PBL3772-1 View Datasheet(PDF) - Ericsson

Part Name

Description

Manufacturer

PBL3772-1

Dual Stepper Motor Driver

Ericsson  

PBL 3772/1

Contributing to the low power

dissipation is the fact that the upper

recirculation diodes in the output H-

bridge are connected externally to the

circuit. These diodes shall be of fast

type, with a trr of less than 100 ns.

Common types are UF4001 or BYV27.

A low pass filter in series with the

comparator input prevents erroneous

switching due to switching transients.

The recommended filter component

values, 1 kohm and 820 pF, are suitable

for a wide range of motors and operatio-

nal conditions.

Since the low-pass filtering action

introduces a small delay of the signal to

the comparator, peak voltage across the

sensing resistor, and hence the peak

motor current, will reach a slightly higher

level than than what is defined by the

comparator threshold, VCH , set by the

reference input V (V = 450 mV at V =

R CH

R

2.5 V).

The time constant of the low-pass filter

may therefore be reduced to minimize

the delay and optimize low-current

perform-ance. Increasing the time

constant may result in unstable swit-

ching. The time constant should be

adjusted by changing the CC value.

The frequency of the clock oscillator is

set by the RT-CT timing components at

the RC pin. The recommended values

result in a clock frequency (= switching

frequency) of 26.5 kHz. A lower frequen-

cy will result in higher current ripple, but

may improve low-current level linearity.

A higher clock frequency reduces

current ripple, but increases the

switching losses in the IC and possibly

the iron losses in the motor. If the clock

frequency needs to be changed, the CT

capacitor value should be adjusted. The

recommended RT resistor value is 15

kohm.

The sensing resistor R , should be

S

selected for maximum motor current.

The relationship between peak motor

current, reference voltage and the value

of RS is described under Current control

above. Be sure not to exceed the

maximum output current which is

1200 mA peak when only one channel is

activated. Or recommended output

current, which is 1000 mA peak, when

both channels is activated.

Motor selection

The PBL 3772/1 is designed for two-

phase bipolar stepper motors, i.e.,

motors that have only one winding per

phase.

The chopping principle of the PBL

3772/1 is based on a constant

frequency and a varying duty cycle. This

scheme imposes certain restrictions on

motor selection. Unstable chopping can

occur if the chopping duty cycle exceeds

approximately 50%. See figure 3 for

definitions. To avoid this, it is necessary

to choose a motor with a low winding

resistance and inductance, i.e. windings

with a few turns.

It is not possible to use a motor that is

rated for the same voltage as the actual

supply voltage. Only rated current needs

to be considered. Typical motors to be

used together with the PBL 3772/1 have

VCC (+5V)

To

mP

+2.5V

25

D0

14

V DD

Sign1

16 D7

DA1

PBM 3960/1

27 A0

28 A1

15

1

7

WR

CS

9 RESET

V Ref

V SS

Sign2

DA2

2

0.1 mF

RB

RB

0.5 W

0.5 W

22

18

11

27

5

V CC

V MM1

V BB1

V MM2

V

BB2

MA1

12

19

Phase 1

10

20

VR1

MB1

PBL 3772/1

4

26

Phase 2

6

25

VR2

MA2

MB2

RC GND

23 1, 2,

+5 V 15 kW

3, 9,

28, 13,

3300 pF

14, 15,

16, 17,

C1

E1

21 10

1 kW

C2

24

E2

6

1 kW

820 pF

RS

820 pF

RS

D1

12

8

4

7

D3

0.5 W

0.5 W

V MM

+

10 mF

D2

STEPPER

MOTOR

D4

V MM

D1 - D4 are UF 4001 or

BYV 27, t rr = 100 ns

Pin numbers refer to

PLCC package.

Figure 7. Microstepping system with PBM 3960/1 and PBL 3772/1.

6

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