MAX UNITS (Note 1)

Differential Voltage Gain Av VIN =1mVrms, 1MHz, see Table 3 250 300 350 VN

-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 0.55 0.75 nV/-YHz

Differential Input Capacitance CIN VIN = 1mVp-p, 1 = 5MHz 14 18 pF

Differential Input Resistance RIN VIN = 1mVp-p, f = 5MHz 350 800 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 Vee 45 63 dB

Channel Separation CS Unselected channel driven with

45 55 dB

20mVp-p @ 5MHz

Output Offset Voltage Vos -250 ±10 250 mV

RDX, RDY Common Mode Output

VOeM Read Mode Vee -2.7 V

Voltage

Read to Write Common Mode

Ll.VoeM -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 mA

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

2-118 VTC Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425,612-853·5100

WRITE CHARACTERISTICS Recommended operating conditions apply unless otherwise specified,

4i

= 1 ~H, RH = 30n, Iw = 20mA, fDATA = 5MHz.

PARAMETER SYM CONomONS MIN TYP

MAX UNITS (Notfl1)

WC Pin Voltage Vwe 2.5 V

Iwe to Head Current Gain AI 20 mA/mA

Kw = (Vwe)(AI), 10 - 30mA 46 50 54

Write Current Constant Kw V

Kw = (Vwe)(AI), 5 - 35mA 45 50 55

Write Current Range Iw 1.258K < Rwe < 60n 5 35 mA

Iw= 10-30mA -8 +8

Write Current Tolerance ~Iw %

Iw=5-35mA -10 +10

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 Current IUH 0.15 1 mA(pk)

RDX, ROY Common Mode Output

VCM Vee - 2.7 V

Voltage

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

VM7152 (Two Channels), VM7154 and VM7158 (Four Channels) Write

PARAMETER SYM CONOmONS MIN TYP MAX UNITS

Write Current Matching Between

~Iw 5mA < Iw < 35mA 10 %

Channels

Duty Cycle (25mA/head) 20 %

VTe Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425, 612-853-5100 2-119

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

PARAMETER SYM CONDITIONS

R/W Read to Write Delay tRW R/Wt090% Iw

RiW

Write to Read Delay tWR R/W to 90% of 100mV, 10 MHz read signal envelope

WSER to Read Delay tSR R/W to 90% of 100mV, 10MHz read signal envelope

CS

Unseleclto Select Delay tlR CS to 90% Iw or 90% of 100mV, 10MHz read signal envelope CS Select to Unselect Delay tRI CS to 10% of Iw

HSO - HS2 any Head Delay tHS HSO - HS2to 90% of 100mV, 10MHz read signal envelope WUS Safe to Unsafe Delay t01

WUS Unsafe to Safe Delay t02

Head Current Propagation Delay t03 LH = 0, RH = 0, from 50% points Head Current Asymmetry ASYM 50% duty cycle on WDI,

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

Head Current Rise/Fall Time !,Itt

10% to 90% points, LH = 11lH, RH=30Q

Note 1: Typical values are given at Vee = 5V and TA

=

25°C.

HEAD CURRENT

WUS

Figure 1: Write Mode Timing Diagram

MIN TYP MAX

(Note 1)

0.04 0.3

0.4 1

0.4 1

0.15 0.6

0.05 0.6

0.03 0.6

0.6 2.1 3.6

1.0 30

0.04 0.5

1.9 5

12 16

UNITS

!lS

!lS

!lS

!lS

!lS

!lS Ils Ils ns ns

ns

2-120 VTC Inc., 2800 East Old Shakopee Road, Bloomington, MN 55425, 612-853-5100

FEATURES

• High Performance

- Read Gain

=

200 - 300 VN Typical -Input Noise 0.75 nV/-.!Hz Maximum

- Head Inductance Range

=

0.2 - 5 !!H (0.5 !!H Typical) - Write Current Range 5 - 35 rnA

- Input Capacitance

=

18pF Typical

• TLL Write Data Inputs

• Servo Write Two or Four Channels at the Same Time - VM7162 Two-Channel Servo Write

- VM7164 Four-Channel Servo Write

- VM7168 Two Banks of Four-Channel Servo Write

• Very Low Power Dissipation

=

3 mW Typical in Sleep Mode

• Power Up/Down Data Protect Circuitry

• Fast Write-to-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 2, 4 or 8-Channels DESCRIPTION

The VM7160 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 powered disk drives. The VM7160 provides a two or four channel servo write feature, enabling the user to write servo information directly through the preamp.

The VM7160 provides write current switching in the write mode and a low noise data path in the read mode for up to eight 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 VM7160 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

- - - - -.... -..

-VM7160

2, 4 OR a-CHANNEL, 5-VOL T, THIN-FILM HEAD, READ/WRITE PREAMPLIFIER WITH MUL TIPLE SERVO WRITE CAPABILITY

August,1994

,,~.

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

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