three main functions: pushbutton on/off control of system
power, ideal diode PowerPath controllers and system moni-
toring. The LTC2952’s pushbutton input, which provides
on/off control of system power, has independently adjust-
able ON and OFF debounce times. A simple microprocessor
interface involving an interrupt signal allows for proper
system housekeeping prior to power-down.
The ideal diode PowerPath controllers provide automatic
low loss switchover between two DC sources by regulating
two external P-channel MOSFETs to have a small 20mV
forward drop.
High reliability systems may utilize the LTC2952’s monitor-
ing features to ensure system integrity. These features in-
clude: power-fail, voltage monitoring and μP watchdog.
The LTC2952 operates over a wide operating voltage range
to accommodate a large variety of input power supplies. The
part’s combination of low 20mV external MOSFET regula-
tion and very low standby current matches battery powered
and power conscious application requirements.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
Pushbutton On/Off Control
Automatic Low Loss Switchover Between DC
Sources
Wide Operating Voltage Range: 2.7V to 28V
Low 25μA Shutdown Current
Guaranteed Threshold Accuracy: ±1.5% of
Monitored Voltage Over Temperature
Adjustable Pushbutton On/Off Timers
Simple Interface Allows Graceful μP Shutdown
Extendable Housekeeping Wait Time Prior to
Shutdown
200ms Reset Delay and 1.6s Watchdog Timeout
±8kV HBM ESD on
PB
Input
20-pin TSSOP and QFN (4mm
×
4mm) Packages
APPLICATIONS
n
n
n
n
n
Desktop and Notebook Computers
Portable Instrumentations
Cell Phones, PDA and Handheld Computers
Servers and Computer Peripherals
Battery Backup Systems
TYPICAL APPLICATION
Pushbutton Controller with Automatic Switchover Between Adapter and Battery
ADAPTER, 3V TO 25V
Si6993DQ
2.5V
V
IN
V
OUT
1k
365k
511k
G1
G2
V1
V2
LTC2952
VS
PFI
EN
VM
D1
RST
M1
M2
PB
ONT
*22nF
G1STAT
PFO
INT
KILL
GND OFFT WDE
*68nF
*OPTIONAL
2952 TA01
Ideal Diode vs Schottky Diode
Forward Voltage Drop
1
CONSTANT
R
ON
CURRENT (A)
LT1767-2.5
SHDN
Si6993DQ
100k
1k
1k
10k
12V BATTERY
D2
100k
D3
IDEAL
DIODE
CONSTANT
VOLTAGE
SCHOTTKY
DIODE
μP
0
0.02
FORWARD VOLTAGE (V)
0.50
2952 TA01b
2952fa
1
LTC2952
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Supply Voltages
V1, V2, VS.............................................. –0.3V to 30V
Input Voltages
PB
.................................... –6V to MAX (V1, V2, VS) V
ONT, OFFT ............................................... –0.3V to 3V
M1, M2, PFI, VM, WDE,
KILL
................... –0.3V to 7V
Output Voltages
G1, G2, EN .................... –0.3V to MAX (V1, V2, VS) V
G1STAT,
PFO, RST, INT
............................ –0.3V to 7V
Input Currents
PB
.......................................................–1mA to 100μA
Operating Temperature Range
LTC2952C ................................................ 0°C to 70°C
LTC2952I .............................................–40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
PIN CONFIGURATION
TOP VIEW
G1STAT
TOP VIEW
KILL
M1
M2
M1
KILL
VM
PFI
WDE
PB
RST
PFO
1
2
3
4
5
6
7
8
9
M2
20 G1STAT
19 G1
18 V1
17 VS
16 V2
15 G2
14 EN
13
INT
12 GND
11 OFFT
6
PFO
7
ONT
8
OFFT
9 10
GND
INT
VM 1
PFI 2
WDE 3
PB
4
RST
5
21
15 V1
14 VS
13 V2
12 G2
11 EN
G1
20 19 18 17 16
ONT 10
F PACKAGE
20-LEAD PLASTIC TSSOP
T
JMAX
= 125°C,
θ
JA
= 90°C/W
UF PACKAGE
20-LEAD (4mm 4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 37°C/W
EXPOSED PAD (PIN 21), PCB GND CONNECTION OPTIONAL
ORDER INFORMATION
LEAD FREE FINISH
LTC2952CF#PBF
LTC2952IF#PBF
LTC2952CUF#PBF
LTC2952IUF#PBF
TAPE AND REEL
LTC2952CF#TRPBF
LTC2952IF#TRPBF
LTC2952CUF#TRPBF
LTC2952IUF#TRPBF
PART MARKING
LTC2952CF
LTC2952IF
2952
2952
PACKAGE DESCRIPTION
20-Lead Plastic TSSOP
20-Lead Plastic TSSOP
20-Lead 4mm × 4mm Plastic QFN
20-Lead 4mm × 4mm Plastic QFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
2952fa
2
LTC2952
ELECTRICAL CHARACTERISTICS
SYMBOL
V
MAX
I
IN_OFF
PARAMETER
Operating Supply Voltage
Quiescent Supply Current Both Ideal
Diodes Switched Off
(M1 = Open, M2 = 0V)
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V1 = V2 = VS = 2.7V to 28V unless otherwise noted. (Notes 2, 3)
CONDITIONS
V1, V2 or VS
V1 = 2.7V to 28V, V2 = 0V, VS = Open or
V2 = 2.7V to 28V, V1 = 0V, VS = Open.
