LV8728MR D

LV8728MR
Stepper Motor Driver,
PWM, Constant-Current Control,
1/128 step
Overview
The LV8728MR is a PWM current-controlled micro step stepper motor
driver. This driver can perform eight types of excitation mode from Full step
to 1/128 step and can drive simply by the CLK input.
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Function
 Single-channel PWM current control stepper motor driver
 BiCDMOS process IC
 Output on-resistance (upper side: 0.3 ; lower side: 0.25 ; total of upper
and lower: 0.55 ; Ta = 25C, IO = 2.0A)
 Full, Half, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128 step excitation mode are
selectable
 Advance the excitation step with the only step signal input
 Available forward reverse control
 IO max = 2.0A
 Over-current protection circuit
 Thermal shutdown circuit
 Input pull down resistance
 With reset pin and enable pin.
MFP30KR (375mil)
ORDERING INFORMATION
Ordering Code:
LV8728MR-AH
Package
MFP30KR
(Pb-Free / Halogen Free)
Shipping (quantity/packing)
1000 / Tape & Reel
Typical Applications
 Printer (Multi-function printer, 3D printer, etc.)
 Security camera
 Scanner
 Stage light
† For information on tape and reel specifications, including part
orientation and tape sizes, please refer to our Tape and Reel
Packaging Specifications Brochure, BRD8011/D.
http://www.onsemi.com/pub_link/Collateral/BRD8011-D.PDF
Maximum Ratings (Note 1)
Parameter
Symbol
Conditions
Ratings
Unit
Maximum supply voltage
VM max
VM , VM1 , VM2
36
Maximum output current
IO max
Per 1ch
2.0
V
A
Maximum logic input voltage
VIN max
ST , MD1 , MD2 , MD3 , OE , RST , FR ,
STEP
6
V
Maximum FDT input voltage
VFDT max
6
V
Maximum VREF input voltage
VREF max
6
V
Maximum MO input voltage
VMO max
6
V
Maximum DOWN input voltage
VDOWN max
6
V
Allowable power dissipation (Note 2)
Pd max
1.55
W
Operating temperature
Topr
-30 to +85
C
Storage temperature
Tstg
-55 to +150
C
1. Stresses exceeding those listed in the Absolute Maximum Rating table may damage the device. If any of these limits are exceeded,
device functionality should not be assumed, damage may occur and reliability may be affected.
2. Specified circuit board: 76.1mm114.3mm1.6mm, glass epoxy board.
© Semiconductor Components Industries, LLC, 2016
June 2016 - Rev. 1
1
Publication Order Number:
LV8728MR/D
LV8728MR
Recommended Operating Ranges (Note 3)
Parameter
Symbol
Conditions
Ratings
Supply voltage range
VM
VM , VM1 , VM2
Logic input voltage
VIN
ST , MD1 , MD2 , MD3 , OE , RST , FR , STEP
FDT input voltage range
VREF input voltage range
Unit
9 to 32
V
0 to 5
V
VFDT
0 to 5
V
VREF
0 to 3
V
3. Functional operation above the stresses listed in the Recommended Operating Ranges is not implied. Extended exposure to stresses
beyond the Recommended Operating Ranges limits may affect device reliability.
