LTC1041

LTC1041 LINER

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TECHNOLOGY BANG-BANG Controller FEATURES DESCRIPTION = Micropower 1.5uW (1 Sample/Second) The LTC 1041 is a monolithic CMOS BANG-BANG controller #8 Wide Supply Range 2.8V to 16V Manufactured using Linear Technology's enhanced ® High Accuracy LTCMOS™ silicon gate process. BANG-BANG loops are Guaranteed SET POINT Error +0.5mV Max. characterized by turning the control element fully ON or Guaranteed Deadband + 0.1% of Value Max. fully OFF to regulate the average value of the parameter to © Wide Input Voltage Range V* to Ground be controlled. The SET POINT input determines the aver- ®= TTL Outputs with 5V Supply age control value and the DELTA input sets the deadband. 8 Two /ndependent Ground-Referred Control Inputs The deadband is always 2 x DELTA and is centered around = Small Size 8-Pin MiniDIP the SET POINT. Independent control of the SET POINT and deadband, with no interaction, is made possible by the unique sampling input structure of the LTC1041. An external RC connected to the OSC pin sets the sam- APPLICATIONS pling rate. At the start of each sample, internal power to = Temperature Control (Thermostats) the analog section is switched on for ~ 80ys. During this = Motor Speed Control time the analog inputs are sampled and compared. After = Battery Charger the comparison is complete, power is switched off. This = Any ON-OFF Control Loop achieves extremely low average power consumption at low sampling rates. CMOS logic holds the output con- tinuously while consuming virtually no power. To keep system power at an absolute minimum, a switched power output (Vep) is provided. External loads, such as 6 | bridge networks and resistive dividers, can be driven by this switched output. The output logic sense (i.e., ON=V* ) can be reversed (i.e., ON=GND) by interchanging the Vin and SET POINT inputs. This has no other effect on the operation of the LTC1041. LE Ultra Low Power 50°F to 100°F (2.4:W) Thermostat Supply Current vs Sampling Frequency 26VAC 2 WIRE THERMOSTAT 10000 5k Oe ae i son 2 TOTAL SUPPLY YAY ja ris of wom], CURRENT 1B 1k. a & _ 49.991 tak [7 a “ZV TTT 0.1 1 10 100 1000 += 10000 ft RESISTORS 1%. SAMPLING FREQUENCY, fs (Hz) ‘YELLOW SPRINGS INSTRUMENT CO., INC. P/N 44007 DRIVING THERMISTOR WITH Vpp ELIMINATES 3.8°F ERROR OUE 10 SELF-HEATING. ttemos™ is a trademark of Linear Technology Corporation. SE DO We 6-69

