MITEL SL3522 Datasheet

SL3522

500MHz 75dB Logarithmic/Limiting Amplifier

Advance Information

Supersedes edition in Professional Products IC Handbook May 1991 DS3534 - 2.0 April 1994

The SL3522 is a monolithic seven stage successive
detection logarithmic amplifier integrated circuit for use in the
100MHz to 500MHz frequency range. It features an on–chip
video amplifier with provision for external adjustment of log
Slope and offset. It also features a balanced RF output. The
SL3522 operates from supplies of ±5V.

FEATURES

■ 75dB Dynamic Range

■ Surface Mount SO Package

■ Adjustable Log Slope and Offset

■ 0dBm RF Limiting Output

■ 60dBm Limiting Range

■ 2V Video Output Range

■ Low Power (Typ. 1W)

■ Temperature Range (T

): -55°C to +125°C

CASE

RF O/P GND

RF O/P–
RF O/P+

RF O/P V

VIDEO O/P V

VIDEO O/P

VIDEO O/P V

N/C
N/C
V

GND

V

GND

V

EE

EE

EE

EE
EE

CC

128
2
3
4
5
6
7
8

9
10
11
12
13
14

Fig.1 Pin connections - top view

27
26
25
24
23
22
21
20
19
18
17
16
15

RF I/P+
RF I/P–
V

EE

GND
V

EE

GND
V

EE

GND
VIDEO V

EE

GAIN ADJUST
TRIM REF
OFFSET ADJ
VIDEO GND
VIDEO V

CC

MC28

APPLICATIONS

■ Ultra Wideband Log Receivers

■ Channelised and Monpulse Radar

■ Instrumentation

ABSOLUTE MAXIMUM RATINGS

Supply Voltage ±6.0V
Storage temperature -65°C to +175°C
Junction temperature +175°C
Thermal resistance

Die-to-case 15.5°C/W

Die-to-ambient 76.5°C/W
Applied DC voltage to RF input ±400mV
Applied RF power to RF input +15dBm

RF

27

I/P –

RF
I/P +

28

ORDERING INFORMATION

SL3522 A MC (Miniature Ceramic package)
SL3522 C MC (Miniature Ceramic package)
SL3522 NA 1C (Probe-tested bare die)

(Also available: SL3522 AA MC screened to Mitel HI-REL
level A. Contact Mitel Semiconductor sales outlet for a
separate datasheet.)

ESD PROTECTION

To achieve the high frequency performance there are no
ESD protection structures on the RF input pins (27, 28). These
pins are highly static sensitive, typically measured as 250V
using MIL-STD-883 method 3015. Therefore, ESD handling
precautions are essential to avoid degradation of
performance or permanent damage to this device.

RF

RF

O/P–

91014

VIDEO GAIN

AND OFFSET

O/P+

ADJUST

O/P
V

CC

16

13
12

15

O/P

GND

VIDEO

OUT

O/P
V

EE

VIDEO

V

CC

3, 5, 7, 20, 22, 24, 26 V

4, 6, 8, 21, 23, 25 GND

EE

Fig.2 Functional block diagram

19 18 17

GAIN

ADJ

RTR

R

G

OFFSET

O

ADJ

SL3522

ELECTRICAL CHARACTERISTICS

The electrical characteristics are guaranteed over the following range of operating conditions, using test circuit in Fig. 3 (unless
otherwise stated):

Temperature range: Military: SL3522 A MC, SL3522 NA 1C 55°C to +125°C (T

Commercial: SL3522 C MC 0°C to +70°C (T

CASE

Supply voltage: VCC: +4.50V to +5.50V (all grades)

VEE: -4.5V to -5.50V (all grades)
Frequency =100MHz to 500MHz
Rg, Ro, Rt =1.5KΩ
Video output load =200Ω//20pF

Test conditions (unless otherwise stated):

Temperature: SL3522 A MC: +25°C, +125°C & -55°C (T

CASE

)
SL3522 C MC: +25°C
SL3522 NA 1C +25°C

Supply voltage: VCC = +5.0V, VEE = -5.0V

Parameter

Pin

Value

Units

Conditions

Min. Typ. Max.

