3

SL1710

ELECTRICAL CHARACTERISTICS (continued)

Tamb= 0

o

C to 80

o

C, Vee= 0V, Vcc = 4.75 to 5.25 V, These characteristics are guaranteed by either production test or design.

They apply within the specified ambient temperature and supply voltage unless otherwise stated.

Value

Characteristic

Pin

Min

Typ

Max

Units

Conditions

Prescaler sidebands

2, 7

-50

-47

dBV

Measured in IQ outputs

Power supply rejection

2, 7

25

30

dB

Attenuation VCC to IQ outputs,

over 0-500kHz

Notes:

1. The choice of L will have an effect on phase noise of the VCO

2. Target value at fo=500MHz, L (tank)=10nH, Q (tank, unloaded)=50, SSB

DESCRIPTION

The SL1710 is a quadrature downconverter, intended for

high linearity, low noise digital satellite applications. It contains

all the elements necessary, with the exception of the VCO

tuning components, to extract baseband I and Q signals from

a QPSK or QAM IF input signal.

A block diagram for the SL1710 is shown in Fig. 2.

In normal consumer digital satellite applications, the device

is fed via a SAW filter, centred at the standard IF of 479.5MHz.

A filtered single channel is therefore presented to the device,

at a typical level of -51dBV. An AGC is included with 18dB of

gain control, which is guaranteed to provide an overall conver-

sion gain between 30 and 45dB from the RF input to the I and

Q outputs.

The quadrature mixers are fed from an on-chip oscillator

which is centred on the incoming IF. The oscillator external

tuning network should be fully symmetric, to ensure optimum

gain and phase match.

Single ended I and Q amplifiers are provided, which output

a 760mV (p/p) signal, assuming a nominal -51dBV input signal

and 40dB gain, suitable for driving a dual channel ADC such as

the PCA 869, PCA 913 and PCA 916 via an anti-alias filter (see

application notes). The ADC is normally AC coupled via two

capacitors (typically 4.7

µF).

The SL1710 also includes divide by 32 prescaler output.

These may be fed to an external PLL circuit which can be used

to drive the on-chip oscillator, thus forming a complete control

loop.

The VCO can be disabled by applying 0V to pin 15.