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Motorola Two Way Portable Radio Ht750ls Detailed 6881088c46 E Manual
Motorola Two Way Portable Radio Ht750ls Detailed 6881088c46 E Manual
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FMR-2045A-2December 26, 2003 VHF Theory of Operation: Frequency Generation Circuitry 71 Radio signal strength indicator, RSSI, a voltage signal, is used to drive Q3301 to saturation i.e. turned on. RSSI is produced by U3220 and is proportional to the gain of the RF amplifier and the input power to the radio. Resistors R3304 and R3305 are voltage dividers designed to turn on Q3301 at certain RSSI levels. In order to turn on Q3301 the voltage across R3305 must be greater or equal to the voltage across R3324, plus the base-emitter voltage (Vbe) present at Q3301. Capacitor C3209 is used to dampen any instability while the AGC is turning on. The current flowing into the collector of Q3301, a high current gain NPN transistor, will be drawn through the PIN diode to turn it on. Maximum current flowing through the PIN is limited by the resistors R3316, R3313, R3306 and R3324. C3326 is a feedback capacitor used to provide some stability to this high gain stage. An additional gain control circuit is formed by Q3201 and its associated circuitry. Resistors R3206 and R3207 are voltage dividers designed to turn on Q3201 at a significantly higher RSSI level than the level required to turn on PIN diode control transistor Q3301. In order to turn on Q3201 the voltage across R3207 must be greater or equal to the voltage across R3208, plus the base-emitter voltage (Vbe) present at Q3201. As current starts flowing into the collector of Q3201, it reduces the bias voltage at the base of IF amplifier transistor Q3200 and in turn, the gain of the IF amplifier. The gain can be controlled in a range of -30dB up to +10dB. 7.3 Frequency Generation Circuitry Figure 7-3. Frequency Generation Unit Block Diagram The Frequency Generation Circuitry is composed of two main ICs, the Fractional-N synthesizer (U3701), and the VCO/Buffer IC (U3801). Designed in conjunction to maximize compatibility, the two ICs provide many of the functions that normally would require additional circuitry. The synthesizer block diagram illustrates the interconnect and support circuitry used in the region. Refer to the relevant schematics for the reference designators. The synthesizer is powered by regulated 5V and 3.3V which come from U3711 and U3201 respectively. The synthesizer in turn generates a superfiltered 4.5V which powers U3801. In addition to the VCO, the synthesizer must interface with the logic and ASFIC circuitry. Programming for the synthesizer is accomplished through the data, clock and chip select lines from the microprocessor. A 3.3V dc signal from synthesizer lock detect line indicates to the microprocessor that the synthesizer is locked. Transmit modulation from the ASFIC is supplied to pin10 of U3701. Internally the audio is digitized by the Fractional-N and applied to the loop divider to provide the low-port modulation. The audio runs through an internal attenuator for modulation balancing purposes before going out to the VCO. Voltage Multiplier Synthesizer U3701 Loop Filter VCOBIC U3801 To Mixer To PA D r i v e rVCP Vmult1Aux3 MOD Out Modulating Signal Vmult2Rx VCO Circuit Tx VCOTRB 16.8 MHz Ref. Osc.Rx Out Tx Out Circuit