— ‘TURE | ORDER PART Operating Temperature Range we Ey, vi a 4 ° HeAMETIC DP ALASTICOIP Test Conditions: V+ =5V, Twin <Ta< Tmax unless otherwise specified. LTC1041M/LTC1041C SET POINT Error (Note 2) V+ =2.8V to 6V (Note 1) £03 #05 mV + + +£0.05 +0.1 | % of DELTA V+ =6V to 15V (Note 1) +1 +3 mV + + +£0.05 +0.1 | % of DELTA Deadband Error (Note 3) V+ =2.8V to 6V (Note 1) +06 +1 mV + + +01 +0.2 | % of DELTA V+ =6V to 15V (Note 1) +2 +6 mV + + #01 £0.2 | % of DELTA los Input Current V+ =5V, Ty=25°C, OSC =GND +0.3 nA (Vin, SET POINT and DELTA Inputs) Fx | awh pat Ransance [Kemi Woe a) fe [| wa Tipat vonage ange SSSCS~—S@ | PSR [ Power SuppiyRange [ie | v 'scan) Power Supply ON V* =5V, Vpp ON 1.2 3 mA Current (Note 5) \\scorr) Power Supply OFF V* =SV, VppOFF = LTC1041C 0.001 0.5 uA Current (Note 5) LTC1041M 0.001 5 HA ON/OFF Output (Note 7) Vou Logical ‘'1"’ Output Voltage Vt =4.75V, loyr= —360pA 2.4 4.4 Vv Vor Logical ‘'0"’ Output Voltage | V*=4.75V, Igyr=1.6mA 0.25 0.4 Vv Rext Resistor Connected between V* andOSC Pin [@ | 100 10,000 ko fs Sampling Frequency Vt =SV, Ty= 25°C, Hz Rext= 1M Cex =0. pF The @ denotes the specifications which apply over the full operating Note 3: Deadband error = (Vy —V,)—2 x DELTA where Vy=upper band temperature range. The shaded electrical specifications indicate those limit and V_ = lower band limit. parameters which have been improved or guaranteed test limits provided Note 4: Ryy is guaranteed by design and is not tested, for the first time. Riy=1/(ts x 66pF). Note & Abples over input voltage range limit and includes gain Note 5: Average supply current =tp x Ision) xfs+(1—tp x fs) IsioFF)- inty. Note 6: Response time is set by an internal oscillator and is independent Note 2: SET POINT error= (YY*¥E) _ set pow of overdrive voltage. to=Vpp pulse width. ;

2 Note 7: Output also capable of meeting EIA/JEDEC standard B series

where V\\=upper band limit and V, = lower band limit. CMOS drive specifications. SS 6-70 LY Winer

TYPICAL PERFORMANCE CHARACTERISTICS Normalized Sampling Frequency vs V*, 'scony vs V* Temperature Sampling Rate vs Rext, Cext 2 22 N08 eg ey . LT 20 | PSS Hee ae Sie 3 2 ae asa Fat Pag 22° SS] NES Ze = 08 — EE SS

2 Ze [| To sc [4 J

tee) LL est J EP SSH 204 6 8 10 12 4 16 0 2 4 6 8 0 12 14 16 100k 1M 10M ‘SUPPLY VOLTAGE, V* (V) ‘SUPPLY VOLTAGE, V+ (V) Rent (2) Response Time vs Supply Voltage Response Time vs Temperature 110 130 Cet TT (cae SCOP eee 3» a 1 | | 1 Yt | ¢ Reerea 2, 1 TVET RECCCEEA = [HERE % 3 Att ETT eo Pee bz “COPE Er EEE a 4 6 8 10 12 14 16 ary -s 0 2 50 75 100 125 ‘SUPPLY VOLTAGE, V+ (V) AMBIENT TEMPERATURE, Ta (°C) Vpp Output Voltage vs Load Current Rin vs Sampling Frequency po Soo SC 206 ‘ x Sees teins tts eee eerie |

8 XQ ote 2 NEE

2 os BNSNE — = ST B12 SONS 2 Sa el So TS 2,LLLT Pi TTiry 8 i LOCC AT 6 12 3 4 5 6 7 8 9 1 10 102 103 104 LOAD CURRENT, Ic may ‘SAMPLING FREQUENCY. fg (Hz) LY lite 6-71