Electrical Characteristics at Ta=25°C, VM=24V, VREF=1.5V unless otherwise noted. (Note 4)
Parameter
Symbol
Conditions
Ratings
min
typ
max
Unit
Standby mode current drain
IMst
ST = “L” , VM+VM1+VM2
70
100
A
Current drain
IM
3.3
4.6
mA
Thermal shutdown
temperature
Thermal hysteresis width
TSD
ST = “H”, OE = “H”, no load
VM+VM1+VM2
Guaranteed by design
180
200
C
TSD
Guaranteed by design
Logic pin input current
IINL
ST , MD1 , MD2 , MD3 , OE , RST ,
FR , STEP , VIN = 0.8V
ST , MD1 , MD2 , MD3 , OE , RST ,
FR , STEP , VIN = 5V
IINH
Logic input
voltage
High
VINH
ST , MD1 , MD2 , MD3 , OE , RST ,
Low
VINL
FR , STEP
150
3
8
15
A
30
50
70
A
2.0
5.0
V
0
0.8
V
FDT pin high level voltage
Vfdth
3.5
FDT pin middle level voltage
Vfdtm
1.1
FDT pin low level voltage
Vfdtl
V
3.1
V
0.8
V
Chopping frequency
Fch
OSC1 pin charge/discharge
current
Chopping oscillation circuit
threshold voltage
Iosc1
Vtup1
0.8
1
1.2
V
Vtdown1
0.3
0.5
0.7
V
VREF pin input voltage
Iref
DOWN output residual voltage
VOlDOWN
Idown = 1mA
40
100
mV
MO pin residual voltage
VOlMO
Imo = 1mA
40
100
mV
Hold current switching
frequency
OSC2 pin charge/discharge
current
Hold current switching
frequency threshold voltage
Fdown
Cosc2 = 1500pF
1.12
1.6
2.08
Hz
Iosc2
7
10
13
A
Vtup2
0.8
1
1.2
V
Vtdown2
0.3
0.5
0.7
V
VREG1 output voltage
Vreg1
4.7
5
5.3
V
VREG2 output voltage
Vreg2
18
19
20
V
Output on-resistance
Ronu
IO = 2.0A, upper side ON resistance
0.3
0.42
Ω
Rond
IO = 2.0A, lower side ON resistance
0.25
0.35
Ω
IOleak
VD
VM = 36V
50
A
ID = -2.0A
VRF
VREF = 1.5V, Current ratio 100%
Output leakage current
Diode forward voltage
Current setting reference
voltage
Cosc1 = 100pF
C
40
VREF = 1.5V
70
100
130
kHz
7
10
13
A
A
-0.5
0.285
1.1
1.4
V
0.3
0.315
V
4. Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted.
Product performance may not be indicated by the Electrical Characteristics if operated under different conditions.
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2
LV8728MR
Package Dimensions
unit : mm
SOIC30 W / MFP30KR (375 mil)
CASE 751CH
ISSUE A
15.55 MAX
15.2
0~10
0.1
0.2
0.65
0.3
10.5
(4.4)
(5.1)
0.1
LASER MARKED
INDEX
7.9
30
1 2
+0.15
0.35 −0.05
1.0
0.25
0.15
S
0.1
0.10 S
0.1 (2.25)
2.45 MAX
(0.6)
1.15
SOLDERING FOOTPRINT*
9.75
(Unit: mm)
1.00
0.50
NOTE: The measurements are not to guarantee but for reference only.
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3
+0.15
−0.05
LV8728MR
Pin Assignment
1
VREG2
VREG1 30
2
VM
3
OUT1A
MD1 28
4
PGND1
MD2 27
5
VM1
MD3 26
6
RF1
OE 25
7
OUT1B
RST 24
8
NC
GND 23
9
OUT2A
ST 29
FR 22
10 RF2
STEP 21
11 VM2
OSC1 20
12 PGND2
OSC2 19
13 OUT2B
FDT 18
14 GND
DOWN 17
15 VREF
MO 16
Pd max – Ta
Allowable power dissipation, Pdmax - W
1.8
Mounted on a board (76.1mm×114.3mm×1.6, Glass epoxy)
1.6
1.55
1.4
1.2
1
Independent IC
0.8
0.806
0.8
0.6
0.416
0.4
0.2
0
-20
0
20
40
60
Ambient temperature, Ta - C
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4
80
100
LV8728MR
RF2
OUT2B
OUT2A
VM2
VM1
OUT1B
OUT1A
RF1
VREG2
Block Diagram
VM
Output preamplifier
stage
PGND2
Output preamplifier
stage
PGND1
Output preamplifier
stage
Output preamplifier
stage
Regulator 2
MO
VREG1
Regulator 1
Output control logic
VREF
Current select
circuit
Current select
circuit
Oscillator
circuit
Decay Mode
setting circuit
TSD
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5
OSC1
FDT
OE
RST
FR
STEP
MD3
MD2
MD1
OSC2
UVLO
ST
GND
DOWN
LV8728MR
Pin Functions
Pin No.
Pin Name
Pin Function
21
22
24
25
26
27
28
STEP
FR
RST
OE
MD3
MD2
MD1
Step clock pulse signal input pin
Forward / Reverse signal input pin
Reset signal input pin
Output enable signal input pin
Excitation mode switching pin
Excitation mode switching pin
Excitation mode switching pin
29
ST
Chip enable pin
3
4
5
6
OUT1A
PGND1
VM1
RF1
7
9
10
OUT1B
OUT2A
RF2
11
12
13
VM2
PGND2
OUT2B
Channel 1 output A pin
Channel 1 Power ground pin
Channel 1 motor power supply pin
Channel 1 current sense resistor
pin
Channel 1 output B pin
Channel 2 output A pin
Channel 2 current sense resistor
pin
Channel 2 motor power supply pin
Channel 2 Power ground pin
Channel 2 output B pin
15
VREF
Equivalent Circuit
Constant-current control reference
voltage input pin.
