GND
3
GND
3
2
BATT
2
BATT
PT7M7436/37/38
|
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SOT23-5
PT7M7430xx
PT7M7431xx
1
GND
LBOL
P
Supervisory Circuit
PT7M7432xx
Description
5
1
Features
User-Adjustable
Low/High
Thresholds
585mV/615mV Internal Reference
2 NC
Low Current (1.5μA typ)
Dual Low-Battery Outputs
3
LBOH
with
BATT
Push-Pull active low, Open-Drain active low and
Open-Drain active high output options
PT7M7433
90ms Minimum LBOA/LBOL Timeout Period
PT7M7434
Immune to Short Battery Voltage Transients
VCC
-40° to + 85° Operating Temperature Range
C
C
2
GND
1
HTHIN
5
The PT7M7436/37/38 are dual-level battery monitors
with internal hysteresis. These devices are offered with
2
NC
dual low-battery output indicators which can be used to
indicate three battery
3
conditions: good (operate system
4
LBOH BATT 4
in normal mode), weak (operate system in low-power
mode), or empty (disable the system).
GND
LBOL
5
Applications
1
5
PT7M7435
PT7M7479H
PT7M7479L
5
HTHIN
1
VCC
Monitoring lithiumion (Li
+
)
HTH
cells
VDD
multicell
or
alkaline/ NiCd/ NiMH power supplies.
GND
2
GND
RST
4
(/RST)
2
3
LTHIN
LBO
4
3
LTHIN
LBO
4
3
LTH
Pin Configuration
SOT23-6
PT7M7436
PT7M7437
1
HTHIN
VCC
6
1
PT7M7438
HTHIN
VCC
6
1
PT7M3806M
PT7M3806E
RSTSENSE HSENSE 6
2
GND
LBOH
5
2
GND
LBOH
5
2
GND
LSENSE
5
3
LTHIN
LBOL
4
3
LTHIN
LBOL
4
3
RESET
VCC
4
Pin Description
Pin
1
2
3
4
Name
HTHIN
GND
LTHIN
LBOL
/LBOL
LBOH
/LBOH
VCC
Type
I
P
I
O
Description
HTH Threshold Monitor Input.
A resistor-divider network sets the high threshold
associated with LBOH/LBOH.
Ground
LTH Threshold Monitor Input.
A resistor-divider network sets the low threshold
associated with LBOL/LBOL.
Low-Battery Output Low.
LBOL/LBOL is asserted when LTHIN drops below V
LTHIN-
.
It remains asserted for at least 90ms after LTHIN rises above V
LTHIN+
. Push-pull output
for PT7M7436, open-drain output for PT7M7437/38.
Low-Battery Output High.
LBOH/LBOH is asserted when HTHIN drops below
V
HTHIN
. It remains asserted for at least 90ms after HTHIN rises above V
HTHIN+
. Push-pull
output for PT7M7436, open-drain output for PT7M7437/38.
Supply Voltage.
Device power supply.
5
6
O
P
12-07-0002
1
PT0212-6
07/05/12
PT7M7436/37/38
P
Supervisory Circuit
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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.
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
Operating Voltage Range
Symbol
V
CC
I
CC
Test Conditions
T
A
= -40~85º
C
V
CC
= 3.7V, no load, T
A
= -40~85º
C
V
CC
≥ 1.6V, I
source
= 200μA
V
OH
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
Min
1.8
-
0.8×
Vcc
0.8×
Vcc
0.8×
Vcc
-
-
-
-
-
Typ
-
1.5
-
-
-
-
-
-
-
-
Max
5.5
2.5
-
-
-
0.3
0.3
0.4
1
20
μA
nA
V
V
Unit
V
μA
V
CC
Supply Current
Output High Voltage
(Push-Pull only)
User-adjustable Thresholds
(PT7M7436/37/38)
HTHIN+ Threshold
(Note
1)
V
HTHIN+
HTHIN rising, LBOH is
deasserted when HTHIN
rises above 615mV.
HTHIN falling, LBOH is
asserted when HTHIN
falls below V
HTHIN-
. V
REF
=
585mV
LTHIN rising, LBOL is
deasserted when LTHIN
rises above V
LTHIN+
. V
REF
= 615mV
LTHIN falling, LBOL is
asserted when LTHIN falls
below V
LTHIN-
. V
REF
=
585mV
T
A
= 25º
C
T
A
=
-10~85º
C
T
A
= 25º
C
T
A
=
-10~85º
C
T
A
= 25º
C
T
A
=
-10~85º
C
T
A
= 25º
C
T
A
=
-10~85º
C
-2
-
-2
-
-2
-
-2
-
-
100
-
100
-
100
-
100
+2
-
+2
-
+2
-
+2
-
%
ppm/º
C
%
ppm/º
C
%
ppm/º
C
%
ppm/º
C
HTHIN- Threshold (Note
2)
V
HTHIN-
LTHIN+ Threshold (Note
1)
V
LTHIN+
LTHIN- Threshold
(Note
2)
V
LTHIN-
Note 1:
Typical value is 615mV. Minimum and Maximum value is percentage of typical value.