December 26, 2003FMR-2045A-2 72VHF Theory of Operation: Synthesizer 7.4 Synthesizer (Refer to the VHF Synthesizer Schematic Diagram on page 82.) The Fractional-N Synthesizer uses a 16.8MHz crystal (Y3761) to provide a reference for the system. The LVFractN IC (U3701) further divides this to 2.1MHz, 2.225 MHz, and 2.4 MHz as reference frequencies. Together with C3761, C3762, C3763, R3761 and D3761, they build up the reference oscillator which is capable of 2.5ppm stability over temperatures of -30 to 85 °C. It also provides 16.8MHz at pin 19 of U3701 to be used by ASFIC. The loop filter which consist of C3721, C3722, R3721, R3722 and R3723 provides the necessary dc steering voltage for the VCO and determines the amount of noise and spur passing through. In achieving fast locking for the synthesizer, an internal adapt charge pump provides higher current at pin 45 of U3701 to put synthesizer within the lock range. The required frequency is then locked by normal mode charge pump at pin 43. Both the normal and adapt charge pumps get their supply from the capacitive voltage multiplier which is made up of C3701 to C3704 and triple diodes D3701, D3702. Two 3.3V square waves (180 deg out of phase) are first multiplied by four and then shifted, along with regulated 5V, to build up 13.5V at pin 47 of U3701. Figure 7-4. Synthesizer Block Diagram DATA CLK CEX MODIN VCC, DC5V XTAL1 XTAL2 WARP PREIN VCP REFERENCE OSCILLATOR VOLTAGE MULTIPLIER VOLTAGE CONTROLLED OSCILLATOR 2-POLE LOOP FILTER DATA (U409 PIN 100) CLOCK (U409 PIN 1) CSX (U409 PIN 2) MOD IN (U404 PIN 40) +5V (U3711 PIN 4)7 8 9 10 13, 30 23 24 25 32 47 VMULT2 VMULT1BIAS1 SFOUTAUX3 AUX4 IADAPTIOUTGND FREFOUTLOCK4 19 6, 22, 23, 24 43 45 3 2 28 14 1540FILTERED 5VSTEERING LINE LOCK (U409 PIN 56) PRESCALER INLO RF INJECTION TX RF INJECTION (1ST STAGE OF PA) FREF (U3220 PIN 21 & U404 PIN 34) 39 BIAS2 41 DUAL TSTRS 48 5VR5 5, 20, 34, 36 (U3201 PIN 5) AUX1 VDD, 3.3VMODOUT U3701 LOW VOLTAGE FRACTIONAL-N SYNTHESIZER
FMR-2045A-2December 26, 2003
VHF Theory of Operation: Voltage-Controlled Oscillator (VCO) 73
7.5 Voltage-Controlled Oscillator (VCO)
(Refer to the VHF Voltage-Controlled Oscillator Schematic Diagram on page 83.)
Figure 7-5. VCO Block Diagram
The VCOBIC (U3801) in conjunction with the Fractional-N synthesizer (U3701) generates RF in both
the receive and the transmit modes of operation. The TRB line (U3801 pin 19) determines which
oscillator and buffer will be enabled. A sample of the RF signal from the enabled oscillator is routed
from U3801 pin 12, through a low pass filter, to the prescaler input (U3701 pin 32). After frequency
comparison in the synthesizer, a resultant CONTROL VOLTAGE is received at the VCO. This
voltage is a DC voltage typically between 3.5V and 9.5V when the PLL is locked on frequency.
Presc
RX
TXMatching
NetworkLow Pass
Filter
Attenuator Pin8
Pin14
Pin10(3701 Pin28)
VCC Buffers
TX RF Injection U3701 Pin 32 AUX3 (U3701 Pin2)
Prescaler Out
Pin 12 Pin 19 Pin 20
TX/RX/BS
Switching Network
