View MAX1702B_50533.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-2448; Rev 0; 4/02
Triple-Output Power-Management IC for Microprocessor-Based Systems
General Description
The MAX1702B power-management IC supports ARM Powered (R) devices such as the Intel (R) PXA210 and PXA250 microprocessors based on the Intel XScaleTM micro-architecture. These devices include PDAs, thirdgeneration smart cellular phones, internet appliances, automotive in-dash Telematics systems, and other applications requiring substantial computing and multimedia capability at low power. The MAX1702B integrates three ultra-high-performance power supplies with associated supervisory and management functions. Included is a step-down DC-DC converter to supply 3.3V I/O and peripherals, a step-down DC-DC converter to supply 0.7V to VIN for the microprocessor core, and a step-down DC-DC converter to supply either 1.8V, 2.5V, or 3.3V to power the memory. Management functions include automatic power-up sequencing, power-on-reset and manual reset with timer, and two levels of low-battery detection. The DC-DC converters use fast 1MHz PWM switching, allowing the use of small external components. They automatically switch from PWM mode under heavy loads to skip mode under light loads to reduce quiescent current and maximize battery life. The input voltage range is from 2.6V to 5.5V, allowing the use of three NiMH cells, a single Li+ cell, or a regulated 5V input. The MAX1702B is available in a tiny 6mm x 6mm, 36-pin QFN package and operates over the -40C to +85C temperature range.
Features
o Three Regulators in One Package Peripherals and I/O Supply: 3.3V at 900mA P Core Supply: 0.7V to VIN at 400mA Memory Supply: 1.8/2.5/3.3V at 800mA o Supports Intel PXA210 and PXA250 Microprocessors o Power-On Reset with Manual Reset Input o Auto Power-Up Sequencing o 1MHz PWM Switching Allows Small External Components o Low 5A Shutdown Current o Tiny 6mm 6mm, 36-Pin QFN Package
MAX1702B
Ordering Information
PART MAX1702BEGX TEMP RANGE -40C to +85C PIN-PACKAGE 36 6mm x 6mm QFN
Applications
PDA, Palmtop, and Wireless Handhelds Third Generation Smart Cell Phones Internet Appliances and Web Books Automotive In-Dash Telematics Systems
N.C. LBI DBI ON2 PGM3 GND REF 1 2 3 4 5 6 7 8 9 10 IN 11 RSO 12 PG1 13 N.C. INP3
Pin Configuration
OUT3 29
TOP VIEW
N.C. LBO 36 35
COMP3
N.C.
PG3
LX3
34
33
32
31
30
28 27 N.C. 26 N.C. 25 INP2 24 LX2
MAX1702B
FB2 23 PG2 22 OUTOK 21 COMP2 20 OUT1 19 N.C. 18 N.C.
Typical Operating Circuit appears at end of data sheet. Intel is a registered trademark of Intel Corporation. XScale is a trademark of Intel Corporation. ARM and ARM Powered are registered trademarks of ARM Limited.
GND N.C.
14 LX1
15 INP1
16 MR
17 COMP1
6mm x 6mm QFN
________________________________________________________________ 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.
Triple-Output Power-Management IC for Microprocessor-Based Systems MAX1702B
ABSOLUTE MAXIMUM RATINGS
IN, FB2, OUT3, COMP1, COMP2, COMP3, PGM3, ON2, LBO, OUTOK, RSO, MR, LBI, DBI, OUT1 to GND .......................................................-0.3V to +6V REF to GND ...................................................-0.3 to (VIN + 0.3V) INP1, INP2, INP3 to IN...........................................-0.3V to +0.3V PG1, PG2, PG3 to GND.........................................-0.3V to +0.3V LX1, LX2, LX3 Continuous Current .......................-1.5A to +1.5A INP1 to PG1..............................................................-0.3V to +6V INP2 to PG2..............................................................-0.3V to +6V INP3 to PG3..............................................................-0.3V to +6V Output Short-Circuit Duration ............................................Infinite Continuous Power Dissipation (TA =+70C) 36-Pin QFN (derate 22.7 mW/C)..............................1818mW Operating Temperature Range.............................40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+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
