RECOMMENDED OPERATINC CONDITIONS DC Power Supply Voltage:

Voo ... 12V ± 10%

Vee ... 5V± 10%

Junction Temperature ... O°C to 125°C

2-29

~,~,~ VM31316 ~~.

_~~,

The VM31316 addresses 16 two-tenninal thin film heads, pro-viding write drive or read amplification. Head selection and mode control are accomplished with pins HSn,

CS

and Rm,

as

shown in Tables 1 and 2. Internal resistor pullups provided on pins

CS

and

Rfiiii

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

Write Mode

Write mode configures the VM31316

as

a current switch and activates the write unsafe (WUS) detection circuitry. Write cur-rent is toggled between the X and Y direction of the selected head on each high-to-Iow transition on pins WDI -

WDT

(differen-tial PECl 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 extemal resistor connected between the WC pin and ground. An inter-nally generated 1.71V reference voltage is present at the WC pin. The magnitude of the write current (O-pk,

±

8%) is:

Iw= 1.65

VI Rwe

2-30

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 VM31316 because the inter-nal 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 as a high level on the open collector output pin, WUS. Two negative transitions on pin WDI, after the fault is corrected, may be required to clear the WUS flag.

Read mode configures the VM31316 as a low-noise differen-tial amplifier and deactivates the write current generator and write unsafe detection circuitry. The RDX and RDY outputs are emitter followers and are in phase with the "X" and "Vi. head ports. These outputs should be AC coupled to the load. The RDX, ROY 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 sub-sequent Pulse Detection circuitry. Multiple devices may have there read outputs wire OR'ed together.

Idle Mode

When

cg

is high, virtually the entire circuit is shut down so that power dissipation is reduced to less than 180 mW for a sleep mode ..

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

Table 2: Head Select TYPICAL APPLICATION

HSO HS1 HS2 HS3 HEAD ^{+5V +12V}

0 0 0 0 0

1 0 0 0 1

0 1 0 0 2

O.Q1~F

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

RDX

^{M,,' 0_}

~-RDY

1Iill lkn

0 0 0 1 8

VM31316

1 0 0 1 9 ^Wl'5l PECl level'

WDI

0 1 0 1 10

1 1 0 1 11

0 0 1 1 12

1 0 1 1 13

CS

}m~'

RfW HSO HSI HS2 HS3

0 1 1 1 14

1 1 1 1 15

PIN DESCRIPTIONS GND

NAME VO DESCRIPTION

HSO - HS3 I' Head Select: selects one of up to 16 heads

HOX- H15X

I/O X, Y Head Terminals HOY - H15Y

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

current.

CS

I Chip select: low level enables the device

ReadIWrite 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

WC Write Current: a resistor adjusts level of write current

RDX,RDY

0'

Read Data Output: differential output data

VCC +5 volt logic circuit supply

VDD +12 volt supply

GND Ground

, When more than one RIW device is used, these signals can be wire OR'ed.

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

, For proper operation in read or write mode the WDIIWDI inputs must be correctly biased to their respective PECl levels.

They cannot float of both be tied high or low.

2-31

~~.J .~. ^VM31316

DC CHARACTERISTICS Unless otherwise specified, recommended operating conditions apply.

PARAMETER SYM CONDmONS 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+lw mA

Idle Mode 15

Read Mode 500 670

Power Dissipation (T J = 125^DC) Po Write Mode: Iw=20mA \ 625 BOO mW

Idle Mode 105 1BO

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

IJA

WDI,

Wl>T

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

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

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

IJA

WDI,

Wl>T

Input Low Current IlL VIL = Vee -1.6V BO

IJA

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 S 3.5V,

-200 +200

0< VOO< 9V

Head Current (HnX, HnY) IH

IJA

Write Mode, 0 < Vee < 5.5V,

-200 +200

0< Voo < 13.2V

2-32 VTC Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425, 612-853-5100

VM31316 ~!~

~~#

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 nV/¥Z

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 < T A < 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 VCM = 100mVp-p @5MHz 54 dB

Power Supply Rejection Ratio PSRR 100mVp-p @5MHzon

54 dB

VooorVcc

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 Vcc- 2.S Vcc - 2.3 Vcc- 2.O

Voltage VOCM V

Write Mode Vcc- 2.S Vcc - 2.3 Vcc- 2.O

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

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

WRITE CHARACTERISTICS Unless otherwise specified, recommended operating conditions apply, Iw = 20mA, LH = 1.0I1H, RH = 300 and fOATA = 5MHz.

PARAMETER SYM CONDITIONS MIN TYP MAX UNITS

WC Pin Voltage Vwc 1.65 V

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

Unselected Head Current IUH 1.0 mA (pk)

Differential Output Capacitance COUT 25 pF

Differential Output Resistance ROUT 3.2 kO

WDI Transition Frequency. 'OATA WUS = low 1.7 MHz

Write Current Range Iw 41.250< Rwc < 1650 10 40 mA

Write Current Tolerance dlw Iw range 10mA to 40mA -S +S %

VTC Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425, 6t2-853-5100 2-33

~~+J ~~. ^VM31316

SWITCHING CHARACTERISTICS (see Figura 1) Unless otherwise specified, recommended operating conditions apply, Iw = 20mA, LH = 1.01lH, RH = 300 and fOATA = 5MHz.

PARAMETER

RIViI

to Write Mode

RIViI

to Read Mode

CStoSelect

cs

to Unselect

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

Rise/Fall Time

Rise/Fall Time

WUS

HEAD CURRENT(lw}

SYM

tRW

tWR

tlR

tlW tHS t01 t02 t03 ASYM

tA

tA

Figure 1: Write Mode Timing Diagram

CONDmONS 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% WOI to 50% WUS 0.6 3.6

50% WOI to 50% WUS 1

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

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

10% - 90% points, Iw = 20mA, LH = 600nH, RH = 200 9

UNITS

I1S I1S

I1S I1S I1S I1S I1S ns ns

ns

ns

2-34 VTC Inc., 2800 East Old Shakopee Road, Bloomlilgton, MN 55425, 612-853-5100

~.~:.~ ~,

_~~.~~

^{VTC Inc.}

Value the CustomerTM

FEATURES

• High Performance:

- Read Mode Gain

=

^250VN

- low Input Noise

=

0.8nV/'-'Hz Maximum - Input Capacitance

=

25pF Maximum - Write Current Range

=

1 OmA to 40mA - Head Inductance Range

=

^{200nH to 3~H}

- Head Voltage Swing

=

7Vp-p Minimum - Write Current Rise Time

=

5ns

• 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 Pseudo ECl Write Data Input DESCRIPTION

The VM313H is a high-performance,low-power, high gain, bipolar monolithic read / write preamplifier designed for use with two-terminal thin-film recording heads. It provides write current control, data protection circuitry and a low-noise read preampli-fier for fourteen channels. When unselected, the device enters a sleep mode, with power dissipation reduced to less than 180mW. Fault protection is provided so that during power sup-ply sequencing the write current generator is disabled. System write-to-read recovery lime is minimized by maintaining the read channel common-mode output voltage in the write mode. The VM313H features a read mode voltage gain of 250VN.

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 VM313H is available in a variety of package

configura-·tions. Please consult VTC for package availability.

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

VM313H

14-CHANNEL, HIGH-PERFORMANCE,

Dans le document Gain of ~ (Page 94-100)