E4717DBG SEMTECH [Semtech Corporation], E4717DBG Datasheet - Page 9

• Manufacturer Part Number: E4717DBG
• Description: Quad Channel, Per Pin Precision Measurement Unit
• Manufacturer: SEMTECH [Semtech Corporation]

REXT Selection
The Edge4717D is designed such that the maximum
voltage drop across REXT (RA, RB, RC, or RD depending
on range selected using RS0 and RS1 inputs) is
Resistor values can be chosen to operate the PMU at any
current range up to
following equation:
Voltage Clamps/Over-Current Detection
The Edge4717D features four pairs of on-board clamps
(one pair per channel), which can be used to clamp the
voltage of pins connected to SRC_OUT and SNK_OUT
between limits set by the voltages applied to SRC_MON
and SNK_MON. SNK_MON is a high impedance input
that establishes the upper clamping limit, while SRC_MON
is a high impedance analog input that establishes the lower
clamping limit. In addition to voltage clamping functionality,
the clamp circuitry of the Edge4717D also features over-
current detection capability. Over-current detection is only
enabled when one of the voltage clamping thresholds is
exceeded (FORCE + V
V
condition is signaled via the OPEN-RLY pin. OPEN_RLY is
an open drain output pin that pulls down when an over-
current condition is detected. OPEN_RLY functionality is
depicted in Table 8.
TEST AND MEASUREMENT PRODUCTS
Circuit Description (continued)
diode
2005 Semtech Corp. / Rev. 5, 10/14/05
C
C
C
C
C
C
T
REXT[ ] =
O
O
O
O
O
O
E
M
M
M
S
M
M
M
< SRC_MON).
T
P
P
P
P
P
P
I _
I _
I _
C
I _
I _
I _
a
O
N
N
N
N
N
N
n
Table 7. Comparator Truth Table
N
>
<
<
d
>
<
>
D
I
V I
V I
V I
V I
V I
V I
I T
M
M
M
M
M
M
O
IMAX[A]
A
A
A
N
I
I
I
N
N
N
2 [V]
X
X
X
diode
50 mA in accordance with the
When enabled, an over-current
, IMAX
IMAX
IMAX
IMAX
D
> SNK_MON or FORCE –
U
N
T
0
1
1
A /
L
T
H
50 mA for Range D
2 mA for Range C
80 A for Range B
3.2 mA for Range A
D
U
N
T
1
0
1
A /
G
T
L
2V.
For applications that require the use of external resistors
that are much smaller in Ohmic value than those that are
outlined in Table 2, one will need to account for the
variation in switch resistance vs. common mode voltage
of the range selection switches (A-D in Figure 3) when
specifying the overall accuracy of the application.
Common Mode Error/Calibration
In order to attain a high degree of accuracy in a typical
ATE application, offset and gain errors are accounted for
through software calibration. When operating the
Edge4717D in the Measure Current (MI) or Force Current
(FI) modes, an additional source of error, common mode
error, should be accounted for. Common mode error is a
measure of how the common mode voltage, V
input of the current sense amplifier affects the forced or
measured current values (see Figure 2). Since this error
is created by internal resistors in the current sense
amplifier, it is very linear in nature.
Using the common mode error and common mode linearity
specifications, one can see that with a small number of
calibration steps (see Applications note PMU-A1), the
effect of this error can be significantly reduced.
Table 8. Over-Current Detection Circuit Functionality
9
S
S
S
S
N
N
R
R
K
K
C
C
_
_
_
_
C
O
O
O
O
(V
a l
U
U
U
U
m
T
T
T
T
diode
<
>
p
<
>
C
F
F
F
F
o
O
O
O
O
n
R
R
external clamp diode).
R
R
d
C
C
is the forward voltage of the
C
C
t i
E
E
E
E
o i
+
+
V –
V –
n
V
V
d
d
d
d
o i
o i
o i
o i
d
d
d
d
e
e
e
e
I
I
I
I
C
C
C
C
C
A L
A L
A L
A L
a l
M
M
M
M
C
m
P
P
P
P
r u
N
N
p
>
<
>
<
e r
A /
A /
D
t n
5
5
5
5
Edge4717D
o i
5
5
5
5
d
m
m
m
m
e
A
A
A
A
www.semtech.com
O
P
E
N
1
0
1
0
1
1
_
CM
R
Y L
, at the