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19-1678; Rev 0; 4/00
Network Interface Card Smart Regulator
General Description
The MAX1810 powers peripheral component interconnect (PCI) Ethernet network interface cards (NICs), modem cards, and other devices that utilize both the main and auxiliary (standby) voltages supplied by PCIcompliant systems. The device generates an uninterrupted +3.3V at up to 500mA from either a +5V main or a +5V standby supply. When both +5V inputs fall below +4.1V, an internal switch connects the +3.3V auxiliary input to the output. An auxiliary switch resistance of only 0.18 minimizes output droop from the +3.3V auxiliary supply. In addition, the MAX1810 guarantees that no reverse current flows from the output to any unbiased or inactive input, and remains stable with as little as 1F of output bypass capacitance at its output. The MAX1810 is available in a compact 8-pin highpower (0.9W) SO package. o Uninterrupted +3.3V Output o Up to 500mA Output Current o High-Power 0.9W SO-8 Package o Thermal and Overcurrent Protection o Only 1F Output Capacitor o Internal 0.18 +3.3V Auxiliary Switch o No Reverse Current to Inactive Inputs
Features
MAX1810
________________________Applications
PCI Adapter Cards Network Interface Cards Modem Cards
PART MAX1810ESA
Ordering Information
TEMP. RANGE -40oC to +85oC PIN-PACKAGE 8 SO
Typical Operating Circuit
TOP VIEW
+5V MAIN INPUT MAIN OUT OUT +3.3V, 500mA COUT 1.0F +5V STBY INPUT STBY STBY 1
Pin Configuration
8 7
GND GND GND GND
MAX1810
MAIN 2
MAX1810
OUT 3 6 5 AUX 4
+3.3V AUX INPUT
AUX
GND
SO
________________________________________________________________ Maxim Integrated Products
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Network Interface Card Smart Regulator MAX1810
ABSOLUTE MAXIMUM RATINGS
MAIN, STBY, AUX, OUT to GND ...........................-0.3V to +6.0V OUT to AUX ...........................................................-0.3V to +6.0V OUT Maximum Output Current .......................................1750mA Continuous Power Dissipation (TA = +70C) 8-Pin SO (derate 11.75mW/C above +70C)..............900mW 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
(VMAIN = VSTBY = +5.0V, VAUX = +3.3V, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER MAIN or STBY Input Range AUX Input Range Maximum Load Current MAIN or STBY Quiescent Current AUX Quiescent Current Reverse Leakage from AUX to MAIN or STBY Reverse Leakage from MAIN or STBY to AUX OUT Load Capacitance MAIN or STBY Detect Threshold MAIN or STBY High Threshold MAIN or STBY Hysteresis OUT Voltage OUT Line Regulation OUT Load Regulation AUX to OUT Voltage