LTC2934CDC1#PBF Linear Technology, LTC2934CDC1#PBF Datasheet - Page 8

• Manufacturer Part Number: LTC2934CDC1#PBF
• Manufacturer: Linear Technology

Specifications of LTC2934CDC1#PBF

• Voltage Supervisor Type: Voltage Monitor
• Number Of Voltage Supervisors: 1
• Reset Threshold Voltage (min): AdjV
• Reset Threshold Voltage (max): AdjV
• Operating Supply Voltage (min): 1.6V
• Operating Supply Voltage (max): 5.5V
• Operating Temperature Classification: Commercial
• Operating Temp Range: 0C to 70C
• Pin Count: 8
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

APPLICATIONS INFORMATION
LTC2934
R3 is easily obtained from:
The closest 1% value is 6.04M. Plugging the standard
values back into the equations yields the design values
for the falling power-fail and reset voltages:
Figure 2 demonstrates how the inputs can be biased
to monitor two voltages (V1, V2). In this example, four
resistors are required. Calculate each divider ratio for the
desired falling threshold (V
In Figure 2, PFO is tied back to the MR input, making the
state of the RST output dependent upon both V1 and V2. If
V1 and V2 are both above the confi gured falling threshold
plus hysteresis, RST is allowed to pull high. If independent
operation of the status outputs is desired, simply omit the
PFO to MR connection.
8
R3 = R
V
RnB
RnA
PF
V1
V2
= 1.720V, V
=
SUM
R2B
V
V
Figure 3. RST vs V
3.5
3.0
2.5
2.0
1.5
1.0
0.5
TH
FT
0
Figure 2. Dual Voltage Monitoring
– R1 – R2 = 8.1M – 1.87M – 130k = 6.1M
0
LTC2934-1
EXTERNALLY CONFIGURED
FOR 3V FALLING THRESHOLD
− =
1
R2A
0.5
R
R1B
= 1.608V
0 4
V
1
.
FT
V
R1A
1.5
FT
V
−
CC
CC
) using:
1
ADJ
PFI
(V)
with 10k Pull-Up
2
LTC2934
2.5
MR
RST
3
PFO
2934 F03
3.5
Selecting Output Logic Style
The LTC2934 status outputs are available in two options:
open-drain (LTC2934-1) or active pull-up (LTC2934-2).
The open-drain option (LTC2934-1) allows the outputs
to be pulled up to a user defi ned voltage with a resistor.
The open-drain pull-up voltage may be greater than V
(5.5V maximum), which is not always possible with
inferior battery supervisors, due to internal diode clamps.
When the status outputs are low, power is dissipated in
the pull-up resistors. Recommended resistor values lie in
the range between 10k and 470k. Figure 3 demonstrates
typical LTC2934-1 RST output behavior.
The active pull-up option (LTC2934-2) eliminates the
need for external pull-up resistors on the status outputs.
Integrated pull-up devices pull the outputs up to V
Actively pulled up outputs may not be driven above V
Some applications require the RST and/or PFO outputs to
be valid with V
this requirement with the addition of an external resistor
from the output to ground. The resistor provides a path
for leakage currents, preventing the output from fl oating to
undetermined voltages when connected to high impedance
(such as CMOS logic inputs). The resistor value should
be small enough to provide effective pull-down without
excessively loading the pull-up circuitry. A 100k resistor
from output to ground is satisfactory for most applications.
When the status outputs are high, power is dissipated in
the pull-down resistors. Figure 4 demonstrates typical
LTC2934-2 RST output behavior.
3.5
3.0
2.0
2.5
1.5
1.0
0.5
0
0
LTC2934-2
EXTERNALLY CONFIGURED
FOR 3V FALLING THRESHOLD
CC
0.5
down to ground. Active pull-up handles
Figure 4. RST vs V
1
1.5
V
CC
(V)
2
2.5
CC
3
2934 F04
3.5
2934f
CC
CC
CC
.
.