Measured Current at V1 or V2.
V1 = 2.7V to 28V, V2 = 3.5V, VS = Open.
Measured Current at V1.
V1 = 2.7V to 28V, V2 = 3.5V, VS = Open.
Measured Current at V2.
l
l
MIN
2.7
TYP
24
MAX
28
60
UNITS
V
μA
l
l
l
5
23
65
15
50
170
μA
μA
μA
I
IN_ON
Quiescent Supply Current Both Ideal
Diodes Switched On
(M1 = 0V, M2 = 0V)
V2 Preferential Threshold Voltage
(M1 = Open, M2 = 0V) (Note 4)
V1, V2 and VS Inter Pin Leakage to
the Highest Supply
Ideal Diode PowerPath Forward
Regulation Voltage
Ideal Diode PowerPath Fast Reverse
Turn-Off Threshold Voltage
Gate Turn-Off Current
Gate Turn-On Current
V1 = VS = 2.7V to 28V, V2 = 0V or
V2 = VS = 2.7V to 28V, V1 = 0V. Measured
Combined Current at V1 and VS or V2 and VS.
V1 = 28V, VS = Open.
V1 = 28V, V2 = VS = 0V; V1 = VS = 0V,
V2 = 28V; V1 = V2 = 0V, VS = 28V
(V1 or V2) – VS, 2.7V ≤ (V1 or V2) ≤ 28V
(V1 or V2) – VS, 2.7V ≤ (V1 or V2) ≤ 28V
ΔI
G
≤ –100μA/mV
G1 = G2 = V
MAX
– 1.5V
V1 = V2 = 2.7V to 28V,
VS = (V1 or V2) – 40mV,
G1 = G2 = V
MAX
–1.5V.
V1 = V2 = 2.7V to 28V,
VS = (V1 or V2) + 0.1V,
G1 = G2 = V
MAX
–1.5V.
V1 = V2 = 5V to 28V,
VS = (V1 or V2) – 0.1V,
G1 = G2 = V
MAX
– 1.5V.
I
GX
= 2μA, V
X
= 8V to 28V, VS = V
X
– 0.1V
Measure V
X
– V
GX
I
GX
= –2μA, V
X
= 2.7V to 28V, VS = V
X
+ 0.1V
Measure V
MAX
– V
GX
V
G(OFF)
to V
GS
≤ –3V, C
GATE
= 1nF (Note 5),
V1 = V2 = 12V
V
G(ON)
to V
GS
≥ –1.5V, C
GATE
= 1nF (Note 6),
V1 = V2 = 12V
I
PB
= –1μA
V
PB(VOC)
< V
PB
≤ 28V
0V ≤ V
PB
< V
PB(VOC)
PB
Falling From High to Low
V2
PREF_TH
I
LEAK
l
3.3
3.8
±3
V
μA
Ideal Diode Function
V
FR
V
RTO
I
G(SRC)
I
G(SNK)
l
l
l
l
10
–20
–2
2
20
–35
–5
5
35
–64
–10
10
mV
mV
μA
μA
I
G(FASTSRC)
Gate Fast Turn-Off Source Current
l
–0.5
–2.5
–10
mA
I
G(FASTSNK)
Gate Fast Turn-On Sink Current
l
0.3
0.7
2
mA
V
G(ON)
V
G(OFF)
t
G(ON)
t
G(OFF)
Gate Clamp Voltage
Gate Off Voltage
Gate Turn-On Time
Gate Turn-Off Time
l
l
6
7
0.2
8
0.4
10
10
V
V
μs
μs
0.1
0.1
2.5
2.5
Pushbutton Pin (PB)
V
PB(VOC)
I
PB
V
TH_PB
V
HYS_PB
PB
Open-Circuit Voltage
PB
Input Current
PB
Input Threshold Voltage
PB
Input Hysteresis
l
l
l
l
l
1
–1
0.65
10
4
–10
0.77
25
6
±1
–25
0.8
150
V
μA
μA
V
mV
2952fa
3
LTC2952
ELECTRICAL CHARACTERISTICS
SYMBOL
I
ONT,OFFT
t
DB,ON/OFF
PARAMETER
ONT/OFFT Pull-Up/Pull-Down Current
When Timer Is Active
Internal Default On-Time/Off-Time
