PT7M7433/34/35
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P
Supervisory Circuit
Features
User-Adjustable Low/High Thresholds with 615mV
Internal Reference
Low Current (1.5μA typ)
PT7M7427xx
PT7M7428xx
Single Low-Battery Outputs
LBO
Push-Pull LBO, Open-Drain LBO and
1
Open-Drain
LBO options
GND
90ms Minimum LBO Timeout Period
Immune to Short Battery Voltage Transients
2
BATT
Description
SOT23-3
-40° to + 85° Operating Temperature Range
C
C
SOT23-5
PT7M7430xx
PT7M7431xx
Application
Monitoring lithiumion (Li+) cells or multicell alkaline/
1 GND
LBOL
NiCd/ NiMH power supplies.
2
NC
The PT7M7433/34/35 are single-level battery monitors
with internal hysteresis. These devices are offered with
single low-battery output indicators which can be used
PT7M7429xx
to indicate three battery conditions: good (operate
1 LBO
system in normal mode), weak (operate system in low-
power mode), or empty (disable the system).
3
The PT7M7433/34/35 are
GND 3
user-adjustable threshold
voltages permitting the user to select the hysteresis
2 BATT
range and consequently the sensitivity of the system to
noise. A wide hysteresis range also prevents chattering
that can result due to battery recovery after load
PT7M7432xx
removal.
5
1
GND
LBOL
5
2
NC
3
LBOH
BATT
4
3
LBOH
BATT
4
Pin Configuration
PT7M7433
PT7M7434
1
HTHIN
VCC
5
1
PT7M7435
HTHIN
VCC
5
1
PT7M7479H
PT7M7479L
HTH
VDD
5
2
GND
2
GND
2
GND
RST
4
(/RST)
3
LTHIN
LBO
4
3
LTHIN
LBO
4
3
LTH
SOT23-6
Pin Description
Pin
1
2
3
4
5
Name
HTHIN
GND
LTHIN
LBO/LBO
VCC
1
PT7M7436
PT7M7437
PT7M7438
1 HTHIN VCC
Monitor Input.
A
PT7M3806M
PT7M3806E
Type
I
P
2
I
3
O
P
Description
6
1 RSTSENSE HSENSE 6
resistor-divider network sets the high
threshold associated with LBO/LBO.
GND
Ground
5
LBOH
2 GND
2 GND
LSENSE 5
LBOH 5
LTH Threshold Monitor Input.
A resistor-divider network sets the low
LBO/LBO.
LTHIN
threshold associated with
LTHIN LBOL 4
LBOL 4
3
3 RESET
VCC 4
Low-Battery Output.
LBO /LBO is asserted when LTHIN drops below V
LTHIN
,
and remains asserted for at least 90ms HTHIN rises above V
HTHIN
. Push-pull
output for PT7M7433. Open drain output for PT7M7434/35.
HTHIN
HTH Threshold
VCC 6
Supply Voltage.
Device power supply for adjustable threshold versions.
12-07-0002
1
PT0213-4
07/05/12
PT7M7433/34/35
P
Supervisory Circuit
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Block Diagram
PT7M7433/34/35Block Diagram
VCC
R1
LTHIN
R
HTHIN
S
R3
VCC
615
mV
LBO TIMOUT
PERIOD
Q
LBO
(LBO)
Q
VCC
R2
EXTERNAL
RESISTOR-
DRIVER
LBO: PT7M7433/34
LBO: PT7M7435
Maximum Ratings
Storage Temperature ............................................................-65
o
C to +150
o
C
Ambient Temperature with Power Applied.......................... -40
o
C to +85
o
C
Supply Voltage to Ground Potential (Vcc to GND) ..............-0.3V to +7.0V
DC Input Voltage (All inputs except Vcc and GND)......-0.3V to VCC+0.3V
DC Output Current (All outputs) ..........................................................20mA
Power Dissipation .............................................................................. 320mW
(Depend on package)
Note:
Stresses greater than those listed under MAXIMUM
RATINGS may cause permanent damage to the
device. This is a stress rating only and functional
operation of the device at these or any other condi-
tions above those indicated in the operational sec-
tions of this specification is not implied. Exposure
to absolute maximum rating conditions for extended
periods may affect reliability.
12-07-0002
2
PT0213-4
07/05/12
PT7M7433/34/35
P
Supervisory Circuit
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DC Electrical Characteristics
(V
CC
=1.8V to 5.5V, T
A
= -40~85º unless otherwise noted. Typical values are at T
A
= +25º
C,
C)
Description
Symbol
Test Conditions
Min
Operating Voltage Range
V
CC
I
CC
V
OH
T
A
= -40~85º
C
V
CC
= 3.7V, no load T
A
= -40~85º
C
V
CC
≥ 1.6V, I
source
= 200μA
Output High Voltage
(Push-Pull only)
V
CC
≥ 2.7V, I
source
= 500μA
V
CC
≥ 4.5V, I
source
= 800μA
V
CC
≥ 1.6V, I
sink
= 100μA
Output Low Voltage
Open-Drain Output
Leakage Current
Input Leakage Current
V
OL
V
CC
≥ 2.7V, I
sink
= 1.2mA
V
CC
≥ 4.5V, I
sink
= 3.2mA
I
LKG
I
LKG
-
V
HTHIN
or V
LTHIN
> 400mV
1.8
-
0.8×
Vcc
0.8×
Vcc
0.8×
Vcc
-
-
-
-
-
-1.5
-2.5
-1.5
-2.5
Typ
-
1.5
-
-
-
-
-
-
-
-
-
-
-
-
Max
5.5
2.5
-
-
-
0.3
0.3
0.4
1
20
+1.5
-2.5
+1.5
-2.5
μA
nA
%
%
%
%
V
V
Unit
V
μA
V
CC
Supply Current
User-adjustable Thresholds
(PT7M7433/34/35)
HTHIN rising, LBO is
T
A
= 25º
C
HTHIN Threshold(Note)
V
HTHIN
deasserted when HTHIN
T
A
= -30~70º
C
rises above 615mV.
LTHIN falling, LBO is
T
A
= 25º
C
LTHIN Threshold(Note)
V
LTHIN
asserted when LTHIN falls
T
A
= -30~70º
C
below 615mV.
Note:
Typical value is 615mV. Minimum and Maximum value is percentage of typical value.
AC Electrical Characteristics
Fig 1.
PT7M7433/34/35 timing diagram
V
HTH
V
CC
V
LTH
t
LBOP
LBO
(PT7M7433/34)
t
LBOD
t
LBOP
LBO
(PT7M7435)
t
LBOD
(V
CC
=1.8V to 5.5V, T
A
= -40~85º unless otherwise noted. Typical values are at T
A
= +25º
C,
C)
Symbol
t
LBOP
t
LBOD
Description
Timeout period
Delay
-
-
Test Conditions
Min
90
-
Typ
200
70
Max
350
-
Unit
ms
s
12-07-0002
3
PT0213-4
07/05/12
PT7M7433/34/35
P
Supervisory Circuit
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Function Description
The PT7M7433/34/35 are available with user adjustable monitoring.
The user sets the threshold voltages for the PT7M7433/34/35, which permit the user to select the hysteresis range, and
consequently the sensitivity of the system to noise. A wide hysteresis range prevents chattering that can result during battery
recovery or load removal. The PT7M7433/34/35 have single low-battery outputs.
The PT7M7433/34/35 combine a 615mV reference with two comparators, logic, and timing circuitry to provide the user with
information about the charge state of the power-supply batteries. The PT7M7433/34/35 monitor separate high-voltage and low-
voltage thresholds to determine battery status. The output can be used to signal when the battery is charged, when the battery is
low, and when the battery is empty. PT7M7433/34/35 are also available with thresholds determined using an external resistor-
divider (see Application information
Resistor-Value Selection).
The adjustable versions can monitor down to 0.62V, making them
suitable for monitoring single-cell alkaline, NiMH, and NiCd applications (V
CC
≥1.8V).
