LT5570
8
5570f
PIN FUNCTIONS
V
CC
(Pin 1): Power Supply Pin for the Bias Circuits. Typi-
cal current consumption is 26.5mA. This pin should be
externally bypassed with 1nF and 1μF chip capacitors.
IN
+
, IN
–
(Pins 2, 4): Differential Input Signal Pins. These
pins are preferably driven with a differential signal for
optimum performance. The pins are internally biased to
V
CC
– 1.224V and should be DC blocked externally. The
differential impedance is about 200Ω.
DEC (Pin 3): Input Common Mode Decoupling Pin. This
pin is internally biased to V
CC
– 1.224V. The input imped-
ance is about 1.75KΩ in parallel with a 10pF internal
shunt capacitor to ground. The impedance between DEC
and IN
+
(or IN
–
) is about 100Ω. The pin can be connected
to the center tap of an external balun. An ac-decoupling
capacitor may be connected to ground to maintain the IC
performance if necessary.
GND (Pin 5, Exposed Pad): Circuit Ground Return for
the Entire IC. This must be soldered to the printed circuit
board ground plane.
OUT (Pin 6): DC Output Pin. The output impedance is
mainly determined by an internal 100Ω series resistance
that provides output circuit protection if the output is
shorted to ground.
DNC (Pins 7, 8): Do Not Connect. Don’t connect any
external component at these pins. Avoid a long wire or
metal trace on the PCB.
EN (Pin 9): Enable Pin. An applied voltage above 2V will
activate the bias for the IC. For an applied voltage below
1V, the circuits will be shut down (disabled) with a corre-
sponding reduction in power supply current. If the enable
function is not required, then this pin should be con-
nected to V
CC
. Typical enable pin input current is 68μA for
EN = 5V. Note that at no time should the Enable pin voltage
be allowed to exceed V
CC
by more than 0.3V.
FLTR (Pin 10): Connection for an External Filtering Capaci-
tor C1. A minimum 22nF capacitor is required for stable
ac average power measurement. This capacitor should be
connected between Pin 10 and V
CC
.