Continued on next page
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6
LV8728MR
Continued from preceding page
Pin No.
Pin Name
Pin Function
Equivalent Circuit
1
VREG2
Internal regulator capacitor
connection pin.
30
VREG1
Internal regulator capacitor
connection pin.
16
17
MO
DOWN
Output pin for position detecting
Output pin for holding current
reduction
19
OSC2
Capacitor connection pin for STEP
signal off detection time setting
When not using the current
reduction by DOWN pin, need to
connect OSC2 pin to GND at 10kΩ
(recommended value).
20
OSC1
Capacitor connection pin for
chopping frequency setting.
14
23
GND
GND
Ground pin
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LV8728MR
Functional Description
3. STEP pin function
1. Input Pin Function
Each input terminal has the function to prevent the
flow of the current from an input to a power supply.
Therefore, Even if a power supply (VM) is turned off
in the state that applied voltage to an input terminal,
the electric current does not flow into the power
supply.
Input
Operating mode
ST
STEP
Low
Don’t care
Standby mode
High
Excitation step is proceeded
High
Excitation step is kept
2. Stand-by function
When ST pin is at low levels, the IC enters stand-by
mode, all logic is reset and output is turned OFF.
When ST pin is at high levels, the stand-by mode is
released.
4. Input Timing
Tsteph/Tstepl: Clock H/L pulse width (min 500ns)
Tds: Data set-up time (min 500ns)
Tdh: Data hold time (min 500ns)
5. Position detection monitor function
The MO position detection monitoring pin is an
open drain type.
When the excitation position is in the initial position,
the MO output is placed in the ON state.
(Refer to "Examples of current waveforms in each
of the excitation modes.")
MO
Status
ON
Initial position
OFF
Except initial position
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8
LV8728MR
6. Excitation mode setting function
Set the excitation setting as shown in the following
Input
table by setting MD1 pin, MD2 pin and MD3 pin.
Excitation
Initial position
MD3
MD2
MD1
mode
1ch current
2ch current
Low
Low
Low
Full step
100%
-100%
Low
Low
High
Half step
100%
0%
0%
Low
High
Low
1/4 step
100%
Low
High
High
1/8 step
100%
0%
High
Low
Low
1/16 step
100%
0%
0%
High
Low
High
1/32 step
100%
High
High
Low
1/64 step
100%
0%
High
High
High
1/128 step
100%
0%
The initial position is also the default state at start-up
and excitation position at counter-reset in each
excitation mode.
7. Output enable function
When the OE pin is set Low, the output is forced OFF
and goes to high impedance. However, the internal
logic circuits are operating, so the excitation position
proceeds when the STEP is input. Therefore, when
OE pin is returned to High, the output level conforms
to the excitation position that is advanced by the
STEP input.
OE
Operating mode
Low
Output OFF
High
Output ON
8. Reset function
When the RST pin is set Low, the excitation position
of the output is set to the initial position forcibly and
MO pin output is turn ON state. And then by setting
RST pin is High, the excitation position moves
forward with the next step signal.
RST
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9
Operating mode
Low
Reset status
High
Normal operation
LV8728MR
12. Chopping frequency setting
For constant-current control, LV8728 performs PWM
operation at the chopping frequency determined by the
capacitor (COSC1) connected between the OSC1 pin
and GND.
The calculation for the value of chopping frequency is:
9. Forward / Reverse switching
The internal D/A converter proceeds by a bit on the
rising edge of the step signal input to the STP pin. In
addition, CW and CCW mode are switched by FR pin
setting.
In CW mode, the channel 2 current phase is delayed by
90° relative to the channel 1 current.
In CCW mode, the channel 2 current phase is advanced
by 90° relative to the channel 1 current.
FR
1
1
Where,
Fch
: Chopping frequency [Hz]
IOSC1 : Charge/ Discharge current of OSC1pin [A].
IOSC1 is 10uA (typ) by electrical Characteristics.
