BLOCK DIAGRAMS vee GNO

ABSOLUTE MAXIMUM RATINGS Power Supply: Junction Temperature ... 150°C Storage Temperature Tstg ... -65° to 150°C Thermal Characteristics, 9JA:

20-lead SOIC ... 90°CIW 2Q-lead SSOP ... 110°CIW 36-lead SOIC ... 80°CIW

RECOMMENDED OPERATING CONDITIONS Power Supply Voltage:

Vee ... +5V

±

10%

Write Current (lw) ... 1 to 40mA Head Inductance (LH) ... 0.2 to 51lH Junction Temperature (TJ) ... 25°C to 125°C

CIRCUIT OPERATION

The VM7162 addresses two two-terminal thin-film heads, pro-viding write drive or read amplification. Head selection and mode control are accomplished with pins WSER, HSO,

CS

and

RiW,

as shown in Tables 1a and 2a.

The VM7164 addresses four two-terminal thin-film heads, pro-viding write drive or read amplification. Head selection and mode control are accomplished with pins WSER, HSO, HS1,

CS

and

RIW,

as shown in Tables 1b and 2b.

The VM7168 addresses eight two-terminal thin-film heads, providing write drive or read amplification. Head selection and mode control are accomplished with pins HSO, HS1, HS2, WSER,

CS

and

RiW,

as shown in Tables 1c and 2c.

On all versions, intemal pull-up resistors on pins CS and

RiW

will force the device into a non-writing condition if either control line is opened aCCidentally.

Write Mode

In write mode, the VM7160 acts as a write current switch with the write Unsafe (WUS) detection circuitry activated. Write cur-rent is toggled between the X and Y side of the selected head on each high to low transition on the Write Data Flip-Flop (WOFF) so that upon switching to the write mode, the write current flows into the "X" side of the head.

The write current magnitude is determined by an extemal resistor (RWC) connected between the WC pin and Ground. An intemally generated reference voltage is present at the WC pin.

The magnitude of the Write Current (O-PK,

±

8%) is:

Iw

=

Kw/Rwe + 0.2mA

=

5O/Rwe + 0.2mA

VTC Inc.,'2800 East Old Shakopee Road. Bloomington. MN 55425. 612-853-5100

Power supply fault protection ensures data security on the disk by disabling the write current source during a power supply volt-age fault or by supply power up/down conditions. Additionally, the write unsafe (WUS) detection circuitry will flag any of the conditions listed below, as a high level on the WUS line. Two negative transitions on the WOI pin, after the fault is corrected, is required to clear the WUS line.

• No write current

• WOI frequency too low

• Read or sleep mode Servo Write Mode

In servo write mode, two channels of the VM7162 are active at the same time. Pin WSER controls the servo mode. When WSER and

RIW

are low, the chip is in servo write mode, where both heads are written independent of the head select line (see table 1 a). When WSER is high and

RIW

is low, the chip is in nor-mal write mode: one head is written at a time based on the state of the head select line.

In servo write mode, four channels of the VM7164 are active at the same time. Pin WSER controls the servo mode. When WSER and

RIW

are low, the chip is in servo write mode: four channels are written at the same time, independent of the head select lines (see table 1b). When WSER is high and

RIW

is low, the chip is in normal write m'ode: one head is written at a time based on the state of the head select lines.

In servo write mode, four channels of the VM7168 are active at the same time. Pin WSER controls the servo mode and HSO controls which four heads are simultaneously written. When WSER and RiW are low, the chip is in servo write mode: four channels are written at the same time dependent on the state of HSO. When HSO

=

0, heads 0, 2, 4 and 6 are written and when HSO

=

5V, heads 1,3,5 and 7 are written (see Table 1c). When WSER is high and

RIW

is low, the chip is in normal write mode:

one head is written at a time based on the state of the head select lines.

On all versions, an internal pull-up resistor on pin WSER will force the device into single head write mode if the control line is accidentally opened.

Read Mode

In read mode, the VM7160 acts as a low noise differential amplifier for signals coming off the disk. The write current gen-erator and write unsafe circuitry is deactivated. The RDX, ROY pins are emitter follower outputs and are in phase with "X" and

"Y" head ports. These outputs should be AC coupled to the load.

