Page 1
CXA1940N
For the availability of this product, please contact the sales office.
4ch. Read/Write Amplifier for Thin Film Head of Hard Disk Drive
Description
The CXA1940N is a Read/Write Amplifier for the
thin film head of hard disk drives and designed to
handle up to 4-channel heads.
Features
• Operate on single +5V power supply.
• Low power consumption.
Read : 95mW
Write (IW=20mA) : 130mW+IW × 5
Power save : 5.5mW
• Write current can be varied through an external
resistor. Built-in stabilizing circuit provides stable
current during voltage and temperature drift.
• Drives up to 4 heads.
• Designed for two-terminal thin-film or MIG heads.
• Built-in power save function.
• Read amplifier emitter follower output featuring
290 times gain (Typ.).
• Built-in Write unsafe detection circuit.
• Built-in supply voltage monitor circuit prohibits
incorrect Write during power on or abnormal
voltage.
• Built-in IC protection circuit for short of head and
GND.
• Differential input capacitance for Read : 14pF
(Typ.).
• Write data input minimum pulse width : 10ns
• Read data output become high impedance in write
mode to improve read data offset when switching
from write to read mode.
• Unselected head DC voltage is GND potential.
• Self switching damping resistance (RD=310Ω)
Block Diagram and Pin Configuration
1
GND
H0X
2
H0Y
3
H1X
4
H1Y
5
H2X
6
H2Y
7
H3X
8
H3Y
9
NC
10
20 pin SSOP (Plastic)
DRIVER
AMP
DRIVER
AMP
DRIVER
AMP
DRIVER
AMP
IC
PROTECTOR
MODE
CONTROL
WRITE
CURRENT
SOURCE
AMP
HEAD
SELECT
POWER
ON/OFF
DETECTOR
T-FF
WRITE
UNSAFE
DETECTOR
PS
20
19
R/W
WC
18
RDY
17
16
RDX
HS0
15
14
HS1
V
CC
13
WDI
12
WUS
11
Sony reserves the right to change products and specifications without prior notice. This information does not convey any license by
any implication or otherwise under any patents or other right. Application circuits shown, if any, are typical examples illustrating the
operation of the devices. Sony cannot assume responsibility for any problems arising out of the use of these circuits.
—1—
E93X03-TE
Page 2
Structure
Bipolar silicon monolithic IC
Function
Read, Write and Write unsafe detection for HDD, Power supply
ON/OFF detection.
Absolute Maximum Rating (Ta=25°C)
• Supply voltage VCC 7V
•Write current IW 25 mAo-p
• Operating temperature Topr –20 to +75 °C
• Storage temperature Tstg –55 to +150 °C
• Allowable power dissipation PD 375 mW
Recommended Operating Conditions
• Supply voltage VCC 5V±10 %
• Write current IW 5 to 20 mAo-p
CXA1940N
—2—
Page 3
Pin Description
No. Symbol Equivalent circuit Description
1 GND
CXA1940N
2 H0X
3 H0Y
4 H1X
5 H1Y
6 H2X
7 H2Y
8 H3X
9 H3Y
10 NC
11 WUS
2
4
6
8
3
5
7
9
2k2k
VCC
VCC
Head.
4 channels provided.
GND
Write unsafe detection output.
11
Open collector output. When it is
off in Write mode, it means an
error is detected.
GND
VCC
12 WDI
13 VCC
14 HS1
15 HS0
19 R/W
20 PS
Write data input.
12
At “High” → “Low”,
input is triggered.
2.1V
1.4V
GND
5V power supply
Head select signal input.
VCC
Selects one of 4 heads according
to Table 2.
14
15
19
20
2.1V
GND
Read/Write signal input.
At “High”: Read,
at “Low”: Write.
Power save signal input.
At “High”: Power save.
—3—
Page 4
No. Symbol Equivalent circuit Description
VCC
CXA1940N
16 RDX
17 RDY
18 WC
16
17
GND
VCC
Read Amplifier output.
A setting resistor for the write
current value is connected
18
1.25V
GND
between this pin and GND.
