
0.25 MIN. 0.20 REF.
PACKAGE OUTLINE, 6,8,10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm
-DRAWING NOT TO SCALE-
21-0137
H
2 2
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9 (c) 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

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