COSC1 : Capacitor for chopping frequency setting [F]
Operating mode
Low
Clockwise (CW)
High
Counter-clockwise(CCW)
CW mode
FR
CCW mode
CW mode
For example, when COSC1=100pF and IOSC1=10uA
(typ), the chopping frequency is shown below:
STEP
Excitation
Position
(1)
(2)
(3)
(4)
(5)
(6)
(5)
(4) (3)
(4) (5)
10
100
1ch output
10. Decay mode setting
Current Decay method is selectable as shown below by
applied voltage to the FDT pin.
Decay mode
SLOW Decay
MIXED Decay
0V to 0.8V
FAST Decay
13. Blanking time
If, when exercising PWM constant-current chopping
control over the motor current, the mode is switched
from decay to charge, the recovery current of the
parasitic diode may flow to the current sensing
resistance, causing noise to be carried on the current
sensing resistance pin, and this may result in erroneous
detection. To prevent this erroneous detection, a
blanking period is provided to prevent the noise
occurring during mode switching from being received.
During the blanking time, even if noise is generated in
sense resistor, a mode does not switch from CHARGE
to DECAY. In this IC, the blanking time is fixed to
approximately 1s.
11. Output current setting
Output current is set as shown below by the VREF pin
(applied voltage) and a resistance value between RF1
(2) pin and GND.
5∙
The setting current value above is a 100% output
current in each excitation mode.
Where,
IOUT : Coil current [A]
RRFx : Resistor between RF1 (2) and GND [Ω]
VREF : Input voltage at the VREF pin [V]
For example, when VREF = 1.1V and RF1 (2)
resistance is 0.22Ω, the setting current is shown below:
5
1.1
0.22
100
The higher the chopping frequency is, the greater the
output switching loss becomes. As a result, heat
generation issue arises. The lower the chopping
frequency is, the lesser the heat generation becomes.
However, current ripple occurs. Since noise increases
when switching of chopping takes place, you need to
adjust frequency with the influence to the other devices
into consideration.
2ch output
FDT voltage
3.5V to 5.0V
1.1V to 3.1V or Open
10
10
1.0
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10
LV8728MR
14. DOWN output pin for holding current reduction
The DOWN output pin is an open drain type. When
DOWN pin is turned ON, the motor is holding current.
DOWN
Status
ON
Holding current
OFF
Normal operation
For example, when V1=5V, R1=68kΩ, R2=30kΩ,
R3=5kΩ, RRF1 (2) =0.22Ω, the VREF voltage is shown
below:
RRF1 (2) is Resistor between RF1 (2) and GND [Ω]
VREF is input voltage at the VREF pin [V]
When the DOWN is turned OFF
5 30
1.53
68 30
To avoid to applying high current to a motor coil for
long term at one position, the DOWN output may be
used to reduce the reference current. The DOWN is
asserted when the step clock interval is longer than
TDOWN (STEP signal off detection time). With the
circuit is shown in below. VREF voltage can be reduced
when the DOWN is turned ON. The open-drain output
in once turned ON, is turned OFF at the next rising edge
of STP.
5
1.53
0.22
1.39
When the DOWN is turned ON, combined resistor of
R2 and R3 is about 4.3kΩ.
5 4.3
0.3
68 4.3
0.3
5 0.22
0.27
15. SETP signal off detection time setting
STEP signal off time is determined by the capacitor
(COSC2) connected between the OSC2 pin and GND.
When this function is unused, connect OSC2 pin to
GND at 10kohm (recommendation).