—4—
Page 5
CXA1940N
Electrical Characteristics (Unless otherwise specified, VCC=5V, Ta=25°C, Write current IW=20mA)
No. Item Measurement conditions Min. Typ. Max. Unit
Current consump-
1-1
tion for Read
Current consump-
1-2
tion for Write
Current consump-
1-3
tion for Power save
Digital input “Low”
2-1
input voltage
Digital input “High”
2-2
input voltage
Digital input “Low”
2-3
input current
Digital input “High”
2-4
input current
Write unsafe output
3-1
saturation voltage
Write unsafe output
3-2
leak current
Sym- SW Conditions
bol
1 2 3 4 5 6 7 8 9101112
IR
baaaabaaaaba
IW
baaaabaaaaaa
IP
baaaabaaaabb
VIL
VIH
IIL
aaaaaaaaaaaa
IIH
aaaaababbabb
VWUS
baaabcaaaaaa
IWUS
baaaecaaaaaa
Test point : I4
Test point : I4
Test point : I4
Digital input :
Pins 12, 14, 15, 19, 20
“High” applied voltage : 5V
“Low” applied voltage : 0V
Test point : I3, I5, I6, I7, I8
Output current : 1mA
Test point : V1
Test point : I2
12 19 26 mA
17 26 35
+IW +IW +IW
mA
0.6 1.1 1.5 mA
0.8 V
2.0 V
–20 µA
70 µA
0.5 V
20 µA
When VCC is lowered
from 5V in Write mode
Supply power
ON/OFF detector
4
threshold voltage
VTH
baaaabaaaaaa
and IW does not flow
anymore, VCC voltage is
set to VTHOFF. When
3.6 3.9 4.3 V
VCC is raised from 3V
and IW starts to flow, VCC
voltage is set to VTHON.
Write current setting
5
range
IW
baaaabaaaaaa
520
mAo-p
Write current
6
tolerance
Read amplifier
differential voltage
7
gain
Frequency
8
band width (–3dB)
∆Iw
baaaabaaaaaa
AV
baaacbaaabba
BW
baaacbaaabba
—5—
Input voltage SG1 :
1mVp-p, 300kHz
Load resistance (RDX,
RDY) : 1kΩ
Test point : V4 [Vp-p]
V4
AV=
SG1
Frequency at which AV
lowers by 3dB
-8 8 %
245 290 335 V/V
30 MHz
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CXA1940N
No. Item Measurement conditions Min. Typ. Max. Unit
Sym- SW Conditions
bol
1 2 3 4 5 6 7 8 9 101112
Head impedance : 0Ω,
when the read amplifier
output voltage is
amplified 100 times and
voltage passed though
Input referred
9
noise
EN
aaaaabaaabba
a LPF (low pass filter of
cutoff frequency
0.55 0.7
nV
Hz
15MHz) is VN [Vrms],
EN=
VN
100 • AV • 15 × 10
6
Test point : V5
In-phase input voltage
SG2 : 100mVp-p, 5MHz
When the Read
amplifier output is VCM
Common mode
10
CMRR
baaadbaaabba
[mVp-p],
50 dB
rejection ratio
CMRR=20 log
+20 log AV
100
VCM
Power Supply
11
rejection ratio
Channel
12
separation
Read data
13
output offset
voltage for Read
PSRR
CS
VOFFR
aaaaabbaabba
abaacbaaabba
baaaabaaaaba
Test point : V4
Ripple voltage SG3 :
100mVp-p, 5MHz
When the Read
amplifier output is VP
[mVp-p],
PSRR=20 log
+20 log
100
V
P
Test point : V4
Selected head input
voltage : 0mVP-P
Unselected head input
voltage SG1 : 100mVp-p,
5MHz
When the Read amplifier
output is VCS [mVp-p],
CS=20 log
+20 log AV
100
VCS
Test point : V4
VOFFR=V2–V3
Test point : V2, V3
50 dB
50 dB
–200 200 mV
—6—
Page 7
CXA1940N
Unless otherwise specified, VCC=5V, Ta=25°C, fWD (Write data frequency)=5MHz, IW=20mA, LH (Head
inductance)=1µH, RH (Head DC resistance value)=30Ω
Refer to Fig. 2 to Fig. 4
No. Item Measurement conditions Min. Typ. Max. Unit
Head differential
14
voltage amplitude
Write unsafe
15
detection max.
Sym-
bol
VSW
FWUS
Differential voltage between HX pin and HY pin
at switching of Write current
FWUS is the max. Write data frequency when Pin
11 turns “High” in Write mode.
4.4 5.2 Vp-p
280 1000 kHz
frequency
Mode switching time
16-1
Read to Write
TRW is the time required for Write current to turn
TRW
to 90% after Pin 19 changes from “High” to
0.6 µs
“Low”.
Mode switching time
16-2
Write to Read
TWR is the time required for either Write current
TWR
to decrease to 10% or for the Read amplifier
0.6 µs
output∗to turn to 90% after Pin 19 changes from
“Low” to “High”.
Mode switching time
17-1
safe to unsafe
TSA1
TSA1 is the time required for Pin 11 to turn “High”
after the last transition of Write data when Write
3 7 11 µs
data is stopped in Write mode.