The ROX, ROY common mode output voltage is constant, mini-mizing the transient between read and write mode, thereby, substantially reducing the recovery time in the Pulse Detector circuit connected to these outputs.

Sleep Mode

When CS is high, initially all circuitry is shut down so that power dissipation is reduced to 4.5 mW in the sleep mode.

Switching the

CS

line low wakes up the chip and the device will enter the read or write mode, depending on the status of the RlWline.

VTC Inc" 2800 East Old Shakopee Road, Bloomington, MN 55425, 612·853-5100

- - - -

-Diode Connected Damping Resistor (patent pending) The VM7162 has damping resistors isolated by Schottky diodes. The diodes effectively remove the resistor from the cir-cuil during the read mode, however during the write mode with the higher level input signal, the resistor provides damping for the write current waveform.

Input Structure:

Please consult factory for damping resistor options on other devices.

Table 1 a: Mode Selection for VM716N2

RlW CS WSER MODE

0 0 0 Write Single

1 0 X Read

X 1 X Idle

0 0 1 Write Servo (head 0, 1)

Table 1 b: Mode Selection for VM716N4

RIW CS WSER MODE

0 0 0 Write Single

1 0 X Read

X 1 X Idle

0 0 1 Write Servo (head 0,1,2,3)

Table 1 c: Mode Selection for VM7158

RIW

CS WSER HSO MODE

Table 2a: Head Selection in Single Write Mode (WSER

=

HIGH) for VM716N2

HSO HEAD

0 0

1 1

Table 2b: Head Selection in Single Write Mode (WSER

=

HIGH) for VM716N4

HS1 HSO HEAD

0 0 0

0 1 1

1 0 2

1 1 3

Table 2c: Head Selection in Single Write Mode (WSER

=

HIGH) for VM7168

HS2 HS1 HSO

0 0 0

0 0 1

0 1 0

0 1 1

1 0 0

1 0 1

1 1 0

1 1 1

2-124

HEAD 0 1 2 3 4 5 6 7

PIN DESCRIPTIONS

NAME VO DESCRIPTION

HSO - HS2 I· Head Select: selects one of up to eight heads

HOX- H7X

I/O X,Y Head Terminals HOY- H7Y

Write Data Input: TTL input signal, WDI I· negative transition toggles direction

of head current

Chip Select: high level signal puts

CS

I chip in sleep mode, low level wakes chip up

ReadiWrite Select: high level

R/W

^I· selects read mode, low-level selects write mode

Write Unsafe: open collector output:

WUS O· high level indicates writes unsafe condition

we

Write Current Adjust: a resistor adjusts level of write current RDX- ROY O· Read Data Output: differential

output data

vee

+5V Supply··

GND Ground

WSER I· Servo Write: a high level enables servo mode.

• May be wire-OR'ed for multi-chip usage.

•• Although both

vee

connections are recommended, only one connection is required as both are connected-internally.

VTC Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425, 612-853-5100

If'

VM7160

^~

..

'i'.~

~:~

DC CHARACTERISTICS Recommended operatong conditions apply, unless otherwise specified.

PARAMETER SYM CONDITIONS MIN TYP MAX UNITS

(Note 1)

Read Mode, Iw = 20mA 39 + 0.251w 49+0.25Iw Write Mode, Iw = 35mA

44+lw 52+ Iw Normal, VM7162

Power Supply Current Icc Normal, VM7164 & VM7168 54+lw 64+ Iw mA

Servo, VM7162 44+2Iw 56+21w

Servo, VM7164 & VM7168 70+41w 82+41w

Read Mode 220 297

Power Dissipation Write Mode, Iw = 35mA

395 479

PD Normal mW

VM7162

Servo 570 693

Sleep Mode 0.6 3

Read Mode 220 297

Power Dissipation Write Mode, Iw = 35mA

445 545

PD Normal mW

VM7164 & VM7168

Servo 1050 1221

Sleep Mode 3 17

Input High Voltage VIH 2 Vcc+ 0.3 V

Input Low Voltage VIL -0.3 0.8 V

Input High Current IIH VIH =2.7V 80 !LA

Input Low Current IlL VIL =O.4V -160 !LA

WUS Ouput Low Voltage VOL IOL=4.0mA 0.35 0.5 V

WUS Output High Current IOH VOH =5.OV 13 100 !LA

VCC Value for Write Current Turn

IH <0.2mA 3.7 4.0 4.3 V

Off

Note 1: Typical values are given at V cc = 5V and T A = 25°C.

VTC Inc .• 2800 East Old Shakopee Road, Bloomington. MN 55425. 612-853-5100 2-125

READ CHARACTERISTICS Recommended operating conditions apply unless otherwise specilied, CL (RDX, RDY) < 20pF, RL (RDX, RDY)

=

^{1 kil.}

TYP

.

PARAMETER SYM CONDITIONS MIN

(Note 1) MAX UNITS

VIN

=

1mVrms, 1MHz, VM7162 250 300 350

Differential Voltage Gain Av VIN

=

1mVrms, 1MHz, VM7164 250 300 350 VN

VIN

=

1mVrms, 1MHz, VM7168 210 250 290 -1dB IZsl < 50, VIN

=

1mVp-p 30 40

Bandwidth BW MHz

-3dB IZsl < 50, VIN

=

1 mVp-p 55 75

Input Noise Voltage ein BW

=

^{17MHz, LH}

=

^{0, RH}

=

^{0 0.53 0.75 nV/..fHz}

Differential Input Capacitance CIN VIN

=

1mVp-p, 1

=

5MHz 18 22 pF

Differential Input Resistance RIN VIN

=

1 mVp-p, 1

=

5MHz 380 1000 0

Dynamic Range DR AC input where Av is 90% 01 gain

2 5 mVrms

at 0.2mVrms input

Common Mode Rejection Ratio CMRR VIN

=

^{100mVp-p @ 5MHz 50 70} dB

Power Supply Rejection Ratio PSRR 100mVp-p @ 5MHz on Vcc 45 63 dB

Channel Separation CS Unselected channel driven with

45 55 dB

20mVp-p @ 5MHz

Output Offset Voltage Vos -250 250 mV

RDX, RDY Common Mode Output

VOCM Read Mode Vcc - 2.7 V

Voltage

Read to Write Common Mode

/NOCM -350 50 350 mV

Output Voltage Difference

Single-Ended Output Resistance RSEO 16 35 0

Output Current 10 AC coupled load, RDX to RDY ±1.5 rnA

Note 1: Typical values are given at V cc

=

^{5V and T A}

=

^25°C.

2-126 VTC Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425. 612·853-5100

WRITE CHARACTERISTICS Recommended operating conditions apply unless otherwise specified, LH = 1 ~H, RH = 30n, Iw = 20mA, fDATA = 5MHz.

PARAMETER SYM CONDITIONS MIN TYP MAX UNITS

(Note 1)

WC Pin Voltage Vwe 2.5 V

Iwe to Head Current Gain AI 20 mA/mA

Write Current Constant Kw Kw = (Vwcl(AI), 10 - 30mA 46 50 54 V

Write Current Range Iw 1.44K < Rwe < 10.4K 5 35 mA

Write Current Tolerance AIW Iw=5-35mA -8 8 %

Differential Head Voltage Swing VDH 4.5 5.2 Vp-p

WDI Transition Frequency for Safe

fDATA WUS = low 1 MHz

Condition

Differential Output Capacitance COUT 15 pF

Differential Output Resistance ROUT 3200 n

Unselected Head Transient Current IUH 0.15 1 mA(pk)

RDX, ROY Common Mode Output

VeM Vee - 2.7 V

VClltage

Note 1: Typical values are given at Vee = 5V and T A = 25°C.

VM7162 (Two Channels), VM7164 and VM7168 (Four Channels) Write

PARAMETER SYM CONDITIONS MIN TYP MAX UNITS

Write Current Matching Between

AIW 5mA < Iw < 35mA . 10 %

Channels

Duty Cycle (25mA/head) 20 %

Note 1: Typical values are given at Vee = 5V and T A = 25°C.

VTe Inc., 2800 East Old Silakopee Road. Bloomington. MN 55425. 612·853-5100 2-127

~~

_~,#

_VM7160

SWITCHING CHARACTERISTICS Recommended operating conditions apply unless otherwise specified; Iw = 20mA, fDATA = 5MHz, LH = 11!H, RH = 30n, CL (RDX, RDY) ~ 20pF (see Figure 1).

PARAMETER

RIW Read to Write Delay RiW Write to Read Delay

WSER to Read Delay

CS

Unselect to Select Delay CS Select to Unselect Delay HSO - HS2 any Head Delay WUS Safe to Unsafe Delay WUS Unsafe to Safe Delay Head Current Propagation Delay Head Current Asymmetry

Head Current Rise/Fall Time

HEAD CURRENT

SYM

tRW tWR tSR

tlR tRI tHS tD1 tD2 tD3 ASYM

t,ltf

Figure 1: Write Mode Timing Diagram

CONDITIONS MIN TYP MAX

(Note 1)

R1Wt090% Iw 0.04 0.3

RIW to 90% of 100mV, 10 MHz

0.4 1

read signal envelope RIW to 90% of 100mV, 10MHz

0.4 1

read signal envelope

CS to 90% Iw or 90% of 100mV,

0.15 0.6

10MHz read signal envelope

CS to 10% of Iw 0.05 0.6

HSO - HS2 to 90% of 100mV,

0.03 0.6

10MHz read signal envelope

0.6 2.1 3.6

1.0

LH = 0, RH = 0, from 50% points 30

50% duty cycle on WDI,

0.04 0.5

1 ns rise/fall time; LH = 0, RH = 0 10% to 90% pOints, LH = 0,

1.9 5

RH=O

10% to 90% points, LH = 11!H,

12 16

RH=30n

UNITS

I!s

!!S

!!S I!s

!!S

!!S

!!S

!!S ns ns

ns

2-128 VTC Inc:, 2800 East Old Shakopee Road, Bloomington, MN 55425,612-853-5100

~~ ~~'~"l

_,:.:~

VTC Inc.

Value the CustomsrTM

FEATURES

• High Performance

- Read Gain

=

³⁰⁰ VN Typical - Input Noise 0.75 nV/..fHZ Maximum

- Head Inductance Range

=

0.4 - 51lH (1 IlH typical) - Write Current Range 5 - 35 rnA

- Input Capacitance

=

18pF Maximum (14 pF typical)

• TLL Write Data Input

• Servo Write Four Channels at the Same Time

• Very Low Power DiSSipation

=

4.5 mW Typical in Sleep Mode

• Power Up/Down Data Protect Circuitry

• Fast Write-ta-Read and Read-to-Write Recovery Time

• Single Power Supply

=

^{5 V}

^±

^10%

• Fault Detect Capability

• Designed for 2-Terminal Thin-Film or MIG Heads

• Other Read Gain Options Available

• Available in 4-Channel DESCRIPTION

The VM7164S is a high-performance, very low-power read!

write preamplifier designed for use with external 2-terminal, thin-film or MIG recording heads. This circuit will operate on a single 5-volt power supply and is ideally suited for use in battery pow-ered disk drives. The VM7164S provides a four channel servo write feature, enabling the user to write servo information directly through the preamp.

The VM7164S provides write current switching in the write mode and a low noise data path in the read mode for up to four read/write recording heads. When deactivated, the device enters a sleep mode that reduces power diSSipation to 4.5 mW.

Data protection circuitry is provided to ensure that the write cur-rent source is totally disabled during power supply power up/

power down conditions. Write-to-read recovery time is mini-mized by eliminating common mode output voltage swings when switching between modes.

The VM7164S is available in several different packages.

Please consult VTC for package availability and additional read mode voltage gains.

VTC Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425, 612-853-5100

VM7164S

4-CHANNEL, 5-VOL T, THIN-FILM

Dans le document Gain of ~ (Page 187-194)