UNITRODE UC1620, UC2620 Technical data

UC1620

UC1620

UC3620

Switchmode Driver for 3- Brushless DC Motors

FEATURES

∙2A Continuous, 3A Peak Output Current

∙8V to 40V Operation

∙Internal High Gain Amplifier for Velocity Control Applications

∙TTL Compatible Hall Inputs

∙Mask Programmable Decode Logic

∙Pulse-by-Pulse Current Limiting

∙Internal Thermal Shutdown Protection

∙Under-Voltage Lockout

∙Available in SP Hermetic Package

DESCRIPTION

The UC3620 is a brushless DC motor driver capable of decoding and driving all 3 windings of a 3-phase brushless DC motor. In addition, an on-board current comparator, oscillator, and high gain Op-Amp provide all necessary circuitry for implementing a high performance, chopped mode servo amplifier. Full protection, including thermal shutdown, pulse-by-pulse current limiting, and under-voltage lockout aid in the simple implementation of reliable designs. Both conducted and radiated EMI have been greatly reduced by limiting the output dv/dt to 150V/μs for any load condition.

The UC1620SP is characterized for operation over the full military temperature range of -55°C to +125°C, while the UC3620SP is characterized for 0°C to +70°C.

BLOCK DIAGRAM

3/97

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ABSOLUTE MAXIMUM RATINGS (Note 1)

Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40V Output Current, Source or Sink

Non-Repetitive (t = 100μsec), lo . . . . . . . . . . . . . . . . . . . . 3A Repetitive (80% on - 20% off; tON = 10ms) . . . . . . . . . . 2.5A DC Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +Vcc Logic Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +Vcc

Total Power Dissipation (at TCASE = 75° C)

for SP Package (Note 2). . . . . . . . . . . . . . . . . . . . . . . . . . 15W Storage Temperature . . . . . . . . . . . . . . . . . . . . -65°C to +150°C Operating Junction Temperature . . . . . . . . . . . -55°C to +150°C

Note 1: All voltages are with respect to ground. Currents are positive into, negative out of the specified terminal.

Note 2: Consult Packaging Section of Databook for thermal limitations and considerations of package.

UC1620

UC3620

CONNECTION DIAGRAMS

SP Hermetic Power DIL

ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for TA = 0°C to 70°C for 3620; T A = 55°C to +125°C for UC1620; V CC = 20V, RT = 20V, RT = 10k, CT = -2.2nF. TA=TJ.

PARAMETER	TEST CONDITIONS		UC3620			UC1620		UNIT
		MIN	TYP	MAX	MIN	TYP	MAX
Error Amplifier Section
Input Offset Voltage			1.5	10		1.5	10	mV
Input Bias Current			-.25	-2.0		-.25	-2.0	μA
Input Offset Current			15	250		15	250	nA
Common Mode Range	Vcc = 8V to 40V	0		VIN-2	0		VIN-2	V
Open Loop Gain	VCOMP = 1V to 4V	80	100		75	100		dB
Unity Gain Bandwidth	TJ = 25°C, Note 2		0.8			0.8		MHz
Output Sink Current	VCOMP = 1V		2			2		mA
Output Source Current	VCOMP = 4V		8			8		mA
Current Sense Section
Input Bias Current			-2.0	-5		-2.0	-5	μA
Internal Clamp		.425	0.5	.575	.405	0.5	.595	V
Divider Gain		.180	0.2	.220	.170	0.2	.230	V/V
Internal Offset Voltage		.8	1.0	1.2	.75	1.0	1.25	V
Timing Section
Output Off Time		18	20	22	17	20	23	μs
Upper Mono Threshold			5.0			5.0		V
Lower Mono Threshold			2.0			2.0		V
Decoder Section
High-Level Input Voltage		2.2			2.5			V
Low-Level Input Voltage				0.8			0.8	V
High-Level Input Current				10			10	μA
Low-Level Input Current		-10			-10			μA
Output Section
Output Leakage Current	VCC = 40V			500			1500	μA
VF1 Schottky Diode	IO = 2A		1.5	2.0		1.5	2.0	V
VF1 Substrate Diode	IO = 2A		2.2	3.0		2.2	3.0	V
Total Output Voltage Drop	IO = 2A, Note 3		3.0	3.6		3.0	3.6	V

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UC1620

UC3620

ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for TA = 0°C to 70°C for 3620; T A = 55°C to +125°C for UC1620; V CC = 20V, RT = 20V, RT = 10k, CT = -2.2nF. TA=TJ.

PARAMETER	TEST CONDITIONS		UC3620			UC1620		UNIT
		MIN	TYP	MAX	MIN	TYP	MAX
Output Section (cont.)
Output Rise Time	RL = 44Ω		150			150		ns
Output Fall Time	RL = 44Ω		150			150		ns
Under Voltage Lockout
Startup Threshold				8.0			8.0	V
Threshold Hysteresis			0.5			0.5		V
Thermal Shutdown
Junction Temperature	Note 2	150		180	150		180	°C
Total Standby Current
Supply Current			32	55		32	55	mA

Note 2: These parameters, although guaranteed over the recommended operating conditions, are not 100% tested in production. Note 3: The total voltage drop is defined as the sum of both top and bottom side driver.

TABLE 1

STEP	FWD/	Ha	Hb	Hc	AOUT	BOUT	COUT
	REV
1	1	1	0	1	H	L	O
2	1	1	0	0	H	O	L
3	1	1	1	0	O	H	L
4	1	0	1	0	L	H	O
5	1	0	1	1	L	O	H
6	1	0	0	1	O	L	H
1	0	1	0	1	L	H	O
2	0	1	0	0	L	O	H
3	0	1	1	0	O	L	H
4	0	0	1	0	H	L	O
5	0	0	1	1	H	O	L
6	0	0	0	1	O	H	L

H = HIGH OUTPUT

L = LOW OUTPUT

O = OPEN OUTPUT

Hall lines require pull-up resistors.

CURRENT SENSING

Referring to Figure 1, emitter current is sensed across RS and fed back through a low pass filter to the current sense pin 7. This filter is required to eliminate false triggering of the monostable due to leading edge current spikes. Actual filter values, although somewhat dependent on external loads, will generally be in the 1kΩ and 1000pF range.

TIMING

An R-C time constant on pin 9 is used by the monostable to generate a fixed off time at the outputs according to the formula:

TOFF = .916RTCT

As the peak current in the emitters approaches the value at the minus (-) input of the on-board comparator, the monostable is triggered, causing the outputs to be turned

CIRCUIT DESCRIPTION

The UC3620 is designed for implementation of a complete 3- brushless DC servo drive using a minimum number of external components. Below is a functional description of each major circuit feature.

DECODER

Table 1 shows the decoding scheme used in the UC3620

to decode and drive each of three high current totem pole output stages. A forward/reverse signal, pin 13, is used to

provide direction. At any point in time, one driver is sourcing, one driver is sinking, and the remaining driver is off

or tri-stated. Pulse width modulation is accomplished by turning the sink driver off during the monostable reset

time, producing a fixed off-time chop mode. Controlled

output rise and fall times help reduce electrical switching

noise while maintaining relatively small switching losses.

Figure 1. Current Sense Filter

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