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LX8821
TM (R)
DUAL CHANNEL 2.5A LOW DROPOUT REGULATOR
PRODUCTION
DATA
SHEET
DESCRIPTION
KEY FEATURES Two Independent Regulated Outputs Wide DC Supply Voltage of 3.0V to 10.0V Accurate Output Voltages Low Tolerance Line (0.5%) and Load (0.5%) Regulation Max. Dropout of 0.6V at Rated Current Independent Thermal and Current Limit Protection Loop Stability Independent of Output Capacitor Type SMT Power Package APPLICATIONS/BENEFITS ASIC, Memory, I/O Low Voltage Logic Supplies Active SCSI Terminators Battery Charging Circuits PC Peripherals Instrumentation
The LX8821 is a positive-voltage linear regulator with one fixed and one adjustable output featuring lowdropout and high accuracy. To maximize efficiency, the LX8821 accepts two supply voltage inputs for the VCONTROL and VPOWER sections. This configuration reduces power dissipation by operating the regulator near dropout (VPWR-VOUT = VDO = 0.4V @ 2A) while providing sufficient operating headroom for the control logic. Each channel can supply up to 2.5A independently with a regulator design optimized for system efficiency by consuming minimal ground current and directing quiescent current to the load The internal voltage reference is trimmed at wafer level, enabling precise output voltages, typically 1% of its specified value.
Power sequencing logic ensures proper startup regardless of the level of VCTRL or VPWR. The LX8821 outputs remain off while VPWR < 2.2V. Thermal and Short Circuit Current Protection are integrated on-chip and operate independently for each regulator output. The LX8821 regulator is stable with a wide range of output capacitance and ESR; typically 10F tantalum or ceramic on the outputs is sufficient. Microsemi uses a low profile power package with low thermal resistance and ease of assembly using surface mount technology.
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IMPORTANT: For the most current data, consult Microsemi's website: http://www.microsemi.com
PRODUCT HIGHLIGHT
VPOWER
10F
VPWR Part VCONTROL
1F
VOUT1 VOUT2
R1
33F
VOUT1 VOUT2
R1 VOUT2 = 1.25 * 1 + + I ADJ * R1 R2
VCONTROL
GND LX8821
ADJ
33F R2
GROUND
LX8821 LX8821
PACKAGE ORDER INFO
TA (C) 0 to 100
Output V1 1.5V
Output V2 Adjustable
DF
Plastic S-Pak 7-Pin
RoHS Compliant
LX8821CDF
Note: Available in Tape & Reel. Append the letters "TR" to the part number. (i.e. LX8821CDF-TR)
Copyright (c) 2005 Rev. 1.1, 2005-03-09
Microsemi
Microsemi Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX8821
TM (R)
DUAL CHANNEL 2.5A LOW DROPOUT REGULATOR
PRODUCTION
DATA
SHEET
ABSOLUTE MAXIMUM RATINGS
PACKAGE PIN OUT
TAB is GND
7 6 5 4 3 2 1
Input Voltage (VCTRL, VPWR).........................................................................13.5V Load Current (Internally Limited) ..................................................................3.0A Power Dissipation ......................................................................Internally Limited Short-Circuit Protection .......................................................................... Indefinite Operating Junction Temperature.................................................................. 150C Storage Temperature Range...........................................................-65C to 150C Peak Package Solder Reflow Temperature (40 second maximum exposure) ..................................................... 260C (+0, -5)
Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of specified terminal.
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NC ADJ V2 V OUT2 G ND V PW R V OUT1 V CTRL
DF PACKAGE
(Top View)
Pin 4 and Tab are common RoHS 100% Matte Tin Lead Finish
THERMAL DATA
DF
Plastic S-Pak 7-Pin 4.5C/W 20 - 50C/W
THERMAL RESISTANCE-JUNCTION TO TAB, JT
THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA
Junction Temperature Calculation: TJ = TA + (PD x JA). The JA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow. JA can vary from 10C/W to > 50C/W depending on mounting technique. (See Application Notes Section: Thermal considerations) FUNCTIONAL PIN DESCRIPTION PIN 1 2 3 4 5 6 7 NAME VCTRL VOUT1 VPWR GND VOUT2 ADJ V2 --DESCRIPTION Unregulated input voltage supply, provides bias for control circuitry, (VCTRL - VOUT) > 1V. Regulator #1 fixed output voltage, 1.5V nominal. Unregulated input voltage supply for power section. For proper operation: (VPWR - VOUT) > VDROPOUT. Common terminal for ground reference, Tab of package is internally connected to this pin. Regulator #2 output Regulator #2 feedback voltage, servos to 1.25V. Using external resistors to program VOUT2. Not used, no internal connection, may be left floating or connected to any other pin or voltage.