For Rs > 10kQ in the SET POINT and deadband is critical. These errors . may be defined in terms of Vy and VL. For source resistances greater than 10kQ, Cin cannot fully charge, causing voltage errors. To minimize theseerrors,an SET POINT error= (4) _ SET POINT input bypass capacitor, Cs, should be used. Charge is 2 shared between Cin and Cs, causing a small voltage error. deadband error=(Vu ~VL)—2. DELTA The magnitude of this error is AV=Vin x Cin/ (Cin +Cs). . a. This error can be made arbitrarily small by increasing Cs. The specified error limits (see electrical characteristics) . . include error due to offset, power supply variation, gain, The averaging effect of the bypass capacitor, Cs, causes time and temperature, another error term. Each time the input switches cycle between the plus and minus inputs, Cin is charged and —_ pulsed Power (Vpp) Output discharged. The average input current due to this is lave=Vin xCin xfs, where fs is the sampling fre- _ Itis often desirable to use the LTC 1041 with resistive net- quency. Because the input current is directly proportional + works such as bridges and voltage dividers. The power to the differential input voltage, the LTC 1041 canbe said © consumed by these resistive networks can far exceed to have an average input resistance of Rin=Vin/lave= __ that of the LTC 1041 itself. (fs x Cin). At low sample rates the LTC 1041 spends most of its time Since two comparator inputs are connected in parallel, off. A switched power output, Vpp, is provided to drive Rin is one half of this value (see typical curve of Rin ver- _ the input network, reducing its average power as well. sus fs). This finite input resistance causes anerrordueto Vep is switched to V+ during the controller’s active time the voltage divider between Rs and Rin. ( = 80ys) and toa high impedance (open circuit) when in- The input voltage error caused by both of these effects is ternal power is switched off 6 | Verror = Vin [2Cin/(2Cin +Cs)+Rs/(Rs +Rin)]. Figure 3 shows the Vpp output circuit. The Vpp output . _ _ voltage is not precisely controlled when driving a load we Verne A Sou o6G u). iM, Cs Vel (see typical curve of Vpp output voltage versus load cur- thot i por = 1V(66p! ad iv ities otice rent). In spite of this, high precision can be achieved in at most of the error is caused by Rin. if the sampling two ways: (1) driving ratiometric networks and (2) driv- frequency is reduced to 1Hz, the voltage error from the ing fast settling references input impedance effects is reduced to 136pV. , Input Voltage Range ve The input switches of the LTC 1041 are capable of switch- a ing either to the V+ supply or ground. Consequently, the | input voltage range includes both supply rails. This is a | j ues further benefit of the sampling input structure. f+e0,s--| +— COMPARATOR ON TIME ste ae [4] 7] Error Specifications a re The only measurable errors on the LTC1041 are the devi- ations from ‘‘ideal’’ of the upper and lower switching levels [Figure 1(b)]. From a control standpoint, the error Figure 3. Vpp Output Switch SRS A wire 6-73

TYPICAL APPLICATIONS ; Motor Speed Controller ve 100k 10k 1N4002 [J a > MOTOR* (+) @) i Oo ve 1.1k TI 2N6387 Pome Yo ml + DEADBAND SPEED “CANNON CKT26-TS-3SAE Battery Charger 16 | GE 1o68t our iN 1Naoo2 5Y a Wie Teas Re a ] = - ve 100Kn ‘LEAD = 36. 5k? “ol Penn 1nao02 2ko Eo 74c00 2.21k0 10K Cee ase EI rT 14002 130 - ° * * 1'SCR FIRES AT ZERO CROSSING —— “SET BATTERY VOLTAGE. BATTERY |S — MEASURED WITH ZERO CHARGE CURRENT. rr AT nee 6-75

PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. J Package

8 Lead Hermetic DIP

2.008 ren “Ee tomy | WAX 025 oes) WI] 1 fa mao TP 1 0220-0310 (5.988 ~7.874) 0.280 0.320 | (7378.13) a ET a 0.055 " oH ke wax MAX 0.015 ~0.060 oa6t= 1828) 0,008 0.018 ease (0.203 -0 460) ons 0385.2 0025 8.140.026 el pace 18 oaes=r 77 @a0e0256) Tmax 8A 150°C 100°C /W N Package

8 Lead Plastic

0.400 (10.160) aX [a] fs} [5]! Dp oe (6.350-£0.254) WeIoTY T7608 TB) Fear in e027 0.085, .020 ih ias09 i 08) 2.009 0.05 i ons f 2-038 oe +0025 0328 9.015, 0045+ 0.015 un TOE a32038h) Tmax eo” 110°C 150°C/W SS 6-76 7 OAM