Note 2:
Typical value is 585mV. Minimum and Maximum value is percentage of typical value.
12-07-0002
2
PT0212-6
07/05/12
PT7M7436/37/38
P
Supervisory Circuit
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AC Electrical Characteristics
Fig 1.
PT7M7436/37/38 timing diagram
V
CC
V
HTH+
V
HTH-
V
LTH+
V
LTH-
t
LBOP
LBOL
(PT7M7436/37)
t
LBOD
t
LBOP
LBOH
(PT7M7436/37)
t
LBOD
t
LBOP
LBOL
(PT7M7438)
t
LBOD
t
LBOP
LBOH
(PT7M7438)
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
100
Max
350
-
Unit
ms
s
12-07-0002
3
PT0212-6
07/05/12
PT7M7436/37/38
P
Supervisory Circuit
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Block Diagram
VCC
R1
LTHIN
VCC
R2
HTHIN
LBO
TIMOUT
PERIOD
LBOL
(LBOL)
LBOH
(LBOH)
HYSTERESIS SWITCH
R3
VCC
615
mV
HYSTERESIS SWITCH
LBOL/LBOH: PT7M7436/37
LBOL/LBOH: PT7M748
Function Description
The PT7M7436/37/38 are available with user adjustable
monitoring.
The PT7M7436/37/38 combine a 585/615mV reference with
two comparators, logic, and timing circuitry to provide the
user with information about the charge state of the power-
supply batteries. The PT7M7436/37/38 monitor separate high-
voltage and low-voltage thresholds to determine battery status.
The outputs can be used to signal when the battery is charged,
when the battery is low, and when the battery is empty.
PT7M7436/37/38 are also available with thresholds
determined using an external resistor-divider (see Application
information
Resistor-Value Selection).
They 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.
The open-drain devices can be pulled to a voltage independent
of V
CC
, up to 5.5V. This allows the device to monitor and
operate from direct battery voltage while interfacing to higher
voltage microprocessors.
The PT7M7436/37/38 dual-output voltage monitors provide
two low-battery outputs, LBOH/LBOH and LBOL/LBOL.
They will assert LBOH /LBOH when HTHIN drops below
V
HTHIN-
, and assert LBOL/LBOL when LTHIN drops below
V
LTHIN-
.
Threshold Monitoring
The PT7M7436/37/38 dual-output voltage monitors assert
LBOL/LBOL when LTHIN drops below the LTHIN-
threshold and deassert LBOL/LBOL when LTHIN rises above
the LTHIN+ threshold for at least 90ms. LBOH/LBOH is
asserted when HTHIN drops below the HTHIN- threshold and
is deasserted when HTHIN rises above the HTHIN+ threshold
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. 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. The
hysteresis for the PT7M7436/37/38 is the differences between
V
HTHIN-
and V
HTHIN+
(1.05) or V
LTHIN-
and V
LTHIN+
(1.05).
PT0212-6
4
07/05/12
Low-Battery Output
The low-battery outputs are available in active-low (LBOH,
LBOL push-pull and open drain) and active-high (LBOH,
LBOL open drain) configurations. Push-pull outputs are
referenced to V
CC
.
12-07-0002
PT7M7436/37/38
P
Supervisory Circuit
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Application Information
Resistor-Value Selection (Programming the Adjustable
Thresholds)
V
REF
= V
LTHIN-
= V
HTHIN-
= 585mV
V
TRIPLOW
= V
LTH-
= V
REF
( R1 + R2 + R3 )
R2 + R3
V
TRIPHIGH
= V
HTL-
= V
REF
( R1 + R2 + R3 )
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
, the sum of R1, R2, and R3.
Because the PT7M7436~PT7M7438 have very high input
impedances, 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
=
585mV
×
R
TOTAL
V
TRIPHIGH
3) Calculate R2 based on R
TOTAL
, R3, and the desired lower
trip point:
R2 =
585mV
×
R
TOTAL
V
TRPLOW
- R3
4) Calculate R1 based on RTOTAL, R3, and R2:
R1 = R
TOTAL
– R2 – R3
V
HTH+
= V
HTH-
×
1.05, V
LTH+
= V
LTH-
×
1.05
Mechanical Information
TAE (SOT23-6)
PKG. DIMENSIONS(MM)
SYMBOL
Min
Max
A
0.70
0.90
A1
0.00
0.10
A2
0.70
0.80
b
0.35
0.50
c
0.08
0.20
Note:
1) Controlling dimensions in millimeters.
D
E
E1
e
e1
L
θ
2.82
3.02
1.60
1.70
2.65
2.95
0.95 BSC
1.90 BSC
0.30
0.60
0°
8°
12-07-0002
5
PT0212-6
07/05/12
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