Drop AUX Switch Resistance AUX Disable Threshold Thermal Shutdown Thermal Shutdown Hysteresis Current-Limit Threshold VAUX = VOUT = 0 520 +4.5V < (VMAIN or VSTBY) < +5.5V, 0 < IOUT < 400mA +4.5V< (VMAIN or VSTBY) < +5.5V IOUT = 30mA to 400mA, VMAIN or VSTBY = +5V IOUT = 400mA MAIN = STBY = GND 2.5 170 20 900 1750 3.234 IOUT = 10mA VMAIN = VSTBY = 0, VAUX = +3.6V VAUX = +3.6V, VMAIN or VSTBY = 0 VAUX = 0, VMAIN or VSTBY = +5.5V COUT ESR < 50m MAIN or STBY falling MAIN or STBY rising 150 3.3 0.01 0.22 72 0.180 118 0.295 2.8 3.366 3.925 CONDITIONS MIN 4.5 3.0 500 0.75 0.2 1 1 1 4.100 4.275 4.475 3 0.5 20 100 TYP MAX 5.5 3.6 UNITS V V mA mA mA A A F V V mV V % % mV V C C mA
2
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Network Interface Card Smart Regulator
ELECTRICAL CHARACTERISTICS
(VMAIN = VSTBY = +5.0V, VAUX = +3.3V, TA = -40C to +85C, unless otherwise noted.) (Note 1)
PARAMETER MAIN or STBY Input Range AUX Input Range Maximum Load Current MAIN or STBY Quiescent Current AUX Quiescent Current Reverse Leakage from AUX to MAIN or STBY Reverse Leakage from MAIN or STBY to AUX MAIN or STBY Detect Threshold MAIN or STBY High Threshold OUT Voltage AUX to OUT Voltage Drop AUX Switch Resistance AUX Disable Threshold Current-Limit Threshold IOUT = 10mA VMAIN = VSTBY = 0, VAUX = +3.6V VAUX = +3.6V, VMAIN or VSTBY = 0 VAUX = 0, VMAIN or VSTBY = +5.5V MAIN or STBY falling MAIN or STBY rising +4.5V < (VMAIN or VSTBY) < +5.5V, 0 < IOUT < 400mA IOUT = 400mA MAIN = STBY = GND VAUX = VOUT = 0 2.5 520 3.234 3.925 CONDITIONS MIN 4.5 3.0 500 3 0.5 20 100 4.275 4.475 3.366 118 0.295 2.8 1750 MAX 5.5 3.6 UNITS V V mA mA mA A A V V V mV V mA
MAX1810
Note 1: Specifications to -40C are guaranteed by design, not production tested.
Typical Operating Characteristics
(VMAIN, VSTBY = +5V, VAUX = +3.3V, COUT = 1F, TA = +25C unless otherwise noted.)
OUTPUT VOLTAGE vs. AUX INPUT VOLTAGE
MAX1810-02 MAX1810-01
MAIN OR STANDBY UNDERVOLTAGE LOCKOUT
3.5 3.0 OUTPUT VOLTAGE (V) 2.5 2.0 1.5 1.0 0.5 0 0 1 2 3 4 5 INPUT VOLTAGE (V) 4.0 3.5 OUTPUT VOLTAGE (V) 3.0 2.5 2.0 1.5 1.0 0.5 0 0 0.5 IOUT = 250mA
OUTPUT VOLTAGE vs. OUTPUT CURRENT (MAIN OR STANDBY)
MAX1810-03
3.35 3.30 OUTPUT VOLTAGE (V) 3.25 3.20 3.15 3.10 3.05 3.00
AUX SWITCH ON AUX SWITCH OFF AUX BODY DIODE ACTIVE
VMAIN AND VSTBY = 0 IOUT = 100mA 1.0 1.5 2.0 2.5 3.0 3.5
0
100
200
300
400
500
600
AUX INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
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Network Interface Card Smart Regulator MAX1810
Typical Operating Characteristics (continued)
(VMAIN, VSTBY = +5V, VAUX = +3.3V, COUT = 1F, TA = +25C unless otherwise noted.)