PACKAGE DATA PACKAGE DATA
Copyright (c) 2005 Rev. 1.1, 2005-03-09
Microsemi
Microsemi Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
LX8821
TM (R)
DUAL CHANNEL 2.5A LOW DROPOUT REGULATOR
PRODUCTION
DATA
SHEET
Unless otherwise specified, the following specifications apply over the operating ambient temperature 0C TA 100C except where otherwise noted and the following test conditions: VCTRL = 5V, VPWR = 3.3V IOUT = 5mA, C1, 2, 3, 4 = 10F (Tantalum), and TJ = TA using low duty cycling methods. Typical values represent performance @ 23C Parameter
FIXED OUTPUT: VOUT 1 Total Output Voltage Variation Line Regulation Load Regulation Current Limit Minimum Load Current ADJUSTABLEOUTPUT: VOUT 2 Output Voltage Line Regulation Load Regulation V2 V2(VIN) V2(I2) VPWR-V2 Dropout Voltage, VOUT 2 VCNTR-V2 Adjust Pin Current Current Limit Minimum Load Current ENTIRE REGULATOR Minimum Operating Voltage Under Voltage Lockout Quiescent Current Ripple Rejection RMS Output Noise Thermal Shutdown TJSD IQ PSRR VPWR VCONTROL VPWR Rising, 3.0VELECTRICAL CHARACTERISTICS
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Symbol
Test Conditions
Min
LX8821 Typ
Max
Units
E ELECTRICALS
C
Note 1: Minimum load current is defined as the amount of output current required to maintain regulation
Copyright (c) 2005 Rev. 1.1, 2005-03-09
Microsemi
Microsemi Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
LX8821
TM (R)
DUAL CHANNEL 2.5A LOW DROPOUT REGULATOR
PRODUCTION
DATA
SHEET
CHARACTERISTIC CURVERS VOUT Error vs. Temperature
0.200% 0.175% 0.150% 0.125% 0.100% 0.075% 0.050% 0.025% 0.000% -0.025% Temp, C 0 25 50 75 100 125 Vo2
VDD (V)
0.70 0.65 0.60 0.55 0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 -50 -25 0
Dropout Voltage
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Error Voltage
Vo1
Iout=2.5A Iout=1A Iout=0.5A
Tem perature (C)
Quiescent Current
8 7
IL1&IL2=5mA IL1&IL2=2.5A
1
Power On Ramp: Supply Ramp
25
50
75
100
125
150
IGROUND (mA)
6 5 4
2
3 2 1 0
3
4
Step Load Response With Ceramic Cap (10F)
CH1 = VO1 , CH2 = V02 , CH4 = IO1 (50mA to 0.55A Step) Copyright (c) 2005 Rev. 1.1, 2005-03-09
-50
-25
Microsemi Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
0
Tem perature (C)
25
50
75
100
125
Microsemi
150
CH1 CH3
2.00V 1.00V
BW CH2
CH4
2.00V 2.00V
BW
M
1.00ms
A
CH1
800mV
CH1 = VP = VC CH2 = VO1
CH3 = VO2 CH4 = IP 2A/DIV
Step Load Response With Tantalum Cap (10F)
GRAPHS GRAPHS
CH1 = VO1 , CH2 = V02 , CH4 = IO1 (50mA to 0.55A Step)
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LX8821
TM (R)
DUAL CHANNEL 2.5A LOW DROPOUT REGULATOR
PRODUCTION
DATA
SHEET
APPLICATION INFORMATION The LX8821 is part of a family of Dual LDO (Low Drop-Out) linear regulators in Microsemi's S-PAK power package which offer maximum power dissipation in a low profile surface mount technology. The family includes combination fixed and adjustable versions. Each channel can supply up to 2.5A independently with a regulator design optimized for system efficiency by consuming minimal ground current and directing quiescent current to the load. INPUT CAPACITOR To improve load transient response and noise rejection an input bypass capacitor is of at least 10F is required. Generally we recommend a 10F ceramic or tantalum or 22F electrolytic capacitor. OUTPUT CAPACITOR The regulator requires output capacitors connected between each output (V1, V2) to GND to stabilize the internal control loop. Many types of capacitors are available, with different capacitance values tolerances, temperature coefficients and equivalent series resistance. We recommend a minimum of 10F. To ensure good transient response from the power supply system under rapidly changing current load conditions, designers generally use additional output capacitors connected in parallel. Such an arrangement serves to minimize the effects of the parasitic resistance (ESR) and inductance (ESL) that are present in all capacitors. The regulator has been tested stable with capacitor ESR's in the range of 0.05 to 2 ohms. We have found it best to use the same type of capacitor for both input and output bypass. ADJUSTABLE OUTPUT VOLTAGE The LX8821 develops a 1.25V reference voltage between the adjust terminal and GND (See Figure 2). By placing a resistor, R2, between these two terminals, a constant current is caused to flow through R1 and down through