Low Current Preamplifier with Output Limiting GK504 - DATA SHEET FEATURES DESCRIPTION • designed to drive Class D integrated receivers The GK504 is Gennum’s proprietary low current preamplifier designed to drive the Class D series receivers. It consists of two independent single-ended, low noise inverting amplifiers, a symmetrical peak clipping, mid-supply referenced, transconductance output stage, and an on-chip microphone decoupling resistor. • adjustable peak clipper • low current drain • low noise and distortion Blocks A and B typically have an open loop voltage gain of 53 dB, with the closed loop gain set by the ratio of the feedback resistor to source impedance. It is recommended that the maximum closed loop gain be 20 dB lower than the open loop gain. All blocks of the device are internally bias compensated preventing any DC current flow via external feedback resistors. Without this compensation, audible scratchiness would be present during changes in Volume Control settings. It is acceptable to DC-couple blocks A and B of the device, however the third stage must be AC coupled in order to maintain DC bias requirements. • low external parts count • two low noise preamplifiers • transconductance output stage • mid supply referenced output • preamp A for Gain Trim or Telecoil STANDARD PACKAGING • 10 pin MICROpac The major advantage of the GK504 over other preamplifiers is the electronic MPO adjustment. Since conventional MPO is not possible in the class D receivers, it is provided electronically. The maximum output swing is easily set using an RMPO resistor. The receiver output level is thus limited, preventing it from exceeding the discomfort level. • 10 pin PLID® • 10 pin SLT • Chip ( 56 x 84 mils) Au Bump V MIC 3 R MIC 4 R A IN 2 A B P1 5 C 10 A OUT B IN 9 8 B OUT CIN 7 C OUT R 1 VB P2 6 R MPO GND U.S. Patent No.07/354,327 BLOCK DIAGRAM Revision Date; May 1998 Document No. 520 - 47 - 05 GENNUM CORPORATION P.O. Box 489, Stn. A, Burlington, Ontario, Canada L7R 3Y3 tel. +1 (905) 632-2996 Web Site: www.gennum.com E-mail: [email protected] ABSOLUTE MAXIMUM RATINGS PIN CONNECTIONS Parameter Value / Units Supply Voltage 5 VDC COUT Power Dissipation 25 mW VB -10°C to + 40°C VMIC CIN -20°C to + 70°C AIN BOUT Operating Temperature Storage Temperature AOUT 5 6 GND RMPO 10 1 BIN CAUTION CLASS 1 ESD SENSITIVITY ELECTRICAL CHARACTERISTICS Positive Current corresponds to current INTO the pin, Negative Current corresponds to current OUT of the pin, Conditions: Frequency = 1 kHz, VP - Pin voltage measured with conditions as shown in Test Circuit. Temperature 25o C. PARAMETER SYMBOL Supply Current IAMP Input Referred Noise IRN CONDITIONS MIN TYP MAX 165 240 315 µA 2 - µVRMS NFB 0.2 – 10 kHz at 12 dB/oct - UNITS Distortion THD - <1.0 - % On-Chip Microphone Resistance RMIC 3 4 5 kΩ -25 0 25 nA 500 590 650 mV 200 280 590 mV STAGES A and B Input Bias Current IBIAS Input Bias Voltage VBIAS RF=1M (Note 1) Output Swing Lo VOL RF=1M (Note 2) Max Output Current Capability IMAX -15 -30 -45 µA Open Loop Voltage Gain AVOL 46 53 - dB 14 16 18 dB - 0 2.5 dB -14.5 -12.5 -10.5 dBV 12 14 16 dB 19 24 29 KΩ OUTPUT STAGE Voltage Gain (Pin 8 to Pin 5) Gain Loss (Pin 8 to Pin 5) Maximum Output Level MPO Range Output Impedance AV ∆GAIN MPO ∆MPO VINAC = -52 dBV, RMPO= 0Ω VIN = -62 