(VINP1 = VINP2 = VINP3 = VIN = 3.6V, VLBI = 1.1V, VDBI = 1.35V, MR = ON2 = IN, PGM3 = GND, circuit of Figure 1, TA = -40C to +85C unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER INP1, INP2, INP3, IN Supply Voltage Range Undervoltage Lockout Threshold CONDITIONS INP1, INP2, INP3, IN must be connected together externally VIN rising VIN falling ON2 = IN, no load Quiescent Current (IINP1 + IINP2 + IINP3 + IIN) ON2 = GND, no load VDBI < 1.2 V (shutdown) LX1-3 = GND 3.6V VINP1 5.5V, load = 0 to 900mA 3.234 200 55 Load = 800mA (Note 1) ILX1 = 180mA ILX1 = 180mA, VINP1 = 2.6V ILX1 = 180mA 0.40 1.15 0.115 25 2.6V VINP1 5.5V (Note 2) VINP1 = 5.5V, LX1= GND or INP1, VOUT1 = 3.6V VINP2 = 4.2V 0.9 -20 0 0.1 +20 100 MIN 2.6 2.25 2.2 2.40 2.35 485 335 5 20 A TYP MAX 5.5 2.55 2.525 UNITS V V
SYNCHRONOUS BUCK PWM REGULATOR 1 (REG1) OUT1 Voltage Accuracy OUT1 Input Resistance Error-Amp Transconductance Dropout Voltage P-Channel On-Resistance N-Channel On-Resistance Current-Sense Transresistance P-Channel Current-Limit Threshold P-Channel Pulse-Skipping Current Threshold N-Channel Zero-Crossing Comparator OUT1 Maximum Output Current LX1 Leakage Current LX1 Duty-Cycle Range 3.3 400 95 250 0.25 0.3 0.2 0.47 1.275 0.140 55 135 425 0.4 0.5 0.35 0.54 1.45 0.160 75 3.366 V k S mV V/A A A mA A A %
2
_______________________________________________________________________________________
Triple-Output Power-Management IC for Microprocessor-Based Systems
ELECTRICAL CHARACTERISTICS (continued)
(VINP1 = VINP2 = VINP3 = VIN = 3.6V, VLBI = 1.1V, VDBI = 1.35V, MR = ON2 = IN, PGM3 = GND, circuit of Figure 1, TA = -40C to +85C unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER OUT1 Discharge Resistance CONDITIONS VOUT1 = 3.3V, VDBI = 1V MIN TYP 300 (Note 3) 0.686 150 Load = 400mA (Note 1) ILX2 = 180mA ILX2 = 180mA, VINP2 = 2.6V ILX2 = 180mA 0.40 1.15 0.115 25 2.6V VINP2_ 5.5V (Note 2) VINP2 = 5.5V, LX2 = GND or INP2, VFB2 = 1V VINP_ = 4.2V VLX2 = VDBI = 1V PGM3 = GND, 3.6V VINP3_ 5.5V, load = 0 to 800mA OUT3 Voltage Accuracy PGM3 = REF, 3.6V VINP3_ 5.5V, load = 0 to 800mA PGM3 = IN, 3.6V VINP3_ 5.5V, load = 0 to 800mA PGM3 = GND OUT3 Input Resistance PGM3 = REF PGM3 = IN PGM3 = GND Error-Amp Transconductance Dropout Voltage P-Channel On-Resistance N-Channel On-Resistance PGM3 = REF PGM3 = IN Load = 800mA (Note 1) ILX3 = 180mA ILX3 = 180mA, VINP3 = 2.6V ILX3 = 180mA 0.4 -20 0 300 0.1 +20 100 0.7 1 250 150 0.25 0.3 0.2 0.47 1.275 0.140 55 0.714 150 350 250 0.4 0.5 0.35 0.54 1.45 0.160 75 MAX UNITS
MAX1702B
SYNCHRONOUS BUCK REGULATOR 2 (REG2) FB2 Regulation Voltage FB Input Current Error-Amp Transconductance Dropout Voltage P-Channel On-Resistance N-Channel On-Resistance Current-Sense Transresistance P-Channel Current-Limit Threshold P-Channel Pulse-Skipping Current Threshold N-Channel Zero-Crossing Comparator OUT2 Maximum Output Current LX2 Leakage Current LX2 Duty-Cycle Range LX2 Discharge Resistance 2.6V VINP2 5.5V, load = 0 to 400mA VFB = 0.7V V nA S mV V/A A mA mA A A %
SYNCHRONOUS BUCK REGULATOR 3 (REG3) 1.764 2.45 3.234 340 200 160 105 75 55 1.8 2.5 3.3 650 400 320 175 125 95 220 0.25 0.3 0.2 245 175 135 400 0.4 0.5 0.35 mV S k 1.836 2.55 3.366 V
_______________________________________________________________________________________
3
Triple-Output Power-Management IC for Microprocessor-Based Systems MAX1702B
ELECTRICAL CHARACTERISTICS (continued)
(VINP1 = VINP2 = VINP3 = VIN = 3.6V, VLBI = 1.1V, VDBI = 1.35V, MR = ON2 = IN, PGM3 = GND, circuit of Figure 1, TA = -40C to +85C unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Current-Sense Transresistance P-Channel Current-Limit Threshold P-Channel Pulse-Skipping Current Threshold N-Channel Zero-Crossing Comparator OUT3 Maximum Output Current LX3 Leakage Current LX3 Duty-Cycle Range OUT3 Discharge Resistance REFERENCE REF Output Voltage REF Load Regulation REF Line Regulation OSCILLATOR Switching Frequency THERMAL SHUTDOWN Thermal Shutdown Temperature Thermal Shutdown Hysteresis SUPERVISORY/MANAGEMENT FUNCTIONS Reset Timeout OUTOK Trip Threshold OUTOK, LBO Minimum Assertion Time LBI Input Threshold LBI Input Bias Current VLBI falling VLBI rising VLBI = 0.95V VDBI falling, TA = 0C to +85C VDBI rising, TA = 0C to +85C VDBI falling, TA = -40C to +85C VDBI rising, TA = -40C to +85C DBI Input Bias Current VDBI = 1.25V MR rising to RSO rising VFB2 rising VFB2 falling 55 94 91 107 0.98 1.00 1.2103 1.2345 1.198 1.221 65.5 95.5 92.5 126 1.000 1.020 0.02 1.235 1.2597 1.235 1.260 0.01 75 97.5 94 145 1.02 1.04 0.1 1.2597 1.2849 1.273 1.298 0.1 A V ms % s V A TJ rising 160 15 C C 0.85 1 1.15 MHz 10A < IREF < 100A 2.6V < VBATT < 5.5V 1.225 1.25 2.5 0.6 1.275 6.25 5 V mV mV 2.6V VINP3_ 5.5V (Note 2) VINP3 = 5.5V, LX3 = GND or INP3, VOUT3 = 3.6V VINP3 = 4.2V VOUT3 = 3.3V, VDBI = 1V CONDITIONS MIN 0.40 1.15 0.115 25 0.8 -20 0 300 (Note 3) 0.1 +20 100 TYP 0.47 1.275 0.140 55 MAX 0.54 1.45 0.160 75 UNITS V/A A A mA A A %
DBI Input Threshold
4
_______________________________________________________________________________________
Triple-Output Power-Management IC for Microprocessor-Based Systems
ELECTRICAL CHARACTERISTICS (continued)
(VINP1 = VINP2 = VINP3 = VIN = 3.6V, VLBI = 1.1V, VDBI = 1.35V, MR = ON2 = IN, PGM3 = GND, circuit of Figure 1, TA = -40C to +85C unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER RSO, LBO, OUTOK Output Low Level RSO, LBO, OUTOK Output High Leakage Current ON2, MR, Input High Level ON2, MR, Input Low Level ON2, MR, PGM3, Input Leakage Current PGM3 Selection Threshold CONDITIONS 2.6V VIN_ 5.5V, sinking 1mA VIN_= 1V, sinking 100A V R SO = V L B O = VOUTOK = 5.5V 2.6V VIN_ 5.5V 2.6V VIN_ 5.5V VON2 = V MR = VPGM3 = GND, 5.5V REG3 target = 1.8V, IN = 2.6V to 5.5V REG3 target = 2.5V, IN = 2.6V to 5.5V REG3 target = 3.3V, IN = 2.6V to 5.5V 1.1 VIN_ - 0.25 REF -1 1.6 0.4 +1 0.4 1.4 V MIN TYP MAX 0.4 0.1 UNITS V A V V A
MAX1702B
Note 1: Dropout voltage is not tested. Guaranteed by P-channel switch resistance and assumes a 72m (REG1 and REG3) or 162m (REG2) maximum ESR of inductor. Note 2: The maximum output current is guaranteed by the following equation:
VOUT (1 - D) 2 x xL IOUT(MAX) = (1 - D) 1 + (RN + RL ) 2 x xL ILIM -
where:
D=
VOUT + IOUT(MAX) (RN + RL ) VIN + IOUT(MAX) (RN + RP )
and: RN = N-channel synchronous rectifier RDSON RP = P-channel power switch RDSON RL = external inductor ESR IOUT(MAX) = maximum required load current = operating frequency minimum L = external inductor value Note 3: Specified resistance is in series with an internal diode to LX2. Note 4: Specifications to -40C are guaranteed by design and not production tested.
_______________________________________________________________________________________
5
Triple-Output Power-Management IC for Microprocessor-Based Systems MAX1702B
Typical Operating Characteristics
(Circuit of Figure 1, TA = +25C, unless otherwise noted.)
REG1 EFFICIENCY vs. LOAD CURRENT
MAX1702B toc01
REG3 INCREMENTAL EFFICIENCY vs. LOAD CURRENT
MAX1702B toc02
REG2 INCREMENTAL EFFICIENCY vs. LOAD CURRENT
90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 1000 1 NOTE: INCREMENTAL EFFICIENCY IS REG2 OUTPUT POWER OVER ADDITIONAL INPUT POWER. REG1 AND REG3 QUIESCENT CURRENT IS REFLECTED IN REG1'S EFFICIENCY GRAPH. 10 100 1000 VOUT2 = 1V VOUT2 = 1.3V VOUT2 = 1.1V
MAX1702B toc03
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 1 10 100
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 NOTE: INCREMENTAL EFFICIENCY IS REG3 OUTPUT POWER OVER ADDITIONAL INPUT POWER. REG1 AND REG3 QUIESCENT CURRENT IS REFLECTED IN REG1'S EFFICIENCY GRAPH. 1 10 100 VOUT3 = 1.8V VOUT3 = 3.3V VOUT3 = 2.5V
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
NO LOAD QUIESECNT CURRENT vs. SUPPLY VOLTAGE
MAX1702B toc04
REG1 DROPOUT VOLTAGE vs. LOAD CURRENT (VIN = 3.3V)
MAX1702B toc05
REG3 DROPOUT VOLTAGE vs. LOAD CURRENT (VIN = 3.3V)
140 DROPOUT VOLTAGE (mV) 120 100 80 60 40 20 0 VOUT3 = 3.3V
MAX1702B toc06
0.7 0.6 QUIESCENT CURRENT (mA) 0.5 0.4 0.3 0.2 0.1 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
350 300 DROPOUT VOLTAGE (mV) 250 200 150 100 50 0
160
6.0
0 100 200 300 400 500 600 700 800 900 1000 LOAD CURRENT (mA)
0
50 100 150 200 250 300 350 400 450 LOAD CURRENT (mA)
SUPPLY VOLTAGE (V)
REG1 OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1702B toc07
REG2 OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1702B toc08
REG3 OUTPUT VOLTAGE vs. LOAD CURRENT (VOUT3 = 3.3V)
MAX1702B toc09
3.33 3.31 OUTPUT VOLTAGE (V) 3.29 3.27 TA = -40C 3.25 3.23 3.21 0 100 200 300 400 500 600 TA = 0C TA = +85C
3.325 3.315 OUTPUT VOLTAGE (V) 3.305 3.295 3.285 3.275 3.265 TA = +85C
1.107 1.105 TA = +40C 1.103 1.101 1.099 1.097 1.095 TA = -40C TA = 0C TA = +85C
TA = +40C
OUTPUT VOLTAGE (V)
TA = -40C
TA = 0C
TA = +40C
700
0
50
100
150
200
250
300
0
50 100 150 200 250 300 350 400 450 LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
6
_______________________________________________________________________________________
Triple-Output Power-Management IC for Microprocessor-Based Systems
Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA = +25C, unless otherwise noted.)
REG3 OUTPUT VOLTAGE vs. LOAD CURRENT (VOUT3 = 2.5V)
2.510 OUTPUT VOLTAGE (V) 2.505 2.500 2.495 2.490 2.485 2.480 2.475 0 50 100 150 200 250 300 350 400 450 LOAD CURRENT (mA) TA = -40C TA = 0C 1.787 1.782 0 50 100 150 200 250 300 350 400 450 LOAD CURRENT (mA) TA = +40C TA = +85C
MAX1702B toc10
MAX1702B
REG3 OUTPUT VOLTAGE vs. LOAD CURRENT (VOUT3 = 1.8V)
MAX1702B toc11
2.515
1.812 1.807 TA = +85C OUTPUT VOLTAGE (V) 1.802 1.797 1.792 TA = +40C
TA = -40C
TA = 0C
INTERNAL OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE
MAX1702B toc12
INTERNAL REFERENCE vs. TEMPERATURE
1.29 REFERENCE VOLTAGE (V) 1.28 1.27 1.26 1.25 1.24 1.23 1.22 1.21 1.20
MAX1702B toc13
1040 1020 FREQUENCY (kHz) 1000 980 960 940 920 900 2.5 3.0 3.5 4.0 4.5 5.0 TA = -40C TA = +25C TA = +85C
1.30
5.5
-40
-15
10
35
60
85
SUPPLY VOLTAGE (V)
TEMPERATURE (C)
REG1 HEAVY-LOAD SWITCHING WAVEFORM LOAD = 800mA, VIN = 4V
MAX1702B toc14
REG2 HEAVY-LOAD SWITCHING WAVEFORM LOAD = 400mA, VIN = 4V
MAX1702B toc15
VLX1 2V/div VLX2 2V/div 0 VOUT1 AC-COUPLED 20mV/div IL1 500mA/div CORE 0 400ns/div 0 400ns/div 0 VOUT2 AC-COUPLED 20mV/div IL2 500mA/div
0 I/O
0
_______________________________________________________________________________________
7
Triple-Output Power-Management IC for Microprocessor-Based Systems MAX1702B
Typical Operating Characteristics (continued)
REG3 HEAVY-LOAD SWITCHING WAVEFORM LOAD = 700mA, VIN = 4V
MAX1702B toc16
REG1 MEDIUM-LOAD SWITCHING WAVEFORM LOAD = 100mA, VIN = 4V
MAX1702B toc17
VLX3 2V/div 0 VOUT3 AC-COUPLED 20mV/div IL3 500mA/div 0 400ns/div 0 400ns/div 0
VLX1 2V/div
0
0
VOUT1 AC-COUPLED 20mV/div IL1 500mA/div
REG3 MEDIUM-LOAD SWITCHING WAVEFORM LOAD = 100mA, VIN = 4V
MAX1702B toc18
REG1 LIGHT-LOAD SWITCHING WAVEFORM LOAD = 10mA, VIN = 4V
MAX1702B toc19
VLX3 2V/div 0 VOUT3 AC-COUPLED 20mV/div IL3 500mA/div 0 2s/div 0 10s/div 0
VLX1 2V/div
0
0
VOUT1 AC-COUPLED 20mV/div IL1 500mA/div
REG2 LIGHT-LOAD SWITCHING WAVEFORM LOAD = 10mA, VIN = 4V
MAX1702B toc20
REG3 LIGHT-LOAD SWITCHING WAVEFORM LOAD = 10mA, VIN = 4V
MAX1702B toc21
VLX2 2V/div 0 VOUT2 AC-COUPLED 20mV/div IL2 500mA/div 0 10s/div 0 10s/div 0
VLX3 2V/div
0
0
VOUT3 AC-COUPLED 20mV/div IL3 500mA/div
8
_______________________________________________________________________________________
Triple-Output Power-Management IC for Microprocessor-Based Systems
Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA = +25C, unless otherwise noted.)
TURN-ON SEQUENCE FROM POWER APPLICATION ILOAD1 = 250mA, ILOAD2 = 100mA, ILOAD3 = 200mA
MAX1702B toc22
MAX1702B
TURN-OFF SEQUENCE ILOAD1 = 250mA, ILOAD2 = 100mA, ILOAD3 = 200mA
MAX1702B toc23
VIN 5V/div VOUT1 5V/div VOUT3 5V/div VOUT2 2V/div IIN 500mA/div 0 0 0 0
0 0
0 0
VIN 5V/div VOUT1 5V/div VOUT3 5V/div VOUT2 2V/div IIN 500mA/div VRSO 5V/div 200s/div
0
0 0 20ms/div
VRSO 5V/div 0
TURN-ON DELAY ILOAD1 = 250mA, ILOAD2 = 100mA, ILOAD3 = 200mA
MAX1702B toc24
REG1 LOAD TRANSIENT WAVEFORM LOAD = 100mA TO 500mA, VIN = 4V
MAX1702B toc25
VON2 2V/div 0
VOUT1 AC-COUPLED 200mV/div
0
VOUT2 1V/div IIN 200mA/div
0
ILX1 500mA/div
0 0 40s/div 40s/div
ILOAD1 500mA/div
_______________________________________________________________________________________
9
Triple-Output Power-Management IC for Microprocessor-Based Systems MAX1702B
Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA = +25C, unless otherwise noted.)
REG2 LOAD TRANSIENT WAVEFORM LOAD = 20mA TO 200mA, VIN = 4V
MAX1702B toc26
REG3 LOAD TRANSIENT WAVEFORM LOAD = 75mA TO 400mA, VIN = 4V
MAX1702B toc27
0
VOUT2 AC-COUPLED 100mV/div
0
VOUT3 AC-COUPLED 200mV/div ILX3 200mA/div
0
ILX2 200mA/div 0 ILOAD2 100mA/div 0 40s/div 40s/div ILOAD3 200mA/div
0
LINE TRANSIENT RESPONSE WAVEFORM VIN = 4V TO 5V, ILOAD1 = 250mA, ILOAD2 = 100mA, ILOAD3 = 200mA
MAX1702B toc28
ENTERING AND EXITING DROPOUT WAVEFORM VIN = 2.75V TO 4V, ILOAD1 = 250mA, ILOAD2 = 100mA, ILOAD3 = 200mA
MAX1702B toc29
VIN 2V/div 0 0 0 VOUT1 AC-COUPLED 50mV/div VOUT2 AC-COUPLED 50mV/div VOUT3 AC-COUPLED 20mV/div 400s/div 0
VIN AC-COUPLED 500mV/div VOUT1 AC-COUPLED 500mV/div VOUT3 AC-COUPLED 500mV/div
0 0
0
20ms/div
10
______________________________________________________________________________________
Triple-Output Power-Management IC for Microprocessor-Based Systems
Pin Description
PIN 1, 9, 13, 18, 19, 26, 27, 31, 35 2 NAME N.C. FUNCTION No Connection. These pins are not internally connected. Low-Battery Input. Connect a resistive voltage-divider from the battery voltage to LBI to set the lowbattery threshold. LBI threshold voltage is 1.235V. Dead-Battery Input. Connect a resistive voltage-divider from the battery voltage to DBI to set the dead-battery voltage threshold. When the voltage at DBI is below the 1.25V threshold, the MAX1702B is turned off and draws only 5A from the battery. REG2 On/Off Input. Drive ON2 high to turn on REG2, drive it low to turn it off. When enabled, the MAX1702B soft-starts REG2, when disabled, the output of REG2 is internally discharged to PG2. REG3 Regulation Voltage-Control Input. Connect PGM3 to IN, REF, or GND to set the REG3 output regulation voltage. Connect PGM3 to GND for 1.8V, REF for 2.5V, and IN for 3.3V. Connect Pin 6 to Pin 8 Reference Output. Output of the 1.25V reference. Bypass REF to GND with a 0.1F or greater capacitor. Analog Ground. Connect GND to a local analog ground plane with no high-current paths. GND should be connected to the main ground plane at a single point as close to the IC and the IN bypass capacitor as possible. Connect the ground of the low-noise components, such as resistive voltagedividers and reference bypass capacitor to the analog ground plane. Analog Supply Input. Bypass IN to GND with a 1F or greater low-ESR capacitor. Reset Output. RSO is low (sinks current to GND) during initial startup or while the manual reset input, MR, is asserted. RSO remains low for 65.5ms after all regulators are in regulation or after MR is deasserted. RSO is an open-drain output. RSO remains high when REG2 is turned off. The RSO line maintains a valid low output for IN as low as 1V. REG1 Power Ground. Connect PG1 directly to a power ground plane. Connect PG1, PG2, PG3 and GND together at a single point as close to the IC as possible. REG1 Power-Switching Node. Connect the external inductor of the REG1 output LC filter from LX1 to OUT1 (see the Inductor Selection section). REG1 Power Input. Bypass INP1 to PG1 with a 1.0F or greater low-ESR capacitor. INP1, INP2, INP3, and IN must be connected together externally. A single 4.7F capacitor can be used for INP1, INP2, and INP3. Manual Reset Input. A momentary low on MR forces RSO to go low. RSO remains low as long as MR is low, and returns high 65.5ms after MR returns high and all output voltages are in regulation. REG1 Compensation Node. Connect a series resistor and capacitor from COMP1 to GND in parallel with a 33pF capacitor to compensate REG1 (see the Compensation and Stability section).
MAX1702B
LBI
3
DBI
4 5 6 7
ON2 PGM3 GND REF
8
GND
10
IN
11
RSO
12 14
PG1 LX1
15
INP1
16 17
MR COMP1
______________________________________________________________________________________
11
Triple-Output Power-Management IC for Microprocessor-Based Systems MAX1702B
Pin Description (continued)
PIN 20 21 NAME OUT1 COMP2 FUNCTION REG1 Output-Voltage Sense Input. Bypass OUT1 to PG1 with a 10F or greater low-ESR capacitor (see the Output Capacitor Selection section). REG2 Compensation Node. Connect a series resistor and capacitor from COMP2 to GND in parallel with a 33pF capacitor to compensate REG2 (see the Compensation and Stability section). Output-OK Output. OUTOK sinks current to GND when the voltage at REG2 is below the regulation threshold. When the output is in regulation, OUTOK is high impedance. OUTOK is used by the processor to indicate when it is safe for the processor to exit sleep mode. OUTOK is an open-drain output. OUTOK maintains a valid low output for IN as low as 1V. REG2 Power Ground. Connect PG2 directly to a power ground plane. Connect PG1, PG2, PG3, and GND together at a single point as close to the IC as possible. REG2 Power-Switching Node. Connect the external inductor of the REG2 output LC filter from LX2 to OUT2. LX2 discharges OUT2 when REG2 is disabled (see the Inductor Selection section). REG2 Power Input. Bypass INP2 to PG2 with a 1.0F or greater low-ESR capacitor. INP1, INP2, INP3, and IN must be connected together externally. A single 4.7F capacitor can be used for INP1, INP2, and INP3. REG2 Feedback-Sense Input. Set the REG2 output voltage with a resistive voltage-divider from the REG2 output voltage to FB2. The FB2 regulation threshold is 0.7V. Connect FB2 directly to OUT2 for an output voltage of 0.7V. REG3 Output-Voltage Sense Input. Bypass OUT3 to GND with a 10F or greater low-ESR capacitor (see the Output Capacitor Selection section). REG3 Compensation Node. Connect a series resistor and capacitor from COMP3 to GND in parallel with a 33pF capacitor to compensate REG3 (see the Compensation and Stability section). REG3 Power Ground. Connect PG3 directly to a power ground plane. Connect PG1, PG2, PG3, and GND together at a single point as close to the IC as possible. REG3 Power-Switching Node. Connect the external inductor of the REG3 output LC filter from LX3 to OUT3 (see the Inductor Selection section). REG3 Power Input. Bypass INP3 to PG3 with a 1.0F or greater low-ESR capacitor. INP1, INP2, INP3, and IN must be connected together externally. A single 4.7F capacitor can be used for INP1, INP2, and INP3. Low-Battery Output. LBO sinks current to GND when the voltage at LBI is below the LBI threshold voltage; LBO is high impedance when LBI is above the threshold. LBO is an open-drain output. LBO maintains a valid low output level for IN as low as 1V.
22
OUTOK
23 24
PG2 LX2
25
INP2
28
FB2
29 30 32 33
OUT3 COMP3 PG3 LX3
34
INP3
36
LBO
12
______________________________________________________________________________________
Triple-Output Power-Management IC for Microprocessor-Based Systems
Functional Diagram
IN
MAX1702B
DBI DEADBATTERY DETECTOR DBO
REG1
INP1
LX1 LBI LBO EN LOWBATTERY DETECTOR REF PG1 DC-DC BUCK WITH SKIP 1MHz PWM REG2 OUTOK ON2 ON/OFF CONTROL LOGIC POK EN LX2 OUT1 COMP1 INP2
REF PG2 DC-DC BUCK WITH SKIP 1MHz PWM REG3 RSO MR EN LX3 FB2 COMP2 INP3
output, providing up to 400mA output current. The third output, REG3, is designed to power memory. REG3 output voltage is set to one of 3 voltages; 3.3V (PGM3 = IN), 2.5V (PGM3 = REF), or 1.8V (PGM3 = GND) and delivers up to 800mA of output current. All three regulators utilize a proprietary regulation scheme allowing PWM operation at medium to heavy loads, and automatically switch to pulse skipping at light loads for improved efficiency. Under low-battery conditions, the MAX1702B issues a warning (LBO output). The MAX1702B employs PWM control at medium and heavy loads, and skip mode at light loads (below approximately 80mA) to improve efficiency and reduce quiescent current to 485A. During skip operation, the MAX1702B switches only as needed to service the load, reducing the switching frequency and associated losses in the internal switch, the synchronous rectifier, and the external inductor. There are three steady-state operating conditions for the MAX1702B. The device performs in continuous conduction for heavy loads. The inductor current becomes discontinuous at light loads, requiring the synchronous rectifier to be turned off before the end of a cycle as the inductor current reaches zero. The device enters into skip mode when the converter output voltage exceeds its regulation limit before the inductor current reaches the pulse-skip threshold. During skip mode, a switching cycle initiates when the output voltage drops below the regulation voltage. The P-channel MOSFET switch turns on and conducts current to the output-filter capacitor and load until the inductor current reaches the pulse-skip current threshold. Then the main switch turns off, and the current flows through the synchronous rectifier to the output-filter capacitor and the load. The synchronous rectifier is turned off when the inductor current approaches zero. The MAX1702B waits until the output voltage drops below the regulation voltage again to initiate the next cycle.
MAX1702B
RESET TIMER
REF PG3 DC-DC BUCK WITH SKIP 1MHz PWM OUT3 COMP3 PGM3 GND REF
BANDGAP REFERENCE
100% Duty-Cycle Operation
If the inductor current does not rise sufficiently to supply the load during the on-time, the switch remains on, allowing operation up to 100% duty cycle. This allows the output voltage to maintain regulation while the input voltage approaches the regulation voltage. Dropout voltage is the output current multiplied by the on-resistance of the internal switch and inductor, approximately 220mV for an 800mA load for REG1 and REG3 and 150mV for a 400mA load on REG2. Near dropout, the on-time may exceed one PWM clock cycle; therefore, small amplitude subharmonic ripple can occur in the output voltage. During dropout, the
13
Detailed Description
The MAX1702B triple-output step-down DC-DC converter is ideal for powering PDA, palmtop, and subnotebook computers. Normally, these devices require separate power supplies for the processor core, memory, and the peripheral circuitry. The MAX1702B's REG1 provides a fixed 3.3V output designed to power the microprocessor I/O and other peripheral circuitry. REG1 delivers up to 900mA output current. The microprocessor core is powered from REG2, which has an adjustable 0.7V to VIN
______________________________________________________________________________________
Triple-Output Power-Management IC for Microprocessor-Based Systems MAX1702B
high-side P-channel MOSFET turns on, and the controller enters a low-current consumption mode. The device remains in this mode until the MAX1702B is no longer in dropout.
REG1 and REG3 Step-Down Converters
REG1 and REG3 are 1MHz PWM, current-mode stepdown converters and generate 3.3V at up to 900mA (REG1), and 3.3V, 2.5V, or 1.8V at up to 800mA (REG3). Internal switches and synchronous rectifiers are integrated for small size and improved efficiency. Both regulators remain on while the input voltage is above the UVLO threshold and DBI is above the DBI threshold. REG1 and REG3 cannot be independently turned on or off. To turn both regulators off, pull DBI below the DBI threshold (1.235V typ). The REG3 output voltage is set through the PGM3 pin. Connect PGM3 to IN to set the output voltage to 3.3V, connect it to REF to set it to 2.5V, and connect it to GND to set the voltage to 1.8V.
