UNITRODE UC1637, UC2637, UC3637 Technical data

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Switched Mode Controller for DC Motor Drive

UC1637
UC2637
UC3637

FEATURES

• Single or Dual Supply
Operation

±

•

2.5V to ±20V Input Supply

Range

±

•

5% Initial Oscillator
Accuracy; ± 10% Over
Temperature

• Pulse-by-Pulse Current
Limiting

• Under-Voltage Lockout

• Shutdown Input with

Temperature Compensated

2.5V Threshold

• Uncommitted PWM
Comparators for Design
Flexibility

• Dual 100mA, Source/Sink
Output Drivers

BLOCK DIAGRAM

DESCRIPTION

The UC1637 i s a p ul se width modulator circuit intended to be used for a variety of
PWM motor drive and amplifier applications requiring either uni-directional or bi­directiona l drive circuits. When used to replace conventional drivers, this circuit
can increase efficiency and reduce component costs for many applications. All
necessary circuitr y is included to generate an analog error signal and modulate
two bi-direc tional pulse train outpu ts in propor tion to the error signal magnitude
and polarity.

This monolithic device contains a sawtooth oscillator, error amplifier, and two
PWM compar ators with ±100mA output stages as standard features. Protection
circuitry includes under-voltage lockout, pulse-by-pulse current limiting, and a
shutdown port with a 2.5V temperature compensated threshold.

The UC1637 is characterized for operation over the full military temperature range
of -55°C to +125°C, while the UC2637 and UC3637 are characterized for -25°C to
+85°C and 0°C to +70°C, respectively.

ABSOLUTE MAXIMUM RATINGS (Note 1)

Supply Voltage (±Vs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±20V

Output Current, Source/Sink (Pins 4, 7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500mA

Analog Inputs (Pins 1, 2, 3, 8, 9, 10, 11 12, 13, 14, 15, 16) . . . . . . . . . . . . . . . . . . . . . . . ±Vs

Error Amplifier Output Current (Pin 17) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±20mA

Oscillator Charging Current (Pin 18). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -2mA

Power Dissipation at TA = 25°C (Note 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000mW

Power Dissipation at TC = 25°C (Note 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2000mW

Storage Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65°C to +150°C

Lead Temperature (Soldering, 10 Seconds). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +300°C

Note 1: Currents are positive into, negative out of the specified terminal.
Note 2: Consult Packaging Section of Databook for thermal limitations and considerations

of package.

6/97

CONNECTION DIAGRAM

UC1637
UC2637
UC3637

DIL-18 (TOP VIEW)
J or N Package

SOIC-20 (TOP VIEW)
DW Package

PLCC-20, LCC-20
(TOP VIEW)
Q, L Packages

PACKAGE PIN

FUNCTION

FUNCTION PIN

+V

TH

C

T

-V

TH

A

OUT

-V

S

N/C 6
+V

S

B

OUT

+B

IN

-B

-A
+A

IN
IN

IN

10
11
12

+C/L 13

-C/L 14
SHUTDOWN 15
N/C 16
+E/A 17

-E/A 18
E/A

OUTPUT 19

I

SET

20

1
2
3
4
5

7
8
9

ELECTRICAL CHARACTERISTICS:

Unless otherwise stated, these specifications apply for TA = -55°C to +125°C for the
UC1637; -25°C to +85°C for the UC2637; and 0°C to +70°C for the UC3637; +VS =
+15V, -VS = - 15V, +V

= 5V, -V

TH

= -5V, RT = 16.7kΩ, CT = 1500pF, TA=T

TH

PARAMETER TEST CONDITIONS UC1637/UC2637 UC3637 UNITS

MIN TYP MAX MIN TYP MAX

Oscillator

Initial Accuracy TJ = 25°C (Note 6) 9.4 10 10.6 9 10 11 kHz
Voltage Stability V

= ±5V to ±20V, V

S

V

= -3V

PIN 3

PIN 1

= 3V,

57 57%

Temperature Stability Over Operating Range (Note 3) 0.5 2 0.5 2 %
+V

Input Bias Current V

TH

Input Bias Current V

-V

TH

+V

-V

TH,

Input Range +VS-2 -VS+2 +VS-2 -VS+2 V

TH

= 6V -10 0.1 10 -10 0.1 10

PIN 2

= 0V -10 -0.5 -10 -0.5

PIN 2

Error Amplifier

Input Offset Voltage VCM = 0V 1.5 5 1.5 10 mV
Input Bias Current V
Input Offset Current V
Common Mode Range V
Open Loop Voltage G ai n R

= 0V 0.5 5 0.5 5

CM

= 0V 0.1 1 0.1 1

CM

= ±2.5 to 20V -VS+2 +VS-VS+2 +V

S

= 10k 75 100 80 100 dB

L

S

Slew Rate 15 15 V/
Unity Gain Bandwidth 2 2 MHz
CMRR Over Common Mode Ra ng e 75 100 75 100 dB
PSRR VS = ±2.5 to ±20V 75 110 75 110 dB

J.