Debounce Time Pins (ONT, OFFT)
V
ONT,
V
OFFT
= 0V (Pull-Up), V
ONT,
V
OFFT
= 1.5V
(Pull-Down)
t
DB,ON
: C
ONT
= Open, Measured Time Between
PB
Low
→
EN High, t
DB,OFF
: Measured Time
Between
PB
Low
→
INT High
C
ONT
= 1500pF C
OFFT
= 1500pF
,
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V1 = V2 = VS = 2.7V TO 28V unless otherwise noted. (Notes 2, 3)
CONDITIONS
MIN
±1.6
18
TYP
±2.0
26
MAX
±2.4
34
UNITS
μA
ms
t
ONT,OFFT
Additional Adjustable Turn-On/Turn-
Off Time (Note 7)
VM Input Reset Threshold
PFI, M1, M2,
KILL
Input Threshold
Voltage
PFI, M1, M2,
KILL
Input Hysteresis
VM, PFI, M2,
KILL
Input Current
M1 Input Pull-Up Current
M1 Voltage Open-Circuit
M1 Input Leak Current
Input High Threshold Voltage
Input Low Threshold Voltage
High Low Input Current (Note 8)
Hi-Z Input Current
Leakage Current
Voltage Output Low
EN Leakage Current
EN Voltage Output Low
l
10
15
20
ms
Accurate Comparator Input Pins (VM, PFI, M1, M2,
KILL)
V
TH_VM
V
TH
V
HYS
I
IN_LKG
I
M1_SRC
V
M1(VOC)
I
M1_LKG
V
WDE(H,TH)
V
WDE(L,TH)
I
WDE(IN,HL)
I
WDE(IN,HZ)
I
OUT_LKG
V
OL
I
EN(LKG)
V
EN(VOL)
Both Falling and Rising
Falling
l
l
l
0.492
0.492
5
–1.5
1
0.500
0.500
15
–3
4
0.508
0.508
25
±0.1
–5
6
±0.1
1.5
V
V
mV
μA
μA
V
μA
V
V
μA
μA
V = 0.5V
M1 = 1V
M1 = 6V
l
l
l
l
l
l
l
Watchdog/Extend Pin (WDE)
0.3
±25
±10
±1
0.4
±1
0.4
0.05
140
1.1
200
1.6
5
150
150
0.3
260
2.1
10
V
WDE
= 0.7V, 1.1V
V
PIN
= 5V
I
PIN
= 1mA
V
EN
= 28V, EN Sink Current Off
I
EN
= 3mA
V1 = 1.2V and/or V2 = 1.2V, I
EN
= 100μA
l
l
l
l
l
l
l
l
l
Open-Drain Output Pins (G1STAT,
INT, RST, PFO)
μA
V
μA
V
V
ms
s
μs
μs
μs
High Voltage Open-Drain Output Pin (EN)
Voltage Monitor/Watchdog Timing
t
RST
t
WDE
t
WDE(PW MIN)
t
VM(UV)
t
PFI
Reset Timeout Period
Watchdog Timeout Period
Minimum Period Between
Consecutive Edges
VM Undervoltage Detect to
RST
PFI Delay to
PFO
VM Less Than V
TH_VM
by More Than 1%
PFI More or Less Than V
PFI_TH
by More
Than 1%
2952fa
4
LTC2952
ELECTRICAL CHARACTERISTICS
SYMBOL
t
INT(MIN)
t
KILL(PW)
t
KILL,ON
BLANK
t
KILL,
OFF WAIT
t
EN, LOCKOUT
PARAMETER
INT
Minimum Pulse Width
KILL
Minimum Pulse Width
KILL
On Blanking (Note 9)
KILL
Wait Time (Note 10)
Enable Lockout Time (Note 11)
μP Handshake Timing
Minimum Measured Time
PB
Rising to
INT
Rising
Full Swing Pulse From 5V to 0V
KILