Siemens MGM3000X Datasheet

Video Modulator for
FM/AM-Audio

Features

● FM- and AM-audio modulator

● Audio carrier output for suppression of harmonics

● Sync level clamping of video input signal

● Controlling of peak white value

● Continuous adjustment of modulation depth for

positive or negative values

● Symmetrical mixer output with separate ground area

● Symmetrical oscillator with separate RF-ground

● Low spurious radiation

● High stability of the RF-oscillator frequency

● High stability of the audio oscillator

● Internal reference voltage

● 12 V supply voltage

MGM 3000X

Bipolar IC

P-DSO-20-1

Type Ordering Code Package

MGM 3000X Q67000-A5179 P-DSO-20-1 (SMD)
MGM 3000X Q67006-A5179 P-DSO-20-1 Tape & Reel (SMD)

Functional Description and Application

The monolithic integrated circuit MGM 3000X is especially suitable as a modulator for
the 48 to 860 MHz frequency range.
Video recorders, cable converters, TV-converter networks, demodulators, video
generators, video security systems, amateur TV-applications and personal computers.

Circuit Description
Oscillator

The RF-oscillator is available at pins 3 - 7. The oscillator operates as a symmetrical
Colpitts circuit. The oscillator chip ground, pin 5, should be connected to ground at the
resonance circuit shielding point. An external oscillator can be injected inductively or
capacitively via pins 3 and 7. The layout of the PCB should be such as to provide a
minimum shielding attenuation between the oscillator pins 3 - 7 and modulator output
pins 15 - 17 of approximately 80 dB.

Semiconductor Group 1 12.94

MGM 3000X

For optimal residual carrier suppression, the symmetrical mixer outputs at pins 15, 17
should be connected to a matched balanced-to-unbalanced broadband transformer, e.g.
a Guanella transformer with good phase precision at 0 ° and 180 °. The transmission
loss should be less than 3 dB. In addition, an LC-low pass filter combination is required
at the output. The cut-off frequency of the low pass filter combination must exceed the
maximum operating frequency.

Video

The video signal with the negative synchronous level is capacitively connected to pin 12.
The internal clamping circuit is referenced to the synchronizing level. Should the video
signal change by 6 dB, this change will be compensated by the resonance circuit which
is set by the peak white value. At pin 13, the current pulses of the peak white detector
are filtered through the capacitor which also determines the control time constant. The
RF-carrier switches from negative to positive video modulation, when pin 14 is
connected to ground. By varying the value of resistance
the modulation depth can be increased from 70 % to 100 % when the modulation is
negative and decreased from 100 % to 70 % when the modulation is positive.

R at pin 14 between ∞ …0Ω

Audio

Via pin 1, the audio signal is capacitively coupled to the AF-input for the FM-modulation
of the oscillator. A parallel resonance circuit is connected to the audio carrier oscillator
at pins 19, 20. The unloaded
resistor

R

= 6.8 kΩ to ensure a video to audio carrier ratio of 12.5 dB. At the same time,

T

Q of the resonant circuit must be Q = 25 and the parallel

capacitative and/or inductive reactance for the resonance frequency should have a value
of

X

≈ XL≈ 800 Ω.

C

Via pin 18, the audio signal is capacitively coupled to the AF-input for the AM-modulation
of the oscillator. This signal is forwarded to a mixer which is influenced by the AM­modulation input of pin 18. The video to audio carrier ratio can be changed by connecting
an external voltage to pin 18, which deviates from the internal reference voltage.
Through an additional external dc voltage at pin 18, the set AM-modulation index can be
changed by overriding the internally adjusted control voltage for a fixed AM-modulation
index.

At the output of the above described mixer the FM and/or AM modulated audio signal is
added to the video signal and mixed with the oscillator signal in the RF-mixer.

For optimal suppression of harmonics of the audio carrier an audio filter should be
connected between pin 10 and 11.

Source

The internal reference voltage is available at pin 2 and has to be capactively blocked
there.

Semiconductor Group 2

Pin Configuration

(top view)

MGM 3000X

Semiconductor Group 3

Pin Definitions and Functions
Pin No. Symbol Function

1 FM-Audio AF-input for FM-modulation

MGM 3000X

2

V

REF

Internal reference voltage (7.5 V)
3 OSC-Input 1 Symmetrical oscillator input
4 OSC-Out 1 Symmetrical oscillator output
5 OSC-Ground Oscillator ground
6 OSC-Out 2 Symmetrical oscillator output
7 OSC-Input 2 Symmetrical oscillator input
8

V

S

Supply voltage (12 V)
9 N.C. Not connected
10 Audio Out 1 Audio output; symmetrical inputs for audio filter
11 Audio Out 2 Audio output; symmetrical inputs for audio filter
12 Video Video input with clamping
13 Video-Cap. Connection for smoothing capacitor for video control loop
14 Modulation Switch-over for positive and negative modulation
15 Output 2 Symmetrical RF-output
16 Ground Ground
17 Output 1 Symmetrical RF-output
18 AM-Audio Video to audio carrier ratio adjustment and AF-input for

AM-modulation
19 FM-Audio OSC FM-audio oscillator, symmetrical inputs for tank circuit
20 FM-Audio OSC FM-audio oscillator, symmetrical inputs for tank circuit

Semiconductor Group 4

MGM 3000X

Block Diagram

Semiconductor Group 5

Absolute Maximum Ratings

T

= 0 to 70 °C

A

Parameter Symbol Limit Values Unit Remarks

min. typ. max.

MGM 3000X

Supply voltage pin 8
Current from pin 2 −

Voltage at pin 1
Voltage at pin 2
Voltage at pin 12

Capacitance at pin 2
Capacitance at pin 13

Voltage at pin 14
Voltage at pin 15
Voltage at pin 17
Voltage at pin 18

V

V
V
V

C
C

V
V
V
V

S

1
2
10

14
15
17
18

2
13

− 0.3 14.5 V

I

2

0 2mAV

0
6
0

0
0

− 0.3

V

2

V

2

V

− 1.5

2

2

8.5

1.5
100

15

1.4

13.5

13.5

V

+ 1.5

2

V
V
Vpp only via

nF
µF

V
V
V
V

= 7-8 V,

2

V

= 10-13.5 V

S

V

= 10-13.5 V

S

C (max.1 µF)

According to the application circuit, only the provided circuitry can be connected
to pins 3, 4, 6, 7, 10, 11, 18 and 20.

Junction temperature

T

j

150 °C
Storage temperature
Thermal resistance

T
R

stg

th

– 40 125 °C

Operating Range

Supply voltage
Video input frequency
Audio input frequency
Output frequency

Ambient temperature

Semiconductor Group 6

V
f

Video

f

AF

f

Q

T

S

10 13.5 V
0 6 MHz
0 20 kHz
30 860 MHz depending on the

A

080°C

80 K/W

oscillator circuitry at
pins 3-7

Absolute Maximum Ratings (cont’d)

T

=0to70°C

A

Parameter Symbol Limit Values Unit Remarks

min. typ. max.

MGM 3000X

Audio oscillator f
Voltage at pin 2

Voltage at pin 15, 17

OSC

V
V

2
15, 17

4 7 MHz
7

V

2

7.50

V

S

V
V

AC/DC Characteristics

T

=25°C; VS=12V

A

Parameter Symbol Limit Values Unit Test Condition Test

Circuit

min. typ. max.

Source

Current consumption
Current consumption

Reference voltage V

Oscillator

I

8

I

+ I

15

2

15

2.0

17

20

2.6

26

3.4

mA
mA

I

= 0 mA 1

2

7.00 7.25 7.50 V 0 ≤ I2≤ 1mA 1

Oscillator frequency

f

OSC

30 860 MHz external circuitry

range
Switch-on, warm up

∆f

OSC

drift TC-value of
capacitor in osc.
circuit is 0; drift is

0
0

–50

– 200
referenced only to
selfheating of the
component.

Frequency drift as
function of V

S

RF-output

∆f

R

OSC

15

; R

– 150 150 kHz VS= 10-13.5 V

10

17

impedance

C

; C

15

0.5 1 2.0

17

Semiconductor Group 7

– 500
– 500

kHz
kHz

kΩ

pF

adjusted to frequency

t = 0.5-10 s;
T

= const.

A

Ch 30
Ch 40

T

= const.; Ch 40

A

parallel equivalent
circuit
parallel equivalent
circuit

1
1

1

1

1