IR2177STRPBF International Rectifier, IR2177STRPBF Datasheet - Page 11

• Manufacturer Part Number: IR2177STRPBF
• Description: IC CURRENT SENSE 0.2% 16SOIC
• Manufacturer: International Rectifier

Specifications of IR2177STRPBF

• Function: Current Sense
• Accuracy: ±0.2%
• Voltage - Input: 8 ~ 20 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Sensing Method: -

1
1.1 SYNC input
Sync input clocks the whole device. In order to
make the device work properly it must be
synchronous with the triangular PWM carrier as
shown in Figure 8.
SYNC pin is internally pulled-down (10 kΩ) to V
1.2 PWM Output (PO)
PWM output is an open collector output (active low).
It must be pulled-up to proper supply with an
external resistor (suggested value between 500Ω
and 10kΩ).
PO pull-up resistor determines the rising slope of
the PO output and the lower value of PO as shown
in Figure 7, where
capacitance and R is the pull-up resistance.
where R
and R
PO duty cycle is defined for active low logic by the
following formula:
Eq. 1
PO duty cycle (D
Zero input voltage corresponds to 20% duty cycle.
11
V
low
=
Figure 7: PO rising and falling slopes
pull-up
Supply
Supply
V
Device Description
D
on
low
n
is the external pull-up resistance.
is the internal open collector resistance
=
T
⋅
off
R
T
n
on
_
) swings between 10% and 30%.
cycle
τ
cycle
+
=
R
R
_
on
_
RC
n
pull
n
τ
+
1
−
, C is the total PO pin
up
SS
.
A residual offset can be read in PO duty cycle
according
characteristics).
According to
Figure 8, it can be assumed that odd cycles are
represented by SYNC at high level (let’s name
channel 1 the output related to this state of SYNC)
and even cycles represented by SYNC at low level
(channel 2).
The two channels are independent in order to
provide the correct duty cycle value of PO even for
non-50% duty cycle of SYNC signal. Small variation
of SYNC duty cycle are then allowed and
automatically corrected when calculating the duty
cycle using Eq. 1.
However, channel 1 and channel 2 can have a
difference in offset value which is specified in
To implement a correct offset compensation of PO
duty cycle and analog OUT, each channel must be
compensated separately.
1.3 Over Current output (OC)
OC output is an open drain pin (active low).
A simplified block diagram of the over current circuit
is shown in the
Figure 9.
Over current is detected when |V
If an event of over current lasts longer than t
OC pin is forced to V
PO is externally forced low for at least t
timing on Figure 4). During an over current event
(OC is low), PO is off (pulled-up by external
resistor).
If OC is reset by PO and over current is still active,
OC pin will be forced low again by the next edge of
SYNC signal.
To reset OC state PO must be forced to V
least T
•
The autoreset function consists in clearing
automatically the OC fault.
To enable the autoreset function, simply short
circuit the OC pin with the PO pin.
∆V
POS
Autoreset function
OCoff
(see Static electrical characteristics).
.
to
IR2277S/IR2177S(PbF)
V
POs
SS
and remains latched until
(see
in
|=|V
Static
inp
www.irf.com
-V
inm
OCoff
electrical
SS
|>V
for at
dOCon
(see
OCth
.
,