RECOMMENDED OPERATINC CONDITIONS DC Power Supply Voltage:

10-CHANNEL, HIGH-PERFORMANCE, THIN-FILM HEAD, READIWRITE

RECOMMENDED OPERATINC CONDITIONS DC Power Supply Voltage:

Voo ... 12V ± 10%

Vee ... 5V± 10%

Junction Temperature ... O°C to 125°C

2-24

CIRCUIT OPERATION

The VM313 addresses ten two-terminal thin film heads, pro-viding write drive or read amplification. Head selection and mode control are accomplished with pins HSn,

CS

and RiW, as shown in Tables 1 and 2. Internal resistor pull ups provided on pins CS and

RiW

will force the device into a non-writing condi-tion if either control line is opened accidentally.

Write Mode

Write mode configures the VM313 as a current switch and acti-vates the write unsafe (WUS) detection circuitry. Write current is toggled between the X and Y direction of the selected head on each high-to-Iow transition on pins WDI - WDI (differential write data inputs).

A preceding read operation initializes the write data flip-flop (WDFF) so that upon entering the write mode current flows into the "X" head port.

The write current magnitude is determined by an external resistor connected between the WC pin and ground. An inter-nally generated 1.71 V reference voltage is present at the WC pin. The magnitude of the write current (O-pk, ± 8%) is:

Iw = 1.65 V/Rwe

Typically, an adjustment to the calculated head current is required to account for current shunted by the damping resistor.

This complication is avoided in the VM313 because the internal damping resistors are series-connected with Schottky diode pairs.

In multiple-device applications, a single Rwe resistor may be made common to all devices.

Power supply fault protection improves data security by dis-abling the write current generator during a voltage fault or power supply sequencing. Additionally, the write unsafe detection cir-cuitry will flag any of the conditions listed below with a high level on the open collector output pin, WUS.

• No write current

• WDI frequency too low

• Open head

• Device in read mode

• Device not selected

Two negative write data transitions, after the fault is corrected, may be required to clear the WUS flag.

Read Mode

Read mode configures the VM313 as a low-noise differential amplifier and deactivates the write current generator and write unsafe detection circuitry. The RDX and RDY outputs are emit-ter followers and are in phase with the "X" and "Y" head ports.

These outputs should be AC coupled to the 10!ld. The RDX, RDY common-mode voltage is maintained in the write mode, minimizing the transient between write mode and read mode, substantially reducing the recovery time delay to the subsequent Pulse Detection circuitry.

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

Idle Mode

When

'OS

is high, virtually the entire circuit is shut down so that power dissipation is reduced to less than 180mW for a sleep mode. Multiple devices may have their read outputs wire OR'ed together and the write current programming resistor common to all devices.

Table 1: Mode Select

RIW

~ MODE

0 0 Write

1 0 Read

X 1 Idle

Table 2: Head Select

HSO HS1 HS2 HS3 HEAD

0 0 0 0 0

1 0 0 0 1

0 1 0 0 2

1 1 0 0 3

0 0 1 0 4

1 0 1 0 5

0 1 1 0 6

1 1 1 0 7

0 0 0 1

,

⁸

1 0 0 1 9

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

PIN DESCRIPTIONS

NAME VO DESCRIPTION

HSO- HS3 I" Head Select: selects one of up to ten heads

HOX- H9X

1/0 X, Y Head Terminals HOY- H9Y

Write Data Input: A negative transition WDI,WDi I" (WDI - WDI) toggles direction of head

current.

CS

I Chip select: low level enables th~

device

ReadlWrite select: high level selects

RiW

I" read mode, lOW-level indicates writes unsafe condition

Write Unsafe: open collector output, WUS 0" high level indicates writes unsafe

condition

"

Write Current: a resistor adjusts level of write current

RDX,RDY 0" ^{Read Data}^O~tput:differential output data

VCC

+5

volt logic circuit supply VDD

+

12 volt supply

GND Ground

" When more than one

R/W

device is used, these signals can be wire OR'ed.

TYPICAL APPLICATION

+5V +12V

O.01I'F

ROX ^O.01I'F

~t

^OUlpUI

ROY

1kn ·1kn WDI PECL Level"

VM313

WOI

}=-ANI HSO HS1 HS2 GNO HS3

" For proper operation in read or write mode the WDIIW1:iT inputs must be correctly biased to their respective PECl levels.

They cannot float of both be tied high or low.

2-25

DC CHARACTERISTICS Unless otherwise specified, recommended operating conditions apply.

PARAMETER SYM CONDITIONS MIN TYP MAX UNITS

Read Mode 47

VCC Supply Current Icc Write Mode 27 mA

Idle Mode 4

Read Mode 31

VDD Supply Current ₁₀₀ Write Mode 30+ Iw mA

Idle Mode 12

Read Mode 500 670

Power Dissipation (TJ = 125°C) Po Write Mode: Iw=20mA 625 800 mW

Idle Mode 105 180

Input Low Voltage VIL . TTL O.B V

Input High Voltage VIH TTL 2.0 V

Input Low Current IlL VIL = O.BV, TTL -0.4 mA

Input High Current IIH VIH = 2.0V, TTL 100

IlA

WDI, WDI Input High Voltage VIH Pseudo ECL Vee -1.0 Vee- 0.7 V

WDI, WDI Input Low Voltage VIL Pseudo ECL Vee- 1.9 Vee -1.6 V

WDI, WDllnput High Current IIH VIH = Vee - 0.7V 100

IlA

WDI, WDllnput Low Current IlL VIL = Vee -1.6V BO

IlA

WUS Output Low Voltage VOL IOL=BmA 0.5 V

VCC Fault Voltage VOOF 9.0 10.5 V

VCC Fault Voltage VeeF 3.5 4.3 V

Write Mode, 0 < Vee $ 3.5V,

-200 +200

0< Voo < 9V

Head Current (HnX, HnY) IH

IlA

Write Mode, 0 < Vee < 5.5V,

-200 +200

0< Voo < 13.2V

2-26 VTC Inc .• 2800 East Old Shakopee Road, Bloomington, MN 55425, 612-853-5100

READ CHARACTERISTICS Unless otherwise specified, recommended operating conditions apply, CL (RDX, RDY) < 20pF and RL (RDX, RDY) = 1kO.

PARAMETER

SYM

CONDITIONS MIN TYP MAX UNITS

Differential Voltage Gain Av VIN = 1mVp-p @300kHz 125 175 VN

-1dB, IZsl < 50, VIN = 1mVp-p

@300kHz 25

Bandwidth BW MHz

-3dB, IZsl < 50, VIN = 1mVp-p

@300kHz 45

Input Noise Voltage ein BW = 15MHz, LH = 0, RH = 0 0.65 O.S nVlVHz

Differential Input Capacitance CIN VIN = 1 mVp-p, f = 5MHz 17 26 pF

Differential Input Resistance RIN VIN = 1 mVp-p, f = 5MHz,

500 1000 0

(25°C < TA < 125°C)

AC input voltage where the gain

Dynamic Range DR falls to 90% of the gain @ 2 mVrms

0.2mVrms input, f = 5MHz

Common Mode Rejection Ratio CMRR VeM = 100mVp-p @5MHz 54 dB

Power Supply Rejection Ratio PSRR 100mVp-p @5MHz on

54 dB

VooorVee

Unselected channels driven with

Channel Separation CS 100mVp-p @5MHz, Selected 45 dB

Channels VIN = OmVp-p

Output Offset Voltage VOS -250 +250 mV

RDX, RDY Common Mode Output Read Mode Vee- 2.S Vcc -2.3 Vee- 2.O

Voltage VOeM V

Write Mode Vee- 2.S Vee -2.3 Vee - 2.0

Single-Ended Output Resistance RSEO f = 5MHz 30 0

Output Current 10 AC coupled load, RDX to RDY 3.2 rnA

WRITE CHARACTERISTICS Unless otherwise specified, recommended operating conditions apply, Iw = 20mA, LH = 1.0~H, RH = 300 and fOATA = 5MHz.

PARAMETER

SYM

CONDITIONS MIN TYP MAX UNITS

WC Pin Voltage Vwe 1.65 V

Write Current Voltage VOH Iwe= 40mA 7 Vp-p

Unselected Head Current IUH 1.0 rnA (pk)

Differential Output Capacitance COUT 25 pF

Differential Output Resistance ROUT 3.2 ^kQ

WDI Transition Frequency fOATA WUS = low 1.7 MHz

Write Current Range Iw 41.250 < Rwe < 1650 10 40 rnA

Write Current Tolerance c.lw Iw range 10mA to 40mA -S +S %

VTC Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425, 612-853-5100 2-27

SWITCHING CHARACTERISTICS (see Figure 1) Unless otherwise specified, recommended operating conditions apply, Iw = 20mA, LH = 1.0ItH, RH = 30n and fOATA = 5MHz.

PARAMETER

RJW

to Write Mode

RJW

to Read Mode

CS to Select

CS to Unselect HSO - HS3 to Any Head Safe to Unsafe Unsafe to Safe Propagation Delay Asymmetry

Rise/Fall Time

WUS

HEAD CURRENT (iw)

SYM tRW

tWR

tlR

tlW tHS t01 t02 t03 ASYM

t,lt,

Figure 1: Write Mode Timing Diagram

CONDITIONS MIN TYP MAX

Delay to 90% of write current 0.6

Delay to 90% of 100mV, 10MHz

read signal envelope or to 90% 0.6

decay of write current

Delay to 90% of write current or

to 90% of 100mV, 10MHz read 0.6

signal envelope

Delay to 10% of write current 0.6

Delay to 90% of 100mV, 10MHz read signal envelope 0.4

50% WDI to 50% WUS 0.6 3.6

50% WDI to 50% WUS 1

From 50% pOints, LH = 0, RH = 0 32

WDI has 50% duty cycle and 1 ns rise/fall time, LH = 0, RH = 0 0.5 10% - 90% points, Iw = 20mA, LH= 0, RH = 0 5

10% - 90% points, Iw = 20mA, LH = 600nH, RH = 20n 9

UNITS IlS

its

its its its IlS ns ns

2-28 VTC Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425, 612·853·5100

~~.~ .~.

_~:.:~

^{VTC Inc.}

Value the Customer'"

FEATURES

• High Performance:

- Read Mode Gain

=

150 VN

• low Power Dissipation

• Enhanced System Write-to-Read Recovery Time

• Power Supply Fault Protection

• Schottky Isolated Damping Resistor Standard

• Write Unsafe Detection

• +5V and +12V Power Supply Requirement

• Differential PECl Write Data Inputs

• Pin-compatible with SSI32R2010 DESCRIPTION

The VM31316 is a high-performance, low-power, bipolar monolithic read I write preamplifier designed for use with two-ter-minal thin-film recording heads. It provides write current control, data protection circuitry and a low-noise read preamplifier for ten channels. When unselected, the device enters a sleep mode, with power dissipation reduced to less than 180mW. Fault pro-tection is provided so that during power supply sequencing the write current generator is disabled. System write-to-read recov-ery time is minimized by maintaining the read channel common-mode output voltage in the write common-mode.

Very low power dissipation from +5V and +12V supplies is achieved through use of high-speed bipolar processing and innovative circuit design techniques. A 4000 damping resistor is included on-chip in series with a Schottky diode pair to main-tain high input resistance in the read mode.

The VM31316 is available in a 52-lead PQFP. Please consult VTC for package availability.

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

VM31316

16-CHANNEL, HIGH-PERFORMANCE, THIN-FILM HEAD, READIWRITE PREAMPLIFIER

ABSOLUTE MAXIMUM RATINCS Power Supply Voltages:

August, 1994 Junction Temperature, ... 150°C Storage Temperature Range ... ... -65° to 150°C Thermal Characteristics, 9JA:

52-lead PQFP ... 70°CIW

RECOMMENDED OPERATINC CONDITIONS DC Power Supply Voltage:

Voo ... 12V ± 10%

Vee ... 5V± 10%

Junction Temperature ... O°C to 125°C

2-29

Dans le document Gain of ~ (Page 89-94)