Mode switching time
17-2
unsafe to safe
Mode switching time
18
Power save to Read
TSA2
TSA2 is the time required for Pin 11 to turn “Low”
after the first transition of Write in Write mode.
TPR is the time required for Read amplifier
TPR
output to turn to 90% after Pin 20 changes from
1.0 µs
1.0 µs
“High” to “Low”.
Head switching time
19
TH is the time required for the Read amplifier
TH
0.6 µs
output∗to reach 90% when the selected head
switched in Read mode.
Write current
20
propagation delay
time
Write current rise/fall
21
time
TR/TF
TPD is the time required for Write current to
TPD
reach 90% after the Write data falling edge.
LH=0µH, RH=0Ω
TR is the time required for Write current to reach
90% from 10%; TF is the same time required to
30 ns
510ns
reach 10% from 90%. LH=0µH, RH=0Ω
∗Read amplifier output 100mVp-p 10MHz
—7—
Page 8
Test Circuit 1
CXA1940N
V
V5
LPF
to 15MHz
×100
AMP
×1
AMP
V
V4
5V
S12 S11
A
A
I8 I7 I6 I5 I3 I2
8.2k
1k1k
SG3
1µ
1µ
V3 V2
V
V
ababaab ab b ab
S10
S9 S8
A
A
VCC
5V
b
A
a
S7
500kHz
1 2 3 4 5 6 7 8 9 10
S1 S2 S3
ab ab ab
ab ab ab ab ab
S5
S4
V
5V
CC
PG
PG1
1µ
V1
5.1k
V
A
111213141516171820 19
I4
5V
0V
bca
S6
A
Test Circuit 2
abcd a bcd
PG PG
ee
0.1µ
SG2
0.1µ
1k1k
1µ
PG
×1
0.1µ
AMP
A
I1
33
SG1
1µ
8.2k
5V
5V
PG
0V
1 2 3 4 5 6 7 8 9 10
1µH1µH1µH
1µH
Fig. 1
1µ
5.1k
111213141516171820 19
Fig. 2
Note) Write current is measured with current probe. Use an oscilloscope to test items related to time.
—8—
Page 9
Timing Chart 1
WDI
CXA1940N
R/W
PS
IWX
IWY
RDX
RDY
Timing Chart 2
90%
50%
TRW
10%
90%
Fig. 3
90%
50%
TWR
TWR
50%
10%
TPR
90%
WDI
IWX
IWY
WUS
50%
TPD
90%
TSA2
10%
90% 90%
TR
50%
10%
TF
Fig. 4
—9—
50%
TSA1
50%
Page 10
CXA1940N
Description Functions
Read amplifier
This is a low noise amplifier amplifying the signals from the head and is an emitter follower output. It outputs
to RDX and RDY pins differentially. The head X side and RDX pin, the head Y side and RDY pin have the
same polarity. RDX, RDY outputs become high impedance in write mode (when these outputs is AC coupled
to the load).
Write circuit
Write data which is input to WDI pin passes through a T flip-flop and frequency is divided into 1/2. It then
drives the Write switch circuit and flows Write current to the head.
Write data is triggered where from “High” to “Low” and Write current is switched.
Write current flows from X side when Read changes to Write.
Mode control
Modes are set as shown in Table 1 using R/W and PS pins.
R/W PS Mode
L L Write
H L Read
H H Power save
Table 1. Mode selection
Head selection
Heads are selected as shown in Table 2 using HS0 and HS1 pins.
HS0 HS1 Head
LL 0
HL 1
LH 2
HH 3
Table 2. Head selection
—10—
Page 11
CXA1940N
Write unsafe detection circuit
Abnormal Write mode is detected.
In normal Write mode, WUS output turns to “Low” and in the following other conditions, WUS output turns to
“High”.
• Head input is open.
• Head input is shorted to GND.
• Write data frequency is abnormally low.
• No write current
• In read
• In power save
Power supply ON/OFF detection
VCC is monitored to avoid incorrecting Write.
Recording and Playback functions are inhibited as detected as abnormal when VCC decreases below the
power supply ON/OFF detector threshold voltage (VTH). When VCC is higher than VTH, the above inhibition is
released.
—11—
Page 12
Application Circuit
PULSE
DETECTOR
CXA1940N
+5V
1µ
RW
8.2k
5.1k
111213141516171820 19
1 2 3 4 5 6 7 8 9 10
L
H LH LH LH
1µH1µH1µH1µH
Application circuits shown are typical examples illustrating the operation of the devices. Sony cannot assume responsibility for any problems
arising out of the use of these circuits or for any infringement of third party and other right due to same.