U3801
VCOBIC
Rx
Active Bias
Tx
Active Bias
Pin2
Rx-I adjustPin1
Tx-I adjustPins 9,11,17
Pin18Vsens
Circuit Pin15Pin16 RX VCO
Circuit
TX VCO
Circuit RX Tank
TX TankPin7
Vcc-Superfilter
Collector/RF in
Pin4
Pin5
Pin6
RX
TX
(U3701 Pin28)Rx-SW
Tx-SW
Vcc-Logic
(U3701 Pin28) Steer Line
Voltage
(VCTRL)Pin13
Pin3TRB_IN
LO RF INJECTION
VSFVSF VSF
December 26, 2003FMR-2045A-2 74VHF Theory of Operation: Voltage-Controlled Oscillator (VCO) The RF section of the VCOBIC(U3801) is operated at 4.54 V (VSF), while the control section of the VCOBIC and Fractional-N synthesizer (U3701) is operated at 3.3V. The operation logic is shown in Table 7-1. In receive mode, U3801 pin 19 is low or grounded. This activates the receive VCO by enabling the receive oscillator and the receive buffer of U3801. The RF signal at U3801 pin 8 is run through a matching network. The resulting RF signal is the LO RF INJECTION and it is applied to the mixer at T3302. During the transmit condition, when PTT is depressed, 3.2 volts is applied to U3801 pin 19. This activates the transmit VCO by enabling the transmit oscillator and the transmit buffer of U3801. The RF signal at U3801 pin 10 is injected into the input of the PA module (U3501 pin16). This RF signal is the TX RF INJECTION. Also in transmit mode, the audio signal to be frequency modulated onto the carrier is received through U3701 pin 41. When a high impedance is applied to U3801 pin 19, the VCO is operating in BATTERY SAVER mode. In this case, both the receive and transmit oscillators as well as the receive transmit and prescaler buffer are turned off.Table 7-1. VCO Control Logic Desired Mode AUX 4 AUX 3 TRB Txn.u.High (@3.2V)High (@3.2V) Rx n.u. Low Low Battery Savern.u.Hi-Z/Float (@1.6V)Hi-Z/Float (@1.6V)
Chapter 8 VHF Circuit Board Layouts, Schematic Diagrams and Parts List 8.1 Notes For All Schematics and Circuit Boards * Component is frequency sensitive. Refer to the Electrical Parts List for value and usage. 1.Unless otherwise stated, resistances are in Ohms (k = 1000), and capacitances are in picofarads (pF) or microfarads (µF). 2.DC voltages are measured from point indicated to chassis ground using a Motorola DC multime- ter or equivalent. Transmitter measurements should be made with a 1.2 µH choke in series with the voltage probe to prevent circuit loading. 3.Reference Designators are assigned in the following manner: 400/500 Series = Controller 600 Series = Keypad Board 3200 Series = IF Circuitry 3300 Series = Receiver 3500 Series = Transmitter 3700 and 3800 Series = Frequency Generation 4.Interconnect Tie Point Legend: UNSWB+ = Unswitch Battery Voltage (7.5V) SWB+ = Switch Battery Voltage (7.5V) R5 = Receiver Five Volts CLK = Clock Vdda = Regulated 3.3 Volts (for analog) Vddd = Regulated 3.3 Volts (for digital) CSX = Chip Select Line SYN = Synthesizer DACRX = Digital-to-Analog Voltage (for Receiver Front-End Filter) VSF = Voltage Super Filtered (5 volts) VR = Voltage Regulator SIX-LAYER CIRCUIT BOARD DETAIL VIEWING COPPER STEPS IN PROPER LAYER SEQUENCE LAYER 1 (L1) LAYER 2 (L2) LAYER 3 (L3) LAYER 4 (L4) LAYER 5 (L5) LAYER 6 (L6) INNER LAYERS SIDE 1 SIDE 2