Synchronous Rectification
An N-channel synchronous rectifier eliminates the need for an external Schottky diode and improves efficiency. The synchronous rectifier turns on during the second half of each cycle (off-time). During this time, the voltage across the inductor is reversed, and the inductor current falls. The synchronous rectifier is turned off at the end of the cycle (at which time another on-time begins) or when the inductor current approaches zero.
Battery Monitoring and Undervoltage Lockout
The MAX1702B does not operate with input voltages below the undervoltage lockout (UVLO) threshold of 2.35V (typ). The inputs remain high impedance until the supply voltage exceeds the UVLO threshold, reducing battery load under this condition. The MAX1702B provides a low-battery comparator that compares the voltage on LBI to the reference voltage. An open-drain output (LBO) goes low when the LBI voltage is below 1V. Use a resistive voltage-divider network as shown in Figure 1 to set the trip voltage to the desired level. LBO is high impedance in shutdown mode. The MAX1702B also provides a dead-battery comparator that turns off the IC when the battery has excessively discharged. When the voltage at DBI is below the 1.235V threshold, the MAX1702B is turned off and draws only 5A from the battery. Use a resistive voltage-divider network as shown in Figure 1 to set the trip voltage to the desired level.
REG2 Step-Down Converter
REG2 is a 1MHz, current-mode step-down converter and generates a 0.7V to VIN output delivering up to 400mA. An internal switch and synchronous rectifier are used for small size and improved efficiency. REG2 is turned on and off through the ON2 input. Drive ON2 low to turn off the regulator, and high to turn it on. OUTOK goes low when the REG2 output voltage drops below 92.5% of the regulation voltage. OUTOK is an open-drain output. OUTOK can be used to signal the processor that the REG2 voltage is in, allowing the processor to exit from sleep mode into run mode.
Reset Output
MAX1702B features an active-low, open-drain reset output (RSO), RSO holds low during startup or when the manual reset input MR is held low. RSO goes high impedance 65.5ms after REG2 reaches its target value and the MR input goes high. (see the Power-On Sequencing section). Note that RSO remains high when REG2 is turned off.
Power-On Sequencing
The MAX1702B starts when the input voltage rises above the UVLO threshold and the voltage at DBI is greater than the DBI threshold. When power is initially applied, REG1 starts in soft-start mode. Once OUT1 reaches its regulation voltage, REG3 ramps to its target in soft-start mode. Finally, once OUT3 reaches its regulation voltage, REG2 ramps to its target in soft-start mode. The RSO output holds low during this time and remains low until 65.5ms after REG2 reaches its target output voltage. Once all the regulators are running, ON2 turns REG2 on and off. During startup (before the end of the reset period) REG2 is enabled and can only be turned off once the RSO output goes high. When turned off, the REG2 output voltage is discharged to PG2 through LX2.
Applications Information
Setting the Output Voltages
The REG1 output voltage is fixed at 3.3V and cannot be changed. The REG3 output voltage can be set by the PGM3 input to either 3.3V (connect PGM3 to IN), 2.5V (connect PGM3 to REF), or 1.8V (connect PGM3 to GND). The REG2 output voltage is set between 0.70V and VIN through a resistive voltage-divider from the REG2 output voltage to FB2 (Figure 1). Select feedback resistor R5 to be less than 14k. R4 is then given by: V R4 = R5 OUT - 1 VFB2 where VFB2 = 0.70V and VOUT is the REG2 output voltage.
14
______________________________________________________________________________________
Triple-Output Power-Management IC for Microprocessor-Based Systems
Compensation and Stability
Compensate each regulator by placing a resistor and a capacitor in series, from COMP_ to GND and connect a 33pF capacitor from COMP_ to GND for improved noise immunity (Figure 1). The capacitor integrates the current from the transconductance amplifier, averaging output-voltage ripple. This sets the device speed for transient responses and allows the use of small ceramic output capacitors. The resistor sets the proportional gain of the output error voltage by a factor gm RC. Increasing this resistor also increases the sensitivity of the control loop to the output-voltage ripple. This resistor and capacitor set a compensation zero that defines the system's transient response. The load pole is a dynamic pole, shifting frequency with changes in load. As the load decreases, the pole frequency shifts lower. System stability requires that the compensation zero must be placed properly to ensure adequate phase margin (at least 30). The following is a design procedure for the compensation network: 1) Select an appropriate converter bandwidth (fC) to stabilize the system while maximizing transient response. This bandwidth should not exceed 1/5 of the switching frequency. Use 100kHz as a reasonable starting point. 2) Calculate the compensation capacitor, COMP_, based on this bandwidth. Calculate COMP1 and COMP3 with the following equation: VOUT(MAX) 1 1 CCOMP1/ 3 = gm IOUT(MAX) RCS 2 x x f where RCS is the regulator's current-sense transresistance and gm is the regulators error amplifier transconductance. Calculate COMP2 with the following equation:
VOUT(MAX) 1 1 R5 CCOMP2 = 2 x x f gm x R4 + R5 IOUT(MAX) RCS
the output capacitor, COUT (see the Output Capacitor Selection section). Calculate the compensation resistance (RC) value to cancel out the dominant pole created by the output load and the output capacitance: 1 1 = 2 x x RL x COUT 2 x x RC x CCOMP_ Solving for RC gives: R x COUT RC = L CCOMP _ To find CCOMPHF_, calculate the high-frequency compensation pole to cancel the zero created by the output capacitor's equivalent series resistance (ESR): 1 1 = 2 x x RESR x COUT 2 x x RC x CCOMPHF_ Solving for CCOMPHF_ gives: R x COUT CCOMPHF _ = ESR , but not less than 33pF RC If low-ESR ceramic capacitors are used, the CCOMPHF_ equation can yield a very small capacitance value. In such cases, do not use less than 33pF to maintain noise immunity.