OUTPUT VOLTAGE vs. OUTPUT CURRENT (AUX)
MAX1810-04
GROUND CURRENT vs. INPUT VOLTAGE (MAIN OR STANDBY)
MAX1810-05
GROUND CURRENT vs. INPUT VOLTAGE (AUX)
MAX1810-06
1000 900 800 GROUND CURRENT (A) 700 600 500 400 300 200 100 0 IOUT = 0 IOUT = 250mA
250
3.9 OUTPUT VOLTAGE (V) 3.7 3.5 3.3 3.1 2.9 2.7 2.5 0 100 200 300 400 500
200 GROUND CURRENT (A) AUX SWITCH ON
150
100
50 VMAIN AND VSTBY = 0 IOUT = 0 0 0 1 2 3 4 5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 INPUT VOLTAGE (V) AUX INPUT VOLTAGE (V)
600
OUTPUT CURRENT (mA)
GROUND CURRENT vs. OUTPUT CURRENT (MAIN OR STANDBY)
MAX1810-07
GROUND CURRENT vs. OUTPUT CURRENT (AUX)
MAX1810-08
AUX ON-RESISTANCE vs. INPUT VOLTAGE
IOUT = 400 mA
MAX1810-09
1400 1200 GROUND CURRENT (A) 1000 800 600 400 200 0 0 100 200 300 400 500 VIN = 4.2V VIN = 5V
250
VMAIN AND VSTBY = 0
240 220 ON-RESISTANCE (m) 200 180 160 140 120
230 GROUND CURRENT (A)
210
190
170
150 600 0 100 200 300 400 500 600 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA)
100 2.6 2.8 3.0 3.2 3.4 3.6 AUX INPUT VOLTAGE (V)
AUX ON-RESISTANCE vs. TEMPERATURE
IOUT = 400mA
MAX1810-10
240 220 ON-RESISTANCE (m) 200 180 160 140 120 100
-40 -25 -10
5
20
35
50
65
80
TEMPERATURE (C)
4
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Network Interface Card Smart Regulator
Typical Operating Characteristics (continued)
(VMAIN, VSTBY = +5V, VAUX = +3.3V, COUT = 1F, TA = +25C unless otherwise noted.)
MAX1810
MAIN OR STANDBY LINE-TRANSIENT RESPONSE
MAX1810-11
MAIN OR STANDBY LOAD-TRANSIENT RESPONSE
MAX1810-12
VIN
5V 4.3V IOUT
200mA 10mA
VOUT
20mV/div AC-COUPLED 10mV/div AC-COUPLED IOUT = 50mA 200s/div 40s/div VOUT
MAIN-T0-STANDBY TRANSITION WAVEFORM
MAX1810-13
MAIN OR STANDBY TO AUX TRANSITION WAVEFORM
MAX1810-14
VMAIN
2V/div
VIN MAIN OR STBY
5V 2.4V
VOUT IOUT = 250mA VSTBY = +5V 20ms/div
50mV/div AC-COUPLED
VOUT IOUT = 250mA VAUX = +3.3V 10ms/div
3.3V 100mV/div DC-COUPLED
Pin Description
PIN 1 2 3 4 5-8 NAME STBY MAIN OUT AUX GND +5V Standby Input +5V Main Input +3.3V Output. Bypass with a 1F capacitor to GND. +3.3V Auxilliary Input Ground. Must connect pins 5 through 8 together to ground plane for power dissipation. FUNCTION
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Network Interface Card Smart Regulator MAX1810
Detailed Description
MAIN 5V DET STBY 5V DET STBY REG MAIN REG 3.3V OUT
AUX 3.3V DET CONTROL LOGIC GND
Figure 1. Functional Diagram
MAIN OR STBY INPUT VOLTAGE 5.5V MAIN OR STBY LDO GUARANTEED ON 4.475V DETECTION THRESHOLD RANGE
The MAX1810 powers NICs, modem cards, or other devices that utilize both the main and auxiliary power supplies in a PCI-compliant system, or other systems that utilize a standby or sleep-mode power bus. The MAX1810 supplies a 3.3V, 500mA output from one of three inputs: a +5V main, a +5V standby, and a +3.3V auxiliary voltage. Each input is separately monitored (Figure 1). During normal operation, the MAIN input powers the fixed +3.3V output (OUT) through an internal linear regulator. When MAIN falls below +4.1V or is disconnected, STBY input powers the output through an internal linear regulator. When the STBY voltage is below +4.1V, an internal switch connects the +3.3V AUX input to OUT. The AUX input maintains the output until AUX falls below +2.5V. Figure 2 shows MAX1810 input transition thresholds. Switchover from one input to another is fast enough to prevent OUT from falling below +3V under all cases unless all inputs are below their required voltages. If both MAIN and STBY are above +4.475V, the MAIN input supplies the output. The MAX1810 prevents reverse current from flowing from the output to any unbiased or low-voltage input.
