L6256
TYPICAL APPLICATION DIAGRAM
SPINDLE
SP_CLK SP_C
SP_B SP_A
C_TAP
vpwr
nPOR
PWM
BEMF_DET
SCLK
SDIO
RSLEW R_SLEW
100KΩ
C2 47nF
POR_RC
nPOR
RPWM PWM_IN
33KΩ
BEMF_DET
SCLK
SDIO
SP_CLK SP_C
5
3
8
9
10
11
12
13
14
SP_P1
2
+
VCC V
-
RS
1.5Ω
3.3V
C3
22µF
esr 0.5Ω
RDIO 1.2KΩ
VCC
15
5V_GND
17
RREF2 120KΩ
RREF
62.5KΩ
REF_IN
35
QDRIVE
20
CUR_IN
22
VREG_IN
21
BYPASSC
16
Cbyp
10nF
33
H_VPWR
CHVPWR
100nF
37
FF_COMP
Cffc
470pF
SP_B
1
4
SP_G1
SP_A SP_P2 C_TAP
43
42
41
VC_PWR
24
CP_CAP D4
19
CPCAP
2.2µF
35V
18
CP_OUT
34
CPOUT 33nF
VDD
32
DAC
31
IO_VC
A_IN
30
PARK Rp1 51KΩ
27
A_OUT
25
Rp2
100KΩ
I_VC
26
B_OUT
23
44
6,7,29,39,40
SP_G2
GND
SH_OUT
38
Rsh
100KΩ
PWM_DC
36
28
CSELB
Rpwindc
100KΩ
CSelB (from µP)
D97IN573
C1
4.7µF
25V
D5
D1
+
V VDD
-
Ra
1.5KΩ
Rb
4.3KΩ
Rfb
120KΩ
Cfb
390pF
RSENSE
0.75Ω
I_VC
B_OUT
VCM
Csh
3.3nF
Cdc
10nF
DESIGN FORMULAS:
1. Spindle Run Mode Slew Rate:
SR
=
1500 ⋅ 103
Rslew
(Volts
/µs)
2. Feedforward Compensation:
Fpwm
=
1
Tpwm
=
Cffc
1
⋅ Rslew
(Hz)
Dout
=
Tpwm
Tpwm+ 0.7µs
⋅
Vref
Vrslew
⋅
Din
Vref =
Rpwmdc
Rpwm
⋅ 2.47
(V)
Vrslew =
(Vpwr + 0.8)
1.86
(V)
Fpwm = PWM chopping frequency
Din = Input duty cycle at pwm_in
Dout = Spindle output duty cycle
4/28
3. Current Limit:
Ilimit
=
20
⋅
103
⋅
Vcc
Rref
(A)
4. BEMF Zero Crossing Detector:
- Slope Compensation: Csh ⋅ Rsh =
5.9683
(sec)
Vbemf = Amplitude of bemf
Vbemf⋅ N
N = Run mode speed of the motor in RPM
- Window width:
tw in =
15404
⋅
Vcc ⋅
Rref +
Rref
Rref2
⋅
Vbemf
⋅
N
⋅
Polepair
(µs)
5. VCM PARKING VOLTAGE:
VA,park
=
0.5
⋅
1
+
Rp2
Rp1
(V)
6. 3.3V REGULATOR:
Max Load Current:
IMAX
=
0.3
Rs
(A)