December 26, 2003FMR-2045A-2 This Page Intentionally Left Blank 76VHF Circuit Board Layouts, Schematic Diagrams and Parts List: Notes For All Schematics and Circuit Boards
Circuit Board/Schematic Diagrams and Parts List 77 FMR-2045A-2 December 26, 2003 8.2 Circuit Board/Schematic Diagrams and Parts List Figure 8-1. VHF (136-174MHz) Main Board Top Side PCB No. 8486473Z03 C502C505 C512 C513 Q502Q505 R505R506 VR501 123 5PB501 4 3 2 Y3204C521 C3225C3278 R3275 58 U3221 VR440 2 Y3202 Y3205 C3208 R3205 R3208 R3211 4C3206 L3200 L3203 123 5PB504VR444 43 2 Y3203 C3201 C3202 SH3203 2 3 4 56 Y3200123 5PB502 C522 B503B504 TP3701C523 123 5PB503 6 431 Y3761 C432 TP3702 C3706 C3710 C3711 C3712 C3713 C3714 C3715 C3721C3722 C3724 C3741 C3742 C3743 C3744 C3745 C3746 C3752 C3753 C3754 4 3Q3721 R3701 R3721R3722 R3723R3741 R3751 R3752 SH3701 U3711 TP3301 C3318 C3320 C3334 C3335 L3309 L3312 R3318 R3321 R3322 R3323 SH3302 3 T3301 6 4 3 T3302 C3329 R3317 6 4 C3306 C3307 C3308C3309 C3310 C3311 C3312 C3313C3314 C3327C3330 C3331 C3332 C3338 CR3303 D3302 L3304 L3305 L3306 Q3302 R3308 R3309 R3310 R3311 R3312R3313 R3316SH3303 C3319 C511 C514 C520 43 2CR503 R501 R502C3537 C3539 L35381 2 3 5 PB505 SH3501 C3524 C3525 C3528 C3531 C3532 C3533C3534 C3535 C3536C3550 C3551 C3552 D3521 D3551 L3531 L3532L3551 L3552 R3551 C3514 C3517 C3518 C3519 C3521 C3523 C3527 C3546 C3547 L3515 L3518 L3521 L3522 1 2 3 Q3501 R3512R3513 R3544 R3545 R3546R3547 R3548 SH3502C3512 C3513 L3511 L3512 L3504 L3513 R3506 R3507 R3541 C3501 C3502 C3503 C3504C3505 C3541 C3542 C3543 C3544 L3501L3503 R3501R3502 R3503 R3505R3542 R3543 1 168 9 U3501 C3822 C3824C3825 C3826 C3828 C3829C3830C3832 C3833 C3834 C3835 C3836 C3842 D3821 D3831 D3832 L3821 L3822L3823L3824 L3825L3831 L3832 L3833L3834 R3821 R3822 R3823R3828 R3833 R3834 R3835 R3836 SH3801 C400 C401C402 C403C467 C480 C482CR412 CR440 Q400 Q403 43 Q405 R401 R402R403R405 R406 R407R416R427 R447 R448 R451 R452R453 R454 R455 R456 R476 R481 SH4014 5 8U400 C441 C471 C472 C473 C490 C491 C492 C493 C494 C495 C496C497 CR413 22 20121 J403 L40043 Q417 R421 R450 R477 TP405 TP406 TP415 VR434 VR450 C427 C443 C444 L401 R435TP401 TP402 TP410 VR447 VR449 C428 RT400 SH40040 C424C425 C426 C429 R408R428 R429 R478 R49222 7 1 161 1 45 8 U407 R418 21 8 U405 U406 C423 E407 E408 E409 R410 R437 32 17 1 J400
78Circuit Board/Schematic Diagrams and Parts ListDecember 26, 2003FMR-2045A-2 Figure 8-2. VHF (136-174MHz) Main Board Bottom Side PCB No. 8486473Z03 C449 C458 C459C463 C466C4020C4021 E400 E401 E402E403 E404 E405 E406 1 7651 26 U409 C453 C456 L410 L411R409R411 R432 R457C431 C433 C436C437 3 FL401 R414 R415 R420 R426R463 C434C435 CR411 Q416R419 R460 R461R462 SH402 U410C328 C359C390 C3763D3761R373 R374R375 R377 R3781 4 5 8 U303 VR442 C3212 R3214 R3215 R3761 U3201 C337C358 C383 C3213C3215 CR501L505 R370 R371 R372 R376 VR439 VR441 VR506 C442 C445C483 C484R473VR432 VR433 VR448 C450 C452 C476 C478 43 Q410 R471 11 1 20 10U420 137 25 13U404 C475 C477R431 C416 C422 C447 C448 C474R400R423R424 R472 R498R499 C407C419 C420 C421 C479 C481R413 R425 R445 R449 R475 C408 C409 C410C411 C414 C415 C430 C440 C446 R434R436 SH403 VR460 C451C3701 C3702 C3703 C3704 C3705 C3707 C3708 C3709 C3725 C3731 C3732 C3733 C3734 C3761 C3762 D3701 D3702L3731 R3702R3703 