dBV, RMPO = 50k,Note 3 VINAC = -22 dBV, RMPO = 0Ω VINAC = -22 dBV,RMPO = (0 to 10k) ZOUT All parameters and conditions remain as shown in Test Circuit unless otherwise specified in Conditions column. NOTES: 1. IBIAS = (Vp(1,9 ) – Vp(1,9 )[RF=1M])/1M 2. VOL = VBIAS -Vp(1,9) [VIN DC=+1µA,RF=1M,IL=+15µA] 3. ∆GAIN = (V OUT / VIN [VIN =-62dBV, RMPO=0] )- (VOUT / VIN [VIN =-62dBV, RMPO=50k] 520 - 47 - 05 2 RMIC R IBIAS VIN DC IAMP P1 5 C B A 2 VB=1.3 VDC 4 3 0µ1 V OUT R P2 1 10 8 9 1µ0 I BIAS RF=0 6 7 RL 50k RMPO=10k RF=0 VINAC= 0VRMS 1kHz VINDC IL=0 IL=0 All resistors in ohms, all capacitors in µF, unless otherwise stated. Fig. 1 Test Circuit RMIC 3 4 48k 5 9 1 BASE CURRENT COMPENSATION 33k 2 10 48k 2.5k 6 7 All resistors in ohms, all capacitors in µF, unless otherwise stated. 8 Fig. 2 Functional Schematic 3 520 - 47 - 05 VB =1.3 VDC RMIC 1µ0 4 3 R P1 MIC CIN 0µ22 5 C B A 2 Class D Integrated Receiver 33n R 1µ0 P2 1 9 10 7 8 6 RMPO 10k 100k 100k 33n 10k R VC R GT All resistors in ohms, all capacitors in µF, unless otherwise stated. Fig. 3 Typical Hearing Instrument Application RMIC 1µ0 0µ47 VB =1.3 VDC 4 3 R Class D Integrated Receiver 5 C B A 2 P1 33n R 1 10 9 8 7 P2 1µ0 6 RMPO 10k - 100k R GT MIC + 0µ22 R VC All resistors in ohms, all capacitors in µF, unless otherwise stated. Fig. 4 520 - 47 - 05 100k 33n 10k Typical Hearing Instrument Application 4 VB =1.3 VDC RMIC 1µ0 RMIC 3k92 4 3 R CS 0µ22 5 C B A 2 P1 + BUFFER - 0µ1 R 1 AC SOURCE 50Ω 10 9 7 8 P2 RL 50k 6 R MPO =0 100k AC VOLTMETER 100k 0µ1 10k R VC R GT All resistors in ohms, all capacitors in µF, unless otherwise stated. This circuit as shown was used to generate the following graphs unless otherwise stated. Fig. 5 Characterization Circuit -5 -10 R VC = 100k -15 -18 R VC = 33k OUTPUT (dBV) OUTPUT (dBV) -25 -35 RMPO= 0 -14 -45 -55 R VC = 10kΩ -65 RMPO = 3.3k -22 R MPO = 10k -26 -30 -34 -75 R VC = 3.3kΩ -38 -85 -140 -120 -100 -80 -60 -40 -100 -20 -80 INPUT (dBV) -40 -20 Fig. 7 MPO for Various RMPO Values Fig. 6 I/O for Various RVC Values 2 10 CIN = 0.22µ 0 9 -2 8 CIN = 0.1µ -4 7 -6 THD (%) RELATIVE OUTPUT (dB) -60 INPUT (dBV) -8 CIN = 0.047µ -10 -12 5 4 3 CIN = 0.033µ -14 6 -16 2 -18 1 -20 20 200 2K 0 -90 20K -86 -82 -78 -74 -70 INPUT (dBV) FREQUENCY (Hz) Fig. 9 Distortion vs Input Level (RGT = RVC = 100k) Fig. 8 Frequency Response for Various CIN Values 5 520 - 47 - 05 10 -12 RELATIVE SUPPLY CURRENT (µA) -10 -16 OUTPUT (dBV) -30 -50 -70 -90 -20 -24 -28 -110 -32 -130 1 10 100 1k 10k -36 -50 100k -40 -30 RMPO (Ω) -20 -10 0 INPUT (dBV) Fig. 11 I/O for Amplifier C (as in Fig. 1) Fig. 10 Change in Supply Current vs RMPO 55 -10 50 -18 GAIN (dB) MAXIMUM OUTPUT (dBV) -14 -22 -26 1M 1M 10µ 45 1.3V -30 2.2k 10µ VOUT PREAMP 40 -34 VAC -38 -42 0 10 100 1k 10k 35 10 100k 100 1k 10k 100k FREQUENCY (Hz) RMPO (Ω) Fig. 12 Maximum Output vs RMPO (as in Fig. 1, VINAC= -15dBV) Fig. 13 Preamplifiers A and B Open Loop Voltage Gain DOCUMENT IDENTIFICATION: DATA SHEET The product is in production. Gennum reserves the right to make changes at any time to improve reliability, function or design, in order to provide the best product possible. REVISION NOTES: Updated to Data sheet Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. © Copyright July 1990 Gennum Corporation. All rights reserved. 520 - 47 - 05 6 Printed in Canada.