Linear Regulators
The MAIN or STBY inputs generate the +3.3V output through linear regulators. Each regulator uses an internal P-channel MOSFET pass transistor. The MAIN or STBY linear regulator will operate until its input falls below +4.1V, when it shuts off. Either remaining regulator or AUX input then powers the output. MAIN takes precedence when both MAIN and STBY are valid.
4.1V(TYP)
+3.3V AUX Switch
A 0.18 internal switch connects the AUX input to the output when both MAIN and STBY are below 4.1V and AUX is greater than 2.5V. When both MAIN and STBY are below 4.1V or unconnected, and AUX is below 2.5V, the internal switch does not activate and OUT follows AUX less one diode drop.
3.925V AUX SWITCH GUARANTEED ON (IF AUX > 2.5V) 0
Thermal and Overcurrent Protection
Thermal overload protection limits total power dissipation in the MAX1810. When the junction temperature exceeds T J = +170C, the MAX1810 turns off. The device turns back on once its junction temperature drops by approximately +20C. A continuous short at OUT will result in a pulsed output as the thermal overload circuitry cycles the device on and off.
Figure 2. MAIN, STBY, and AUX Transition Voltages
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Network Interface Card Smart Regulator MAX1810
1.6 MAXIMUM OUTPUT CURRENT (A) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 3.5 4.0 4.5 5.0 5.5 6.0 *REQUIRED ONLY IF INPUT SUPPLIES DO NOT HAVE NEARBY OUTPUT CAPACITANCE. SUPPLY VOLTAGE (V) MAXIMUM CONTINUOUS CURRENT LIMIT TYPICAL SUPPLY VOLTAGE LIMIT UNDERVOLTAGE LOCKOUT LIMIT +5V MAIN INPUT 2.2F +5V STBY INPUT 2.2F +3.3V AUX INPUT 0.1F MAIN * OUT COUT 1.0F STBY * OUT +3.3V, 500mA
TA = +70C TA = +50C
MAX1810
AUX *
GND
TA = +80C TJ(MAX) = +150C
Figure 3. Power Operating Region: Maximum Output Current vs. Supply Voltage
Figure 4. Typical Application Circuit
Thermal overload protection safeguards the MAX1810 in the event of fault conditions. For continuous operation, do not exceed the absolute maximum junctiontemperature rating of TJ = +150C. Both the MAIN and STBY regulators also feature overcurrent protection nominally at 900mA. The AUX switch is not current limited.
Applications Information
Capacitor Selection
The MAX1810 requires a 1F ceramic bypass capacitor at OUT to maintain regulator stability (Figure 4). When switching between input supplies, the MAX1810 may cause a voltage disturbance on either the MAIN or STBY input. Limit this disturbance to below the hysteresis level (150mV) to guarantee precise switchover. If the MAIN and STBY input supplies do not have filter capacitance of their own near the MAX1810 inputs, then bypass capacitors (2.2F is recommended) may be needed at MAIN and STBY. If the input supplies to MAIN and STBY already have greater than 2.2F of output capacitance, then no additional capacitance is required. Place input and output filter capacitors as close to the device as possible to minimize the effect of lead inductance of the PC board traces.
Operating Region and Power Dissipation
Maximum power dissipation of the MAX1810 depends on the thermal resistance of the case and circuit board, the temperature difference between the die junction and ambient air, and the rate of airflow. The power dissipation of the device is P = IOUT (VIN - VOUT). The resulting maximum power dissipation is: PMAX = ((TJ(MAX) - TA) / (JC + CA)) where TJ(MAX) is the maximum junction temperature (150C) and TA is the ambient temperature, JC is the thermal resistance from the die junction to the package case, and CA is the thermal resistance from the case through the PC board, copper traces, and other materials to the surrounding air (Figure 3). For optimum power dissipation, use a large ground plane with good thermal contact to pins 5 through 8. For multilayer boards, multiple vias are recommended.
Chip Information
TRANSISTOR COUNT: 811 PROCESS: BiCMOS
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Network Interface Card Smart Regulator MAX1810
Package Information
SOICN.EPS
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.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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