The calculation for the value of STEP signal off
detection time is:
2
0.4
10
Where,
TDOWN : STEP signal off detection time [Sec]
COSC2 : Capacitor for STEP signal off time [F]
For example, when COSC2=1500pF, the STEP signal
off detection time is shown below:
1500
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11
10
0.6
0.4
10
LV8728MR
16. Output current vector locus (one step is normalized to 90 degrees)
(Full step)
Current setting ratio in each excitation mode
STEP
θ0
θ1
θ2
θ3
θ4
θ5
θ6
θ7
θ8
θ9
θ10
θ11
θ12
θ13
θ14
θ15
θ16
θ17
θ18
θ19
θ20
θ21
θ22
θ23
θ24
θ25
1/128 step (%)
1ch
2ch
100
0
100
1
100
2
100
4
100
5
100
6
100
7
100
9
100
10
99
11
99
12
99
13
99
15
99
16
99
17
98
18
98
20
98
21
98
22
97
23
97
24
97
25
96
27
96
28
96
29
95
30
1/64 step (%)
1ch
2ch
100
0
100
2
100
5
100
7
100
10
99
12
99
15
99
17
98
20
98
22
97
24
96
27
96
29
1/32 step (%)
1ch
2ch
100
0
100
5
100
10
99
15
98
20
97
24
96
29
1/16 step (%)
1ch
2ch
100
0
100
10
98
20
96
29
1/8 step (%)
1ch
2ch
100
0
98
1/4 step (%)
1ch
2ch
100
0
Half step (%)
1ch
2ch
100
0
Full step (%)
1ch
2ch
20
Continued on next page
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LV8728MR
Continued from preceding page
STEP
θ26
θ27
θ28
θ29
θ30
θ31
θ32
θ33
θ34
θ35
θ36
θ37
θ38
θ39
θ40
θ41
θ42
θ43
θ44
θ45
θ46
θ47
θ48
θ49
θ50
θ51
θ52
θ53
θ54
θ55
θ56
θ57
θ58
θ59
θ60
θ61
θ62
θ63
θ64
θ65
θ66
θ67
θ68
θ69
θ70
θ71
θ72
θ73
θ74
θ75
θ76
θ77
θ78
θ79
θ80
θ81
θ82
θ83
θ84
θ85
θ86
θ87
θ88
θ89
θ90
1/128 step
1ch
2ch
95
31
95
33
94
34
94
35
93
36
93
37
92
38
92
39
91
41
91
42
90
43
90
44
89
45
89
46
88
47
88
48
87
49
86
50
86
51
85
52
84
53
84
55
83
56
82
57
82
58
81
59
80
60
80
61
79
62
78
62
77
63
77
64
76
65
75
66
74
67
73
68
72
69
72
70
71
71
70
72
69
72
68
73
67
74
66
75
65
76
64
77
63
77
62
78
62
79
61
80
60
80
59
81
58
82
57
82
56
83
55
84
53
84
52
85
51
86
50
86
49
87
48
88
47
88
46
89
45
89
1/64 step (%)
1ch
2ch
95
31
94
34
93
36
92
38
91
41
90
43
89
45
88
47
87
49
86
51
84
53
83
56
82
58
80
60
79
62
77
63
76
65
74
67
72
69
71
71
69
72
67
74
65
76
63
77
62
79
60
80
58
82
56
83
53
84
51
86
49
87
47
88
45
89
1/32 step (%)
1ch
2ch
94
34
92
38
90
43
88
47
86
51
83
56
80
60
77
63
74
67
71
71
67
74
63
77
60
80
56
83
51
86
47
88
1/16 step (%)
1ch
2ch
92
38
88
47
83
56
77
63
71
71
63
77
56
83
47
88
1/8 step (%)
1ch
2ch
92
38
83
56
71
71
56
83
1/4 step (%)
1ch
2ch
92
38
71
71
Half step (%)
1ch
2ch
71
71
Full step (%)
1ch
2ch
100
100
Continued on next page
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LV8728MR
Continued from preceding page
STEP
θ91
θ92
θ93
θ94
θ95
θ96
θ97
θ98
θ99
θ100
θ101
θ102
θ103
θ104
θ105
θ106
θ107
θ108
θ109
θ110
θ111
θ112
θ113
θ114
θ115
θ116
θ117
θ118
θ119
θ120
θ121
θ122
θ123
θ124
θ125
θ126
θ127
θ128
1/128 step
1ch
2ch
44
90
43
90
42
91
41
91
39
92
38
92
37
93
36
93
35
94
34
94
33
95
31
95
30
95
29
96
28
96
27
96
25
97
24
97
23
97
22
98
21
98
20
98
18
98
17
99
16
99
15
99
13
99
12
99
11
99
10
100
9
100
7
100
6
100
5
100
4
100
2
100
1
100
0
100
1/64 step (%)
1ch
2ch
43
90
41
91
38
92
36
93
34
94
31
95
29
96
27
96
24
97
22
98
20
98
17
99
15
99
12
99
10
100
7
100
5
100
2
100
0
100
1/32 step (%)
1ch
2ch
43
90
38
92
34
94
29
96
24
97
20
98
15
99
10
100
5
100
0
100
1/16 step (%)
1ch
2ch
38
92
29
96
20
98
10
100
0
100
1/8 step (%)
1ch
2ch
38
92
20
98
0
100
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1/4 step (%)
1ch
2ch
38
92
0
100
Half step (%)
1ch
2ch
0
100
Full step (%)
1ch
2ch
LV8728MR
17. Current wave example in each excitation mode (Full, Half, 1/16, 1/128 step)
Full step (CW mode)
STEP
MO
(%)
100
I1
0
-100
(%)
100
I2
0
-100
Half step (CW mode)
STEP
MO
(%)
100
I1
0
-100
(%)
100
I2
0
-100
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LV8728MR
1/16 step (CW mode)
STEP
MO
[%]
100
50
I1
0
-50
-100
[%]
100
50
I2
0
-50
-100
1/128 step (CW mode)
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LV8728MR
18. Current control operation
FAST Decay current control: When FDT pin voltage
is 0.8V or less, the constant- current control is
operated in FAST Decay mode.