R3704 R3705 R3726 R3762 SH3702 1 37 25 13 U3701 C3726 C3727 C3755L3701 R3727 C3815 C3816 C3818 C3827 L3813 L3816R3812 R3816R3817 R3818 R3829R3830 R3831 R3832 111 20 U3801 C3812 C3801C3802 C3803 C3804C3805 C3806 C3808 C3810C3813 C3821C3823 L3801 L3809L3811 L3812L3826 Q3801 R3801R3802 R3803 R3804 R3805R3806 R3807 R3808 R3824R3825R3826 SH3802 10 C3809 C3811 R3811 3 21 B501 C503 C535 F501 C3336 L3519 C3508 C3509 C3561 C3562 C3566 C3567 Q3561 R3561R3562 R3563 R3564 R3570 1 25 U3503C3560 C3563C3564 C3565 C3568 C3570 C3571 H3501 R3565 R3569 17 9 U3502 C3526 C3569 L3523 R3566 R3571R3572 R3573 TP3502 C3515C3516 R3519 VR3501C3315 C3316 C3317 C3337C3339CR3301 L3308 R3301 R3304 R3305 R3319 R3320RT3301 234 1J3501 J3502 2 C 8 C 4 S501 4 5 32 S502 C3301 C3302 C3303 C3304 C3305 C3321 C3322C3323C3324 C3325 C3326 CR3302D3301 L3301 L3303 Q3301 R3303 R3306 R3307R3314 R3315 R3324SH3301 C3200 C3205C3207C3209 C3210 C3218 C3221 C3222C3226 C3228 C3230 C3231 C3232 C3233 C3234C3236 CR3201 CR3202 CR3203 L3202 Q3200 R3200 R3201 R3202 R3203R3204 R3209 R3212 R3213 R3220 R3221 R3222 R3223R3224 11 1 2010 U3220 C3203 C3238C3274 C3275 C3279 L3270 Q3270 R3206 R3207 R3226R3270R3271 R3273R3274 R3276 SH32024 3 2 Y3201
Circuit Board/Schematic Diagrams and Parts List79FMR-2045A-2December 26, 2003 Figure 8-3. VHF Controls And Switches Schematic Diagram VOL MECH_SWB+ Vdda 6.8VVR501 HIGH TAB1 6 TAB2 7 2 mgc_comps 4 1LOW5 3S502 C502 0.47uF C505100pF UNSWB+ 1000pF1000pFC535 100pFC503 CR501VR439 10V2 124V F501 BATT_CODE SB1 EMER LI_ION VR506 6.8VL505 390nHB501 DATA NEG POS B503 B504.01uFC520 .01uFC521 1 2SWITCHPB505 VR440 NU6.8V PB501 1 2 SWITCH PB504 1 2 SWITCH NU 6.8V VR444 PTT PB502 1 2 SWITCH VR441 NU6.8VC522 .01uF SB2 PB503 1 2 SWITCH NU6.8V VR442 C523 .01uF SB3 M100 M101 SWB+Vdda4 347K R506 R505 10K Q505 5 1 6 2Q502 switch RED_LED R501 680680 CR503 24 13R502 180 180 RTA2 RTA0 RTA1 RTA3 S501 SWITCH GND1 PC0 PC1 PC2 PC3 C0 C1 GND 1 2 48 C0 C1 9 7 100pFC511 C512 100pF C513 100pF 100pFC514 oswitch GREEN_LED
80Circuit Board/Schematic Diagrams and Parts ListDecember 26, 2003FMR-2045A-2 Figure 8-4. VHF Receiver Front-End Schematic Diagram G UNSWB_PLUS_1_RX C3336 10uF UNSWB+UNSWB_PLUS_2_RX G L3301 12nH RX_INC3302 150pF RX_IN_1_FE 5.6pF C3301C3303 15pF D3301CR3303 L3303 12nHC3304 150pF 33KR3307 NU C3305 NU C3326 470pFC3338 470pF R3304 100KR3308 1.5K R3311 NU 7.5K R3309 5.1 R3312 0.1uF C3306 Q330239 R3313 L3304 470nH R3315 330 C3308 330pF 100pF C3307 2.7K R3310 16pF C3312 150pF C3311 R3314 27 D3302 NU C3310L3305 12nH12nH SMBV1032SMBV1032CR330210nH L3308 C3317 30pF C3316 3.3pF10pF 12nHC3315 L3306 NU C3314 150pF C3313 10pF C3339C3318 .022uF NU C3319RF BALUN 46 3 1 2 T3301 R3320 NU 1 CR3301 23 4 R3319 NUG L3309 150nH IF_1_FE 0 R3323R3322 R3321 51 IF C3320 82pF NU GR5_2_FE C3309 0.1uF0.1uF 470470R3316 .022uF C3337R5_3_FE R5 G G DACRx_1_FE RX_INJ RX_INJ_1_FE DACRx DUMMY G C3324 33pF R3303 100K C3321 330pF RSSIRSSI_1_FE C3322 100pFC3323 100pFR3305 68K NU RT3301220 R3324 220 R3301 NUQ3301R3306 2.2K C3325 1000pFC3327 330pF 100pF C3330 100pF C3331 39pF 100K C3332 R3317 330pF C3329 SH3302 1 SHIELD SHIELD SH3301 11SHIELD SH3303 TP33011 R3318 470L3312 33nH 20pF C3335 22pF C3334 4 6 3 1 2 T3302 IF BALUN