Positive supply current

14, 15

28

35

mA

V

CC

= +5.0V
(quiescent)
Negative supply current
(quiescent)
Dynamic range

Linearity

Video output range
Video slope
Video slope variation
Video slope adjust range
Video offset
Video offset variation
Video offset adjust range
Video trim reference
voltage
Video output impedance
Video rise time

ALL V

Pins

13
13
13
13
13
13
13

17, 18,

19
13
13

EE

75
70

-1

-1

-1.25

1.30
18

-5

±20

-0.1

±0.5

-0.59

150
180

1.75
21

±30

+0.25

-05

-0.54

10
16

175
210

+1
+1

+1.25

2.00
24
+5

+0.5

-0.49

mA
mA

dB
dB
dB
dB
dB

V

mV/dB

%
%
V

mV/°C

V
V

Ω

ns

= -5.0V See note 1

V

EE

V

= -5.0V See note 2

EE

100 to 400MHz See note 1, 3
See note 1, 4
T

= -55°C

CASE

T

= +25°C

CASE

T

= +125°C

CASE

See note 5
RG = 1kΩ to 2.2kΩ

= +25°C

T

CASE

RO = 1kΩ to 2.2kΩ

See note 8
10% - 90% (60dB step)

See note 7
Input VSWR
RF bandwidth

27, 28

9, 10

1.5:1
450

MHz

Zs = 50Ω See note 7
TCASE = +25°C RFIN = -70dBm

See notes 2, 7
RF limiting range
RF limited output level

9, 10
9, 10

-3.0

60

-1.0

+1.0

dB

dBm

See notes 2, 6, 7

R1 = 50Ω single ended

See note 2
RF output impedance

9, 10

50

Ω

Single ended See notes 2, 8

CASE

)

)

2

ELECTRICAL CHARACTERISTICS (cont.)

Parameter

Pin

Value

Min. Typ. Max.

Units

SL3522

Conditions

Phase variation with RF
Input level
Phase tracking between
units

15

Degrees

3

Degrees

Freq = 300MHz RF

See notes 2, 7

T

= +25°C FREQ = 300MHz

CASE

See notes 2, 7

= -60 to +10dBm

IN

Notes

1 RF output buffer OFF (pin 8 disconnected from 0V)
2 RF output buffer ON (pin 8 connected to 0V)
3 Minimum dynamic range under any single set of operating conditions
4 Log linearity guaranteed for pin = -64dBm to +6dBm for ALL supply, temperature and frequency conditions
5 Full range of supply, temperature and frequency conditions
6 Input limiting range typically -50dBm to +10dBm
7 Not tested, but guaranteed by characterisation
8 Not tested, but guaranteed by design

The SL3522 CANNOT be GUARANTEED to operate below 100MHz and meet the electrical characteristics shown above.
However, characterisation has shown that the device can still function adequately down to frequencies of 50MHz, with the following
reservations:-

1)The video bandwidth is fixed to approx 40MHz a certain amount of carrier breakthrough on the video O/P (pin 13) will occur,

with input signal frequencies below 100MHz.

2)There are 2 RF coupling capacitors (20pF) on-chip, which couple the output signal from stage 3 to the input of stage 4 (ref

Fig. 24). These can introduce undesirable limiting phase performance for input signal frequencies below 100MHz.

RF INPUT

123

ANZAC

TP101

654

L1

10n

L2

GAIN
ADJUST
R

2k2

G

10n

R

1k5

T

OFFSET
ADJUST

2k2

R

0

+5V V

CC

262728

321

10n

+5V V

EE

NOTES

1. Inductors L1 to L5 = 3 TURNS

2. D.U.T. mounted in a test socket

3. Transmission line BALUNS used

30SWG on Ferrite bead.
– ENPLAS OTS–28–1.27–04
– not recommended in Application (see Para 3C)

SL3552

SW1

Fig.3 Test circuit

10n

1n 1n

100

654

ANZAC

TP101

123

L4

RF OUTPUT

L5

10n

10n

1516171819202122232425

L3

1413121110987654

10n

VIDEO

470

18p200

OUTPUT

3

SL3522

PRODUCT DESCRIPTION

The SL3522 is a complete monolithic successive detection
Log/limiting amplifier which can operate over an input
frequency range of 100MHz to 500MHz. Producing a log/lin
characteristic for input signals between -64dBm and +6dBm,
the log amplifier can provide an accuracy of better than
±1.00dB at case temperatures of -55°C and +25°C and an
accuracy of better than ±1.25dB at +125°C. The dynamic
range is better than 75dB over a frequency range of 100MHz
to 400MHz. The graph in fig 4 shows how the dynamic range
is guaranteed over frequency.

The SL3522 consists of 6 Gain stages, 7 Detector stages,
a limiting RF Output buffer and a Video Output amplifier. The
power supply connections to each section are isolated from
each other to aid stability.

The SL3522 consumes 1.1W of power when ALL parts of
the circuit are powered up from a ±5.0V power supply. As the
circuit uses a differential architecture, the power consumption
of the RF gain/detector stages and RF Output Buffer will be
independent of RF input signal level. However, the Video
Output (pin 13) is driven by a single ended emitter follower and
so the power consumption of the Video amplifier will vary with
RF input signal level between pins 27 and 28.(upto 10mA over
2V video output range with max video load of 200Ω //20pF) The
SL3522 has a high RF gain (>50dB) across a wide bandwidth
(>450MHz) when the limiting RF Output Buffer is enabled. The
limiting RF Output Buffer provides a balanced Limited Output
level of nominally –1.0dBm on each RF Output connection (pin
9 and 10), for RF input signal levels on pins 27 and 28 in excess
of –50dBm.

The limiting RF Output Buffer can be isolated from the
other sections of the SL3522, by disconnecting the RF Output
Buffer GND (pin 8) from 0V, and leave the pin floating. This
feature aids stability in applications NOT requiring a Limited RF
Output signal, and lowers the power consumption of the
SL3522 to 0.95Watts, when the other sections are powered up
from a ±5.0V power supply.

Each of the Gain and Detector stages has approximately
12dB of gain, and a significant amount of on-chip RF
decoupling (200pF per stage), also to aid stability. The Video
amplifier provides a positive going output signal proportional to
the log of the amplitude of an RF input applied between pins 27
and 28. The gain and the offset of the Video amplifier can be
adjusted by 3 resistors; R

, RT , and RO which are connected

G

to Gain adjust (pin 19),Trim reference (pin 18) and Offset
adjust (pin 17). With R

set to 1.5kΩ , R

T

can be set to any value

G

between 1kΩ and 2k2Ω and achieve a range in Video Slope of
±20%, centred on 21mV/dB. Similarly, R

can be set to any

O

value between 1kΩ and 2.2KΩ and achieve an offset range of
±0.5V, which should allow the Video Offset to be trimmed to 0V
if required.

The RF input pins (27 and 28) have a 50Ω terminating
resistor connected between them on–chip. These are
capacitively coupled to the I/P gain stage with 20pF on-chip
capacitors. (Refer to APPLICATION NOTES section for
information on how to connect an RF input signal to the device).

100

90

Minimum
guaranteed
dynamic
range (dB)”

80
70
60
50
40
30
20
10

0

100 200 300 400 500 600 700 800

–55°C
+25°C
+125°C

Fig.4 Plot showing guaranteed dynamic range v. frequency

(typical achievable dynamic range lines indicated across temperature)

4

APPLICATION NOTES

SL3522

1) VIDEO–AMPLIFIER

The SL3522 uses a single ended Video amplifier to
produce a trimmable Video transfer characteristic. Both the
gain (Slope) and Offset of the amplifier can be externally
adjusted.

a) Gain and Offset trimming (ref Applications
circuits in figs 5 and 6)

The Gain and Offset control is achieved by adjusting R
and R

respectively. The control is dependent upon their

O

difference from the Trim reference resistor, RT. Adjustment of
Gain has an effect on Offset, but adjustment of Offset does
NOT affect the Gain. Therefore the Gain should be optimised
first. The Offset should only be adjusted once the Gain has
been set.

Fig 7 shows the variation of Video Offset with value of RO,
for a fixed value of R

and RG = 1k5Ω.

T

Fig 8 shows the variation of Video Slope with value of RG,
for a fixed value of R

and RO = 1k5Ω.

T

The Video amplifier incorporates temperature
compensation for Video gain (Slope). To ensure temperature
stability for Video gain (Slope) over the operating temperature
range, it is recommended that the resistors with identical
temperature coefficients of resistance are used for R

and R

T

The Video amplifier does NOT incorporate temperature
compensation for Video Offset. Although it is recommended
that a resistor with identical temperature coefficient of
resistance to R

be used for R

T

, it may be necessary to use an

O

additional external temperature compensating network.

b) Video performance

The Video–amplifier has a critically damped rise time of
16ns (10% - 90%).In order to achieve this transient
performance, it is important to ensure that:-

i) the resistor connected to Trim reference (pin 18), has a
nominal resistance of 1.5kΩ, with a parasitic capacitance
LESS than 5pF.

ii) the load applied to the Video Output (pin 13) does NOT
exceed 200Ω resistance in parallel with 20pF.

Also, the following decoupling should be incorporated:-

i) The Video Output V

(pin 14) should be decoupled with

CC

a 10nF capacitor to the RETURN line from the video load,
connected to Video GND (pin 16), avoiding any common
impedance path.

ii) The Video Output Vee (pin 12) should be decoupled
with a 10nF capacitor DIRECTLY to Video-Output VCC (pin

14).

2) SL3522 AS A LOG AMPLIFIER
with RF output buffer disabled (pin 8 floating)

If the SL3522 is to be used as a Logarithmic successive
detection amplifier only, with no requirement for a limited RF
Output, the RF input (pins 27 and 28) can be driven EITHER
differentially or single ended from a 50Ω source. If being used
with a single ended input, the SIGNAL should be applied to pin
27 and the RETURN should be connected to pin 28, as shown
in the Application circuit diagram in Fig 5.

The SL3522 is VERY stable when used in this way.
Although not a crucial requirement, it is recommended that the
device should be mounted using a ground plane.

3) SL3522 AS A LOG/LIMITING AMPLIFIER

- with RF Output-Buffer ENABLED (pin 8 connected
to GND)

If the SL3522 is to be used as a Limiting or Log/limiting
amplifier with a requirement for a Limited RF Output signal,care
is required in the layout of components and connections around
the device to ensure stability. The following precautions should
be observed (refer to Application circuit diagram in Fig. 6):-

G

.

G

a) The device should be mounted on a ground plane,
ensuring that the impedance between the ground plane and
ALL the GND pins is kept as low as possible. If a multilayer PCB
is used where the ground plane is connected to the GND pins
using through-plated holes (vias), it is essential to ensure that
the vias have a very low impedance. ALL supply decoupling
capacitors should be RF chip capacitors whose leads should be
kept as short as possible.

b) The RF V

connections (pins 3,5,7,11,20,22,24,26)

EE

should be connected to a low impedance copper plane. A two
layer PCB should help to achieve this.

c) The RF input (pins 27 and 28) should be driven with a
balanced source impedance. One way of achieving this is to
use an isolating BALUN transformer (50Ω UNBALANCED →
50Ω BALANCED) connected between the signal source and
the RF input pins. (e.g. Mini circuits TT1–6, TO –75). The device
stability is VERY sensitive to an imbalance of the differential
source impedance at pins 27 and 28. Use of a transmission line
BALUN though, is NOT recommended.

d) The RF Output connections (pins 9 and 10) should each
be loaded with matched impedances ideally 50Ω transmission
lines. The RF Output lines leading away from the device should
be balanced. Driving highly reactive SWR loads is NOT
recommended as these can encourage device instability, as
can an imbalance of the differential load impedance at pins 9
and 10.

e) The RF Output connections (pins 9 and 10) are DC
coupled, and ideally the output pins should be capacitively
coupled to their loads using 1nF capacitors. However the RF
Outputs can drive a DC load to GND and a DC offset of approx.
400mV will exist on each RF Output pin. IT WILL NOT BE
POSSIBLE TO DISABLE THE RF OUTPUT BUFFER UNDER
THESE CONDITIONS.

f) The RF output (pins 9 and 10) has a tendancy to limit on
self noise, particularly at low ambient temperatures (-55°C),
when the RF output buffer is enabled.

NOTE that this will effect the liminting range as the gain of the
RF output buffer will reduce as the amount of noise limiting
increases.

If required the limited RF Output can be attenuated using
an attenuation network as shown in fig. 9. Under these
conditions the effective RF Output currents will be reduced,
allowing the device to operate with a greater margin of
stability.It may be possible to run the device without a BALUN
transformer on the RF input if the total output impedance on the
RF Output >> 50Ω , and the attenuation components are
mounted as close as possible to the RF Output connections
(pins 9 and 10). The RF input connection could then be
configured as in Fig 5.

5

SL3522

–5V V

EE

RF INPUT

RF INPUT

10n

10n

GAIN
ADJUST
R

2k2

G

R

1k5

T

OFFSET
ADJUST
R

2k2

0

262728

SL3522

321

10n

10n

Fig.5 Application circuit successive detection logarithmic function only

10n

10n

GAIN
ADJUST
R

2k2

G

R

1k5

T

OFFSET
ADJUST
R

2k2

0

10n

10n

+5V V

CC

1516171819202122232425

1413121110987654

10n

+5V V

VIDEO

OUTPUT

VIDEO

LOADING

R

200

C 20p

CC

–5V V

EE

262728

1516171819202122232425

SL3522

10n

1413121110987654

10n

VIDEO

OUTPUT

VIDEO

LOADING

R

200

C 20p

321

10n

10n

1n

1n

RF OUTPUT

Fig.6 Application circuit - Log / Limiting function

6