(Sine-wave increasing direction)
STEP
Setting current
Setting current
Coil current
Blanking Tim e
(Forced CHARGE)
Fch
Current mode
Chopping period
CHARGE
FAST
CHARGE
FAST
(Sine-wave decreasing direction)
STEP
S e ttin g c u rre n t
C o il c u rre n t
B la n k in g T im e
(F o rc e d C H A R G E )
S e ttin g c u rre n t
C h o p p in g p e rio d
Fch
C u rre n t m o d e
CHARGE
FA S T
B la n k in g T im e
The current control of FAST Decay operates with the
follow sequence.
 The IC enters CHARGE mode at a rising edge of the
chopping oscillation. The CHARGE of the blanking
time is forced regardless of the magnitude of the coil
current (ICOIL) and set current (IREF). The
blanking time is approximately 1μs.
 After the period of the blanking time, The IC
operates in CHARGE mode until ICOIL ≥ IREF.
After that, the mode switches to the FAST Decay
FA S T
CHARGE
FA S T
mode and the coil current is attenuated until the end
of a chopping period.
 If ICOIL > IREF state exists when the end of
blanking time, the coil current is attenuated by the
FAST Decay mode until the end of a chopping
period.
Since the attenuation of the current is fast, it is early
that the coil current follows the set current. However,
the current ripple value may be higher.
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LV8728MR
MIXED Decay current control: When FDT pin
voltage is between 1.1V and 3.1V or Open, the
constant- current control is operated in MIXED Decay
mode.
(Sine-wave increasing direction)
STEP
Setting current
Setting current
Coil current
Blanking time
(Forced CHARGE)
Fch
Current mode
CHARGE
SLOW
FAST
CHARGE
SLOW
FAST
(Sine-wave decreasing direction)
STEP
Setting current
Coil current
Blanking time
(Forced CHARGE)
Setting current
Fch
Current mode CHARGE
SLOW
FAST
Forced CHARGE
The current control of MIXED Decay operates with
the follow sequence.
 The IC enters CHARGE mode at a rising edge of the
chopping oscillation. The CHARGE of the blanking
time is forced regardless of the magnitude of the coil
current (ICOIL) and set current (IREF). The
blanking time is approximately 1μs.
 In a period of Blanking Time, the coil current
(ICOIL) and the setting current (IREF) are
compared.
If an ICOIL < IREF state exists during the charge
period:
The IC operates in CHARGE mode until ICOIL ≥
IREF. After that, it switches to SLOW DECAY
mode and then switches to FAST DECAY mode in
the last approximately 1μs of the period.
FAST
CHARGE
SLOW
If no ICOIL < IREF state exists during the charge
period:
The IC switches to FAST DECAY mode and the coil
current is attenuated with the FAST DECAY
operation until the end of a chopping period.
The above operation is repeated. Normally, the IC
operates in SLOW (+ FAST) Decay mode at the sine
wave increasing direction, and the IC operates in
FAST Decay mode at the sine wave decreasing
direction until the current is attenuated. And then the
IC operates in SLOW Decay mode when the current
reaches the set value.
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LV8728MR
SLOW Decay current control: When FDT pin voltage
is 3.5V or more, the constant- current control is
operated in SLOW Decay mode.
(Sine-wave increasing direction)
STEP
Setting current
Setting current
Coil current
Blanking Time
(Forced CHARGE)
Fch
Chopping period
CHARGE
Current mode
CHARGE
SLOW
SLOW
(Sine-wave decreasing direction)
STEP
Setting current
Coil current
Blanking Time
Forced CHARGE)
Setting current
Chopping period
Fch
Current mode
CHARGE
SLOW
Blanking Time
SLOW
Blanking Time
SLOW
 If ICOIL > IREF state exists when the end of
blanking time, the coil current is attenuated by the
SLOW Decay mode until the end of a chopping
period.
