C1237

UPC1237 NEC | Alldatasheet

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: ee Se ATA SHEET ee. ee or ee Een ee ee eee ee T¥EG& —CsCEtséBBIPOLLAR ANALOG INTEGRATED CIRCUIT oe PC1237 PROTECTOR IC FOR STEREO POWER AMPLIFIER

DESCRIPTION

uPC1237 is a monolithic integrated circuit designed for protecting stereo power amplifiers and loudspeakers,

FEATURES

© Work stably within a wide power supply voltage range. (Vcc = 25 to 60 V) © Contain a relay driver. (Max. Ig = 80 mA) © Work as either latching function or automatic resetting function by using pin 3. (In both overload detection and output offset detection, either function can be selected.) © Need only single power supply. © Both positive and negative output offset can be detected through the same pin. (Output offset detection through pin 2) © AC voltage can be detected. (For AC-power-OFF mute through pin 4) © The time delay from amplifier power ON to relay ON can be freely set by selecting external components. (For AC- power-ON mute through pin 7) @ The moment that amplifier-power is turned off, it can make relay broken OFF and then loudspeaker disconnected from amplifier to prevent a shock off noise.

ORDERING INFORMATION

Please refer to “Quality grade on NEC Semiconductor Devices” (Document number IEI-1209) published by NEC Corporation to know the specification of quality grade on the devices and its recommended applications, BLOCK DIAGRAM Voc mute 3 & 5 i = = 3s 3 2 e GND Document No. IC-1806A 7 : ~ : : : (0.D.No. 1C-7094A) Date Published October 1991 M - Printed in Japan © NEC Corporation 1986

ee oe — ee oe 0 as ae ee hr ABSOLUTE MAXIMUM RATINGS (T, = 25 °C) Power Supply Voltage Vec 60 v - Allowable Power Dissipation Pp 320° mW Operational Temperature Topt -20 to +75 °c Storage Temperature Tstg -40to+125 °C Pin 6 Maximum Current Ig max 80 mA Pin 4 Maximum Voltage V4max 10 v Pin 8 Maximum Voltage Vg max 8 v Pin 1 Maximum Current Iy max 3 mA Pin 2 Maximum Current Ig max +3 mA Pin 7 Maximum Voltage V7 max 8 v *Ta= 75°C RECOMMENDED OPERATING CONDITION Supply Voltage Vec= 25 to 45 to 60 V ELECTRICAL CHARACTERISTICS (Voc = 45 V, Ta = 25 °C, State using latching function) [___cuanAcTenistic | _svMaoc_ [win | Tve [ Max. | UNIT | CONDITION Pin 2 Positive Threshold Voltage Vtht2 [062 | 0.70 Pin 4 Threshold Voltage vih_ 4 0.90 [Fine Reference Voitge «| vai) ae)

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3 @ ® @sw3 0.0227 19 \\p2 uF t 35V Switch positions [venta [2p a [vee [2 ep [yea [2 sa Lvs | 2 | 3 [2 | TYPICAL APPLICATION CIRCUIT we (24 v, 37 ma ) oe Relay __ \\internal resistance 650 2 [ Aoos Feo} rot oO; | °| lo 1 QC] Speaker 1 i | i | | || | to | IL] Speaker R a | iu | 9° R AC100 V 15 kQ rt +Voc | if jteh]] Ren Wi! Cas y | | [ke Me | | | 27 330 uF + Z | | ! | WAI uF ) o| Mec? | [vec | 5 — = 60 Amplifier set @2—) © ©) @ 0.022 uF 71 (Automat) (Latch) L ae

POE EN" Se ig es aR ge Rea aT a a SANG ROT OS Od Sn ee TE eae AR LOGS Soo REN MReIe Naan AR nes ome ee Caley rc rE Pes camel Ee RAL ZR Say EONEC GPC1237 NOTE FOR USING uPC1237 1. FUNCTION FOR OUTPUT OFFSET DETECTION (pin 2) 1) If too much DC current flows through a speaker voice coil due to large output offset DC level, the voice coil might be overheated and the speaker might be broken. To prevent the damage, it is necessary to detect the Output Offset DC level and to disconnect the speaker from the power amplifier by breaking off a relay if the detected DC level is shifted beyond a threshold level. uPC1237 has a function to detect both the positive and the negative Output Offset DC level with its single power supply. As shown below, you can easily make the positive and the negative threshold level equivalent and also set up their level by choosing proper resistances, 2) How to determine the threshold levels of Output Offset detection. (+Vth) [1] The threshold level of positive output offset detection (+ Vth) is given by Eq. (1). R $Vth = (24-4) Vtht2, eee cc cccececececeeeseceesuseeesesecetesetesseceseseses (I) Re where Vth*2 is the original positive threshold level of pin 2, and vth*2 = 0.62 V TYP. [2] The threshold level of negative Output Offset detection (- Vth) is given by Eq. (2). - Ra -Vth == {-vth 2+ (24+) theo Ral, een nnnes 7) Re where Vth’ 2 is the original negative threshold level of pin 2, and Vth” 2=-0.17 V TYP. and Ica is the current from #PC1237 and, log = 12.5 pA TYP. at nearly ~ Vth. 3) You can easily find how to make + Vth level equivalent as shown below Ra _ R (2+—4)- vtht2 =~ { -vth 22+ Ay +i RAL, ne Ro Rc therefore determine Ra, Rg and Rc from Eq. (3) Attention; The original positive and negative threshold level at pin 2 without any resistances are unbalanced; +Vth = 0.62 V TYP. and ~ Vth =-0.17 V TYP. Example of design \\f you need the output offset threshold level +Vth to be +2.0 V, determine Ra, Rg and R¢ as shown below. [1] Substitute 2.0 to +Vth in Eq. (1) and obtain Ra/ Rc. Ra 2.0 = (2+—) X 0.62 Re Ra ——# 1,226 Re [2] Substitute - 2.0 to - Vth in Eq. (2) and obtain Ra (Rg) and Rc. Ra = 116.1 kQ Re = 94.7 kQ Therefore, if you need + Vth to be 2.0 volts, choose Ra, Rg and Rc as shown below. Ra = Rg = 120 kQ and Rc = 91 kQ. The lower limits of Ra and Rg are given by the maximum rating (t3 mA) of pin 2 and tV, SE <3 (mA) Ra(B) In case of recommended condition, that is Ra = Rg = 56 kQ and Rc = ~, + Vth can be obtained as shown below. 56 (kQ) Ve R, (1 tvth = (2+ 28K), 0.62 = 1.24 (Vv) iM Vin 56 (k2) 12 Re. Rp* (ime threshold level of ) [2] -Vth =-0.17 (2 +) -12.5 (uA) X 56 (kQ) = - 1.04 (V) Output offset detection, Ra=RB fig. 1 * Rch power amplifier output terminal is usually an imaginally GND as seen from Lch power amplifier, so that the equivalent circuit can be obtained as shown above.

1. FUNCTION OF AC LEVEL DETECTION When you turn off the power switch, it sometimes causes a shock-off noise, therefore it is necessary to break off the relay and then to keep the power amplifier apart from loud speaker at the moment that power switch is turned off. In other words, the protection circuit is required to have a function to detect that power-off time. However, in fact, it is difficult to detect that power-off time from actual DC supply voltage line. Because it cannot be turned 0 V instanta- neously due to a large capacitance inserted between the power supply line and GND. In case of uPC1237,it can detect this power-off time from AC power supply directly, that is, this is a function to detect AC level. The AC power supply level (usually 50 Hz or 60 Hz) can be transmitted to pin 4 through a half-wave rectification circuit as shown below. And it works within a wide range of AC level by choosing a proper resistance as R4 (Refer to the characteristic curve shown as fig.5 for the choice of R4). If power switch is turned off while the relay is being made ON and the speaker is being connected to the power amplifier output, the relay will be broken OFF to disconnect the speaker after a time delay (AC OFF mute) according to the discharge time constant determined by the voltage on pin 4, the external capacitance C4, and the internal resistance of the IC. Rq CAT 4.7 uF (*) fig. 2 3. FUNCTION OF OVERLOAD DETECTION (pin 1) The original threshold level of pin 1 is 0.67 V TYP. In case of using a constant-current drive, as the means of detection, the threshold current level is 110 uA TYP. When current which is larger than 110 uA flows to the IC, the relay will be broken OFF. Note; The overload detecting circuit is not included in the IC because of patent problems. Use the external circuit as an overload detection. 4. FUNCTION OF LATCHING AND AUTOMATIC RESETTING (pin 3) If the IC detects the abnormal condition such as the larger output offset level or the overload, the IC can make the relay broken OFF. And then, two functions can be selected after the condition returns to the normal state. One is that the relay is made ON automatically and the other is that it keeps the relay broken off until once the power switch is turned off and then is turned on again. The former is a function of automatic resetting and the latter is a function of latching, uPC1237 has both functions and can be selected either function by using pin 3. In case of latching, connect pin 3 to the ground through the capacitor, which is for preventing misoperation. For automatic resetting, connect it to the ground directly, This function is valid for both overload detection and output offset detection. 5. TIME DELAY FROM POWER AMPLIFIER POWER SWITCH ON TO RELAY ON (power-on mute at pin 7) To suppress shock-on noise generated by power ON, a time delay is provided by connecting a circuit with a time constant. This time delay is set to make relay ON to connect speakers after enough time for the power amplifier and the Preamplifier to reach a stable operating condition. The ON mute time is determined as follows, Va ~ V7 T (ON mute) = ~C7 + R7 + Ln ———,, Va where Vg is reference voltage at pin 8, 3.40 volts, TYP. and V7 is threshold level at pin 7, 2.06 volts, TYP. To pin 8 fig. 3 6. HOW TO MAKE IT WORK WITHIN A WIDE RANGE OF POWER SUPPLY VOLTAGE (pin 8) By choosing a proper resistance Rg connected to pin 8, the IC can work within a wide range of power supply voltage Veg from 25 to 60 volts. In case that pin 8 is directly driven by a regulated power supply, set Vg to 3.40 volts, TYP. As for the choice of Rg value, refer to the characteristic curve shown as fig.6. @— ove fig. 4

Be erg Se ae Re ee ee ere ee ee : SS Spee ak ee Sey eee De ee ene ay WOR oe See a a ae Tr rl rr Oe NE ieee fig. 5 OPTIMUM VALUE fig. 6 OPTIMUM VALUE OF EXTERNAL RESISTANCE Rq OF EXTERNAL RESISTANCE Rg Rg to Vac Characteristic Rg to Voc Characteristic “TTT TTT TTT] SESS eee COC See Sees aLLE EEE Clee eee ey LEE ae “TTEELELELLLI 14 [TT TTT rey eet | Ceecceeee oye EEE ee Fr CEEEEEE ELL Yee EE ee EEEEEEE VE? EER EEE] “CET TTT ATT COCR CECE EEE eee EP CEP ee ¢-EL PP TTA COE eee aE (CE ea See eee 20 30 40 50 6 THAT EEE PI APT TT yy Try PIAL LYE Pr rrr as oto 20 30 a0 80 60 Voc Vac — AC Supply Voltage (50 Hz)—Vr.m.s. Example) Use of E-24 series. Select 15 kQ Rg for 45 volts Vcc. Rq If no resistance of specified value is available, () choose a resistance which is as close as possible + to and lower than the value specified by the diagram. Cae 4.7 uF (10) Example) Use of E-24 series. Select 24 k2 Rg for 40 volts r.m.s. Vac. If no resistance of specified value is available, choose a resistance which is as close as possible to and lower than the value specified by the diagram.

TEMPERATURE CHARACTERISTIC Vg TON mut, Vth4, Vth+2, and Vth1 to Ta Characteristics J ee] Pit Py TTT pens xo s| ao of xg ee | > LL STP TPP errr yr rr | . & DSSS See 2,Jo jg | | CPE RES i oo | ELE Se | Pi PPT 1 [i ore er | ee | LEPE TT TTT AES =20 0 20 40 60 80 Ta—Ambient Temperature —°C

tO | N PO fo} x I] | | > | Cc Vv ze ][ (ays u Fi¢] G @ NOTE ITEM MILLIMETERS INCHES: Each lead centerline is located within 0.25 mm $f -——_—-——-— mum material condition 1.1 MIN. 0.043 MIN. 0.5'o" 0.027888 pu [zee | ot pm | sosmax. | 02 Max. | ee Q 5.75 MAX. U 1.5 MAX. 0.059 MAX. v 0.25? D2 | mn | ooes min, |

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