A

µ

A

µ

A

µ

A

µ

V

µ

S

2

UC1637
UC2637
UC3637

ELECTRICAL CHARACTERISTICS:

PARAMETERS TEST CONDITIONS UC1637/UC2637 UC3637 UNITS

Error Amplifier (Continued)

Output Sink Current V
Output Source Current V
High Level Output Voltage 13 13.6 13 13.6 V
Low Level Output Voltage -14.8 -13 -14.8 -13 V

PWM Comparators

Input Offset Voltage V
Input Bias Current V
Input Hysteresis V
Common Mode range V

Current Limit

Input Offset Voltage V
Input Offset Voltage T.C. -0.2 -0.2 mV/°C
Input Bias Current -10 -1.5 -10 -1.5
Common Mode Range V

Shutdown

Shutdown Threshold (Note 4) -2.3 -2.5 -2.7 -2.3 -2.5 -2.7 V
Hysteresis 40 40 mV
Input Bias Current V

Under-Voltage Lockout

Start Threshold (Note 5) 4.15 5.0 4.15 5.0 V
Hysteresis 0.25 0.25 mV

Total Standby Current

Supply Current 8.5 15 8.5 15 mA

Output Section

Output Low Level I

Output High Level I

Rise Time (Note 3) C
Fall Time (Note 3) C

Note 3: These parameters, although guaranteed over the recommended operating conditions, are not 100% tested in production.
Note 4: Parameter measured with respect to +VS (Pin 6).
Note 5: Parameter meas ure d at +V
Note 6: R

and CT referenced to Ground.

T

PIN 17
PIN 17

= 0V 20 20 mV

CM

= 0V 2 10 2 10

CM

= 0V 10 10 mV

CM

= ±5V to ±20V -VS+1 +VS-2 -VS+1 +VS-2 V

S

= 0V, TJ = 25°C 190 200 210 180 200 220 mV

CM

= ±2.5V to ±20V -V

S

PIN 14

= 20mA -14.9 -13 -14.9 -13 V

SINK

= 100mA -14.5 -13 -14.5 -13

I

SINK
SOURCE

I

SOURCE

(Pin 6) with respect to -VS (Pin 5).

S

Unless otherwise stated, these specifications apply for TA = -55°C to +125°C for the
UC1637; -25°C to +85°C for the UC2637; and 0°C to +70°C for the UC3637: VS =
+15V, -VS = - 15V, +V

= 5V, -VTH = -5V, RT = 16.7kΩ, CT = 1500pF, TA=T

TH

J.

MIN TYP MAX MIN TYP MAX

= 0V -50 -20 -50 -20 mA
= 0V 5 11 5 11 mA

µ

µ

= +VS to -V

S

S

-10 -0.5 -10 -0.5

+VS-3 -V

S

+VS-3 V

µ

= 20mA 13 13.5 13 13.5 V

= 100mA 12 13.5 12 13.5

= Inf, TJ = 25°C 100 600 100 600 ns

L

= Inf, TJ = 25°C 100 300 100 300 ns

L

A

A

A

FUNCTIONAL DESCRIPTION

Following is a descr iption of each of the functional blocks
shown in the Block Diagram.

Oscillator

The oscillator consists of two comparators, a charging
and dischar ging current source, a current sourc e set ter­minal, l
of the oscilla tor waveform is set externally by applying a
voltage at pins +V

and a flip- flop. The upper and lower threshold

SET

and -VTH respectively. The +VTH ter-

TH

minal voltage is buffered internally and also applied to the

terminal to develop the capacitor charging current

l

SET

through R

. If RT is referenced to -VS as shown in Figure

T

1, both the threshold voltage and charging current will
vary proportionally to the supply differential, and the oscil­lator frequency will remain constant. The triangle wave­form oscillators frequency and voltage amplitude is
determ ined by the external components using the formulas
given in Figure 1.

3