The current control of SLOW Decay operates with the
follow sequence.
 The IC enters CHARGE mode at a rising edge of the
chopping oscillation. The CHARGE of the blanking
time is forced regardless of the magnitude of the coil
current (ICOIL) and set current (IREF). The
blanking time is approximately 1μs.
 After the period of the blanking time, The IC
operates in CHARGE mode until ICOIL ≥ IREF.
After that, the mode switches to the SLOW Decay
mode and the coil current is attenuated until the end
of a chopping period.
Since the attenuation of the current is slow, it may be
slow that the coil current follows the set current. Or the
coil current may not follow a set current.
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LV8728MR
19. Over-current protection function
This IC incorporates an over current protection circuit
that, when the output has been shorted by an event such
as shorting to power, shorting to ground and shorting to
other output. And it switches the output to the standby
mode in order to prevent the IC from being damaged.
Three over-current detection modes are shown in the
next page.
When the over current is detected, the over current
protection circuit operates. If the short status continues
for the period of internal timer (≈2μs), the output of
1ch/ 2ch is turned off. If the short status exceeds the
timer latch time (≈256us) set in the internal timer, the
output is turned on again and detects short status again.
If short is detected again, all the outputs of 1ch/ 2ch are
switched to standby mode and the status is kept. To
cancel the standby status, set ST=”L”.
H-bridge
Output state
Output ON
Fault
Detection
Release
Output ON
Output OFF
Timer latch period
(typ:256µs)
2µs
Over-current
Detected
Output OFF 2µs
Over-current
Detected
Internal
counter
1st counter 1st counter 1st counter 1st counter
start
stop
start
stop
2nd counter
start
2nd counter
stop
protection of the final product because it operates
when the temperature exceed the junction temperature
of Tjmax=150°C.
TSD = 180°C (typ)
ΔTSD = 40°C (typ)
20. Thermal shutdown function
The thermal shutdown circuit is incorporated and the
output is turned Off when junction temperature Tj
exceeds 180°C. As the temperature falls by hysteresis,
the output turned on again (automatic restoration).
The thermal shutdown circuit does not guarantee the
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LV8728MR
21. Over current detection mode
Short to Power
VM
VM
Tr1
Tr3
ON
OUTA
M
Tr2
OFF
RF
OFF
OUTB
Tr1
OFF
OUTA
Tr4
Tr2
ON
ON
Tr3
1. High current flows if OUTB short to VM
and Tr4 are ON.
2. If RF voltage> setting voltage, then the
mode switches to SLOW decay.
3. If the voltage between Drain and
Source of Tr4 exceeds the reference
voltage for 2μs, short status is detected.
OFF
OUTB
M
Tr4
ON
RF
Short-circuit
Detection
(left schematic)
1. High current flows if OUTA short to
GND and Tr1 are ON
2. If the voltage between Drain and
Source of Tr1 exceeds the reference
voltage for 2μs, short status is detected.
Short to GND
(right schematic)
1. Without going through RF resistor,
current control does not operate and
current will continue to increase in
CHARGE mode.
2. If the voltage between Drain and
Source of Tr1 exceeds the reference
voltage for 2μs, short status is detected.
1. Without L load, high current flows.
2. If RF voltage> setting voltage, then the
mode switches to SLOW decay.
3. During load short stay in SLOW decay
mode, current does not flow and over
current state is not detected. Then the
mode is switched to FAST decay
according to chopping cycle.
4. Since FAST state is short (≈1μs),
switches to CHARGE mode before short
is detected.
5. If voltage between Drain and Source
exceeds the reference voltage
continuously during blanking time at the
start of CHARGE mode (Tr1), CHARGE
state is fixed (even if RF voltage
exceeds the setting voltage, the mode is
not switched to SLOW decay). After 2us
or so, short is detected.
Load short
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LV8728MR
Application Circuit Example
Calculation for each constant setting according to the
above circuit diagram is as follows.
For example, when VREF=1.1V, IOSC1=10uA (typ)
and COSC1=100pF
 Coil current
1.1
5 0.22
1.0
 Chopping frequency
10 10
100 10
 STEP signal off detection time
1500 10
0.6
100
0.4
10
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LV8728MR
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