When the power-supply voltage drops below the specified low threshold, the low-battery output asserts (see
Low-Battery Output).
When the voltage rises above the specified high threshold following a 90ms (min) time-out period, the low-battery output is
deasserted (see
Threshold Monitoring).
This ensures the supply voltage has stabilized before power-converter or microprocessor
activity is enabled.
Low-Battery Output
The low-battery outputs are available in active-low (LBO, push-pull and open-drain) and action-high (LBO open-drain)
configurations. Push-pull outputs are referenced to V
CC
(for adjustable threshold versions).
The open-drain devices can be pulled to a voltage independent of V
CC
or BATT, up to 5.5V. This allows the device to monitor and
operate from direct battery voltage while interfacing to higher voltage microprocessors.
The PT7M7433/34/35 single-output voltage monitors provide a single low-battery output, LBO/LBO. The PT7M7433/34
adjustable-threshold parts assert LBO/LBO when the LTHIN input drops below the V
LTHIN
threshold (615mV).
Threshold Monitoring
The PT7M7433/34/35 HTHIN and LTHIN inputs are high-impedance inputs to comparators. An external resistor divider network
is required between the monitored voltage, HTHIN, LTHIN, and GND to select the desired thresholds (see Application
information
Resistor-Value Selection).
The PT7M7433/34/35 single-output voltage monitors assert LBO /LBO when LTHIN
drops below the internal LTHIN reference (615mV). LBO/LBO is deasserted when HTHIN rises above the internal HTHIN
reference level (615mV) for at least 90ms (see AC Electrical Characteristics: Fig 1).
Hysteresis
Hysteresis increases the comparator’s noise margin by increasing the upper threshold or decreasing the lower threshold (see blow).
The hysteresis prevents the output from oscillating (chattering) when V
CC
is near the low-battery threshold. This is especially
important for applications where the load on the battery creates significant fluctuations in battery voltages.
Adjustable Hysteresis (PT7M7433/34/35)
Block diagram shows the correct connections for the external resistor-dividers. To adjust the low-battery threshold and hysteresis
connect resistor R1 between V
CC
and LTHIN, resistor R2 between LTHIN and HTHIN, and R3 between HTHIN and GND. The
hysteresis for the PT7M7433/34/35 is determined by an external resistor-divider network (see Application information
Resistor-
Value Selection).
12-07-0002
4
PT0213-4
07/05/12
PT7M7433/34/35
P
Supervisory Circuit
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Fig 2.
PT7M7433/34/35 adjustable hysteresis
V
HTH
V
BATT
V
LTH
V
HYST
t
LBCP
LBO
HTH – Battery voltage good enable operation
LTH – Battery voltage low suspend/disable operation
Application Information
Resistor-Value Selection (Programming the Adjustable Thresholds)
V
REF
= V
LTHIN
= V
HTHIN
= 615mV
V
TRIPLOW
= V
LTH
= V
REF
( R1 + R2 + R3 )
R2 + R3
R1 + R2 + R3 )
V
TRIPHIGH
= V
HTL
= V
REF
(
R3
R
TOTAL
= R1 + R2 + R3
Use the following steps to determine values for R1, R2, and R3 of Functional Block Diagram.
1) Choose a value for R
TOTAL
. Because the PT7M7433/34/35 have very high input impedance, R
TOTAL
can be up to 5MΩ.
2) Calculate R3 based on R
TOTAL
and the desired upper trip point:
R3 =
V
REF
×
R
TOTAL
V
TRIPHIGH
615mV
×
R
TOTAL
V
TRIPLOW
=
615mV
×
R
TOTAL
V
TRIPHIGH
3) Calculate R2 based on R
TOTAL
, R3, and the desired lower trip point:
R2 =
- R3
4) Calculate R1 based on RTOTAL, R3, and R2:
R1 = R
TOTAL
– R2 – R3
12-07-0002
5
PT0213-4
07/05/12
嵌入式系统
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