MAX1702B
Inductor Selection
A 4.7H inductor with a saturation current of at least 1.5A is recommended for most applications. For best efficiency, use an inductor with low ESR. See Table 1 for recommended inductors and manufacturers. For most designs, a reasonable inductor value (LIDEAL) can be derived from the following equation: LIDEAL = VOUT (VIN - VOUT ) VIN x LIR x IOUT(MAX) x fOSC
where RCS is REG2's current-sense transresistance and gm is REG2's error-amplifier transconductance. Calculate the equivalent load impedance, RL, by: RL = VOUT(MIN) IOUT(MAX)
where LIR is the inductor current ripple as a percentage of the load current. LIR should be kept between 20% and 40% of the maximum load current for best performance and stability. The maximum inductor current is: LIR ILMAX = 1 + IOUT(MAX) 2
where VOUT(MIN) equals the minimum output voltage. IOUT(MAX) equals the maximum load current. Choose
______________________________________________________________________________________
15
Triple-Output Power-Management IC for Microprocessor-Based Systems MAX1702B
Table 1. Suggested Inductors
MANUFACTURER Coilcraft Coilcraft Sumida Sumida Sumida PART NUMBER DO1606 LPT1606-472 CDRH4D28-4R7 CDRH5D18-4R1 CR43 INDUCTANCE (H) 4.7 4.7 4.7 4.1 4.7 ESR (mW) 120 240 (max) 56 57 108.7 SATURATION CURRENT (A) 1.2 1.2 1.32 1.95 1.15 DIMENSIONS (mm) 5.3 x 5.3 x 2 6.5 x 5.3 x 2.0 4.6 x 5 x 3 5.5 x 5.5 x 2 4.5 x 4 x 3.5
The inductor current becomes discontinuous if IOUT decreases to LIR/2 from the output current value used to determine LIDEAL.
Setting the Battery Detectors
The low-battery and dead-battery detector trip points can be set by adjusting the resistor values of the divider string (R1, R2, and R3) in Figure 1 according to the following: 1) Choose R3 to be less than 250k 2) R1 = R3 VBL (1 - VTH/VBD) 3) R2 = R3 (VTH VBL/VBD - 1) where VBL is the low-battery voltage, VBD is the deadbattery voltage, and VTH = 1.235V.
Input Capacitor Selection
The input capacitor reduces the current peaks drawn from the battery or input power source and reduces switching noise in the IC. The impedance of the input capacitor at the switching frequency should be less than that of the input source so high-frequency switching currents do not pass through the input source but instead are shunted through the input capacitor. The input capacitor must meet the ripple-current requirement (IRMS) imposed by the switching currents. The input capacitor RMS current is:
IRMS = ILOAD VOUT (VIN -VOUT ) VIN
PC Board Layout and Routing
High switching frequencies and large peak currents make PC board 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 inductor, input filter capacitor, and output filter capacitor as close together as possible, and keep their traces short, direct, and wide. Connect their ground pins to a single common power ground plane. The external voltage-feedback network should be very close to the FB pin, within 0.2in (5mm). Keep noisy traces (from the LX pin, for example) away from the voltage-feedback network; also, keep them separate, using grounded copper. Connect GND and PG_ pins together at a single point, as close as possible to the MAX1702B. Refer to the MAX1702B evaluation kit for a PC board layout example.
Output Capacitor Selection
The output capacitor is required to keep the output-voltage ripple small and to ensure regulation control-loop stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors are recommended. The output ripple is approximately: 1 VRIPPLE LIR x IOUT(MAX) x ESR + 2 x fOSC x COUT See the Compensation and Stability section for a discussion of the influence of output capacitance and ESR on regulation control-loop stability. The capacitor voltage rating must exceed the maximum applied capacitor voltage. Consult the manufacturer's specifications for proper capacitor derating. Avoid Y5V and Z5U dielectric types due to their huge voltage and temperature coefficients of capacitance and ESR. X7R and X5R dielectric types are recommended.
Chip Information
TRANSISTOR COUNT: 10,890 PROCESS: BiCMOS
16
______________________________________________________________________________________
Triple-Output Power-Management IC for Microprocessor-Based Systems
Typical Operating Circuit
INPUT 2.6V TO 5.5V 4.7F 4.7F
MAX1702B
IN INP1 INP2 INP3 R1 162k DBI R2 53.6k LBI R3 86.6k LX1
4.7H
VOUT1 3.3V AT 900mA COUT1 10F
PG1 OUT1 CCOMP1 RCOMP1 1000pF 33k COMP1 CCOMPHF1 33pF
MAX1702B
4.7H LX2 8.06k PG2 FB2 100k COMP2 OUTOK CCOMPHF2 33pF CCOMP2 RCOMP2 14k 680pF 18k COUT2 10F VOUT2 1.1V AT 400mA
LBO OUT1 100k
OUT1 100k
ON2 4.7H LX3 COUT3 10F RSO PG3 OUT3 MR CCOMP3 RCOMP3 1000pF 22k COMP3 CCOMPHF3 33pF VOUT3 3.3V/2.5V/1.8V AT 800mA
PGM3 GND REF
Figure 1. Typical Operating Circuit ______________________________________________________________________________________ 17
Triple-Output Power-Management IC for Microprocessor-Based Systems MAX1702B
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.)
18
______________________________________________________________________________________
36L,40L, QFN.EPS
Triple-Output Power-Management IC for Microprocessor-Based Systems
Package Information (continued)
(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.)
MAX1702B
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 ____________________ 19 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

▲Up To Search▲

Price & Availability of MAX1702B

	To Download MAX1702B Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .