THAT Corporation THAT1440, THAT1430, THAT1420 Datasheet

THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA

Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com

THAT 1420, 1430

Description

The THAT 1420 and 1430 are a new genera

­tion of audio differential line drivers with im­proved performance over conventional
cross-coupled monolithic designs. Both models
exhibit low noise and distortion, high slew rate,
stability under difficult loads, wide output swing,
and have outputs which are short-circuit pro­tected.

In addition both models incorporate patented

OutSmartsÔ technology, a dual feedback-loop de

­sign that prevents the excessive ground currents
typical of cross-coupled output stages (CCOS)
when clipping into single-ended loads

1

.

To overcome this problem, the THAT 1420
and 1430 use two individual negative-feedback
loops to separately control the differential output
voltage and common mode output currents, mak

-

ing the design inherently more stable and less
sensitive to component tolerances than the CCOS.
Most importantly, the dual-feedback design pre­vents the loss of common-mode feedback that
plagues the CCOS designs, avoiding the excessive
ground currents and overly-distorted output
waveform that can result when driving sin­gle-ended loads.

Where minimum output offset voltage with
minimum parts count is desired, the THAT 1430
further improves over existing designs. In con

­ventional CCOS circuits, two relatively high-value
electrolytic capacitors are required to reduce the
offset voltage. By contrast, the THAT 1430 topol

­ogy requires only a resistor and a single film or
ceramic capacitor to achieve the same effect at
lower parts count and price.

THAT Corporation

OutSmartsä Balanced Line Drivers

FEATURES

·

OutSmartsÔ technology tames
clipping behavior into single-ended
loads

·

Pin-compatible with SSM2142

·

Balanced, floating output delivers
transformer-like behavior

·

Stable when driving long cables
and capacitive loads

·

THAT 1430 delivers low output
offset voltage using single capacitor

APPLICATIONS

·

Differential Line Driver

·

Audio Mix Consoles

·

Distribution Amplifiers

·

Audio Equalizers

·

Dynamic Range Processors

·

Digital Effects Processors

·

Telecommunications Systems

·

Instrumentation

·

Hi-Fi Equipment

Din+

Cin+

Cin-

Din-

Out-

Sens+

Out+

Sens-

Vcc

In+

Vee

Gnd

Dout-

Dout+

10k

10k

50

5k

5k

10k

10k

10k

10k

20k

20k

10p

50

THAT 1420

CEXT

CEXT

D

C

AA

&

Figure 1. THAT 1420 Equivalent Circuit Diagram

1. See Gary Hebert’s paper, An Improved Balanced, Floating Output Driver IC, presented at the 108th AES Convention, Feb. 2000

DIP Pin

Number

SO Pin

Number

1420 Pin

Name

1430 Pin

Name

1 3 Out- Out-

2 4 Sens- Cap2

35GndGnd

4 6 In In

5 11 Vee Vee

6 12 Vcc Vcc

7 13 Sens+ Cap1

8 14 Out+ Out+

Table 1. THAT 1420/1430 pin assignments

THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA

Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com

Page 2 THAT1420/1430 Balanced Line Driver

Preliminary Information

Absolute Maximum Ratings (TA= 25°C)

Positive Supply Voltage (Vcc) +18 V Operating Temperature Range (TOP) -40 to +85°C

Negative Supply Voltage (Vee) -18 V Storage Temperature (T

ST

) -40 to +150°C

Output Short Circuit Duration Continuous Junction Temperature (T

J

) 150°C

Power Dissipation (P

D

) TBD mW Lead Temperature (T

LEAD

)(Soldering 60 sec) 300°C

SPECIFICATIONS

2

2. All specifications are subject to change without notice.

3. All measurements taken with V

S

=±18, T=25°C, unless otherwise noted

Electrical Characteristics

3

Parameter Symbol Conditions Min. Typ. Max. Units

Input Impedance Z

IN

45 kW

Gain G1 R

L

=600W

Balanced 4.35 4.65 4.95 dB

Single Ended 4.4 4.6 4.8 dB

Gain G2 R

L

=100kW

Balanced 5.8 6 6.2 dB

Single Ended 5.8 6 6.2 dB

DC Power Supply
Rejection Ratio PSRR ±4V to ±18V 80 105 dB

Output Common-Mode
Rejection Ratio OCMRR f=1kHz, BBC Method 50 68 dB

Output Signal Balance Ratio SBR f=1kHz, BBC Method 28 40 dB

THD+N (Balanced) THD+N

1

20Hz-20kHz 0.001 %

1kHz 0.0005 %

THD+N (Single Ended) THD+N

2

VO=10 V

RMS,RL

=600W, 20Hz-20kHz 0.0018 %

Output Noise SNR Bal. Mode, 20 kHz BW -104 dBV

Headroom HR 0.1% THD+N 25 dBV

Slew Rate SR 16 V/mS

Output Common Mode
Voltage Offset V

OCM

RL=600W, w/o Sense capacitors -300 ±60 300 mV

THAT1420 V

OCM

RL=600W, w/ Sense capacitors -6 ±4 6 mV

Output Common Mode
Voltage Offset V

OCM

RL=600W, w/o Sense capacitor -400 ±80 400 mV

THAT1430 V

OCM

RL=600W, w/ Sense capacitor -20 ±10 20 mV

Theory of Operation

OutSmartsÔ technology

The THAT 1420 and 1430 are similar devices,
both employing the OutSmarts topology, a variation
of circuitry originally developed at Audio Toys, Inc.
OutSmarts topology employs two negative-feedback
loops -- one to control the differential signal, and a
separate loop to control the common mode output
levels.

Figures 2 and 3 show the gain core common to
both the THAT 1420 and 1430. The gain core is a
single amplifier that includes two differential input
pairs, C

in+/-

and D

in+/-

, and complementary outputs,

V

out+

and V

out-,

related to each other by two gain ex

-

pressions, A

D

(s) and AC(s). The first pair of differen

-

tial inputs, D

in+/-

, are connected to the differential
feedback network between the outputs and the input
signal. The second differential input pair, C

in+/-

,is
connected to a bridge circuit which generates an er­ror signal that is used to servo the common-mode be­havior of the outputs. The loop equations are then,

()

DD DADD

OUT OUT OUT D IN IN+- +-

-= = -D

where A

D

is the differential open-loop gain, and

()

DD DACC

OUT OUT OUT C IN IN+- +-

+= = -

å

where ACis the common-mode open-loop gain.

THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA

Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com

Rev. 4/24/01 Page 3
Preliminary Information

Electrical Characteristics (cont’d.)

Parameter Symbol Conditions Min. Typ. Max. Units

Differential Output Offset V

OOD

RL=600W -10 ±4 10 mV

Differential Output
Voltage Swing,Pos V

IN

= ±18V VCC-2 V

Differential Output
Voltage Swing,Neg V

IN

= ±18V VEE+2 V

Output Impedance Z

O

40 50 60 W

Quiescent Supply Current I

S

Unloaded, VIN= 0 4 5.2 mA

Short Circuit Output Current I

SC

60 70 mA

Voltage Supply Range ±4 ±18 V

Din+

Cin+

Cin-

Din-

Out-

Sens+

Out+

Sens-

Vcc

In+

Vee

Gnd

Dout-

Dout+

10k

10k

50

5k

5k

10k

10k

10k

10k

20k

20k

10p

50

THAT 1420

CEXT

CEXT

D

C

AA

&

Figure 2. THAT 1420 Equivalent Circuit Diagram