NC
—12—
Page 13
CXA1940N
Notes on operation
• This device handles high frequency and high gain signals. Please note the following;
♦ Connect VCC decoupling capacitor of approximately 1000pF near the device.
♦ Make the GND area as large as possible.
• When using as 2-channel, short-circuit the X and Y sides of unused head pins or leave them open.
• Write data pulse width
Set the pulse width to 10ns or more at 1.5V to prevent misoperation.
• The WC pin is a constant voltage pin. When noise affects this pin, it creates noise in Write current.
Therefore, locate RW as close to the device as possible .
• Write unsafe detection circuit
This circuit uses the voltage waveforms of the head pins for detection.
Wave form of write data
Voltage waveform
of head pins (HX, HY)
1.5V
T1
VTH=2VVFB
VTH
GND
♦ The condition of T1 >10ns must be met for the WUS detection circuit to operate properly.
♦ VFB must be more than 2V. When VFB < 2V, it is possible that Write unsafe detection maximum
frequency becomes more than 1MHz.
♦ The normal operating area of write unsafe detection circuit is changed by head inductance, head DC
resistance, write current and other.
—13—
Page 14
Application Notes
Use the following characteristics for reference.
Item Conditions Min. Typ. Max. Unit
Differential output capacitance
Write mode
Differential output resistance
Differential input capacitance
Read mode
Differential input resistance
Output resistance
Sym-
bol
CO
Between head input pins
RO
Between head input pins
CI
f=5MHz
RI
RRD
RDX or RDY, f=5MHz
CXA1940N
VCC=5V, Ta=25°C
15 pF
230 310 390 Ω
14 20 pF
0.7 1.4 kΩ
40 60 Ω
Unselected head differential current in
IUS
Write mode
∗
Write current symmetry
∗
TAS=T1—T2
TAS
50% 50% 50%IWX+IWY
T1 T2
Setting of Write current
Write current can be set with resistor Rw (kΩ) at Pin 18.
Iw=K/Rw (mA) Refer to Fig. 5 and 6.
Fig.5 Write current vs. RW
148
LH=1µH, RH=30Ω
Iw=20mA
LH=0µH, RH=0Ω
Iw=20mA
Fig. 6 Write current setting constant vs Write current
WC
18
–1 1 ns
W
R
0.2 mAp-p
20
10
-Write current (mA)
W
I
5
510 20
RW (KΩ)
K=Rw • I
146
144
142
Write current setting constant K
30
140
5101520
Write current IW (mA )
W
—14—
Page 15
CXA1940N
Fig.7 Normalized write current vs Supply voltage
1.01
=5 V)
CC
1.00
(V
W
/I
W
I
0.99
4
5
Supply voltage V
CC (V )
Fig. 9 Normalized read amplifier voltage gain
vs Supply voltage
1.02
6
Ta=25°C
Ta=25°C
Fig. 8 Normalized write current
vs Ambient temperature
CC=5V
V
1.01
1.00
(Ta=25°C)
W
0.99
/I
W
I
0.98
7
–25
025
50
75
Ambient temperature Ta (°C)
Fig. 10 Normalized read amplifier voltage gain
vs Ambient temperature
VCC=5V
1.01
=5V)
CC
1.00
(V
V
/A
V
A
0.99
4
56
Supply voltage VCC (V)
Fig. 11 Power supply ON/OFF detector threshold
voltage vs Ambient temperature
4.0
OFF→ON
1.01
1.00
(Ta=25°C)
V
/A
0.99
V
A
0.98
7
–25
025
50
75
Ambient temperature Ta (°C)
3.9
ON→OFF
3.8
Detector Threshold Voltage (V)
Power supply ON/OFF
–25
025
50 75
Ambient temperature Ta (°C)
—15—
Page 16
Package Outline Unit : mm
CXA1940N
20PIN SSOP (PLASTIC)
∗6.5 ± 0.1
20
1
+ 0.1
0.22 – 0.05
NOTE: Dimension “∗” does not include mold protrusion.
11
∗4.4 ± 0.1
10
0.65 ± 0.12
0° to 10°
A
+ 0.05
0.15 – 0.02
DETAIL A
0.1 ± 0.1
0.5 ± 0.2
+ 0.2
1.25 – 0.1
6.4 ± 0.2
0.1
SONY CODE
EIAJ CODE
JEDEC CODE
SSOP-20P-L01
SSOP020-P-0044
PACKAGE STRUCTURE
PACKAGE MATERIAL
LEAD TREATMENT
LEAD MATERIAL
PACKAGE WEIGHT
EPOXY RESIN
SOLDER / PALLADIUM
COPPER / 42 ALLOY
0.1g
PLATING
—16—
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