R2 to set the overall output voltage. Because IADJ is very small and constant when compared with the current through R2, it represents a small error and can usually be ignored. TEMPERATURE PROTECTION The thermal protection shuts the LX8821 down when the junction temperature exceeds 160C. Each output has independent thermal shutdown capability. Exposure to absolute maximum rated conditions for extended periods may affect device reliability: see Thermal Considerations below. CURRENT LIMIT PROTECTION The LX8821 includes over current protection; when the output load current exceeds typically 3A the circuit forces the regulator decrease in output. THERMAL CONSIDERATIONS Thermal shutdown protects the integrated circuit from thermal overload caused from a rise in junction temperature during power dissipation. This means of protection is intended for fault protection only and not as a means of current or power limiting during normal application usage. Proper thermal evaluation should be done to ensure that the junction temperature dose not exceed it's maximum rating. Operating at the maximum TJ of 150C can impact reliability. Due to variation in individual device electrical characteristics and thermal resistance, the built in thermal overload protection may be activated at power levels slightly above or below the rated dissipation. Also peak output power should be considered for each individual output. Power dissipation for regulator can be calculated using the following equation:
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PD = (VIN(MAX) - V1 ) x I1 + (VIN(MAX) - V2 ) x I 2
(Note: power dissipation resulting from quiescent (ground) current is negligible) Thermal resistance, TAB-AMB ranges from 25-450C/W depending on mounting technique using a FR4 copper clad PCB. Junction temperature of the integrated circuit can be calculated using:
VIN
V1
TJUNCTION = TJUNCTION - TAB + TTAB- AMB + TAMB TTAB = PDMAX x JT ; TTAB - AMB = (PDREG1 + PDREG 2 ) x PCB An example: Given conditions: TA = 50C, VIN= 5.0V, V1= 1.5V, I1= 210mA, V2= 3.3V I2= 1A. Calculated values:
TJ-TAB REG1 = (5V - 1.5V) x (0.21A) x 4.5 C/W = (0.735) x 4.5 C/W = 3.3C
Part LX8821
ADJ
IADJ 1A
V2
R1
TJ - TAB REG2 = (5V - 3.3V) x (1A) x 4.5C/W = (1.7) x 4.5C/W = 7.7C
VREF
R2
APPLICATIONS APPLICATIONS
R1 V 2 = VREF 1 + R 2 + I ADJ R1
TTAB- AMB = (0.735W + 1.7W) x 30C/W = 73.1C
TJUNCTION-MAX = 7.7C + 73.1C + 50C = 130.8C
Figure 2 - Basic Adjustable Regulator MINIMUM LOAD REQUIREMENT The LX8821 has a minimum load requirement for proper output regulation. This typical current is specified at 0mA for the fixed output and 1ma for the adjustable output regulators.
It is important to note that although each output of the regulator will produce up to 2.5A in current, the individual or total power dissipation may limit the useful total current draw. The junction temperature should be calculated for each individual output as well as the combined outputs to insure the maximum junction temperature is not exceeded.
Copyright (c) 2005 Rev. 1.1, 2005-03-09
Microsemi
Microsemi Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
LX8821
TM (R)
DUAL CHANNEL 2.5A LOW DROPOUT REGULATOR
PRODUCTION DATA SHEET
MECHANICAL DIMINESIONS
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A
D B K
I
C
H F G
J E
Note: 1. Dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(.006") on any side. Lead dimension shall not include solder coverage MILLIMETERS MIN MAX 9.27 9.52 8.89 9.14 1.77 2.03 7.49 7.74 0.12 0.38 0.58 0.84 1.27 BSC 0.79 1.04 4.31 6.86 0.03 0.13 10.41 10.67 INCHES MIN MAX .365 .375 .350 .360 .070 .080 .295 .305 .005 .015 .023 .033 0.050 BSC .031 .041 .170 .270 .001 .005 .410 .420
Dim A B C D E F G H I J K
MECHANICALS MECHANICALS
PRODUCTION DATA - Information contained in this document is proprietary to Microsemi and is current as of publication date. This document may not be modified in any way without the express written consent of Microsemi. Product processing does not necessarily include testing of all parameters. Microsemi reserves the right to change the configuration and performance of the product and to discontinue product at any time.
Copyright (c) 2005 Rev. 1.1, 2005-03-09
Microsemi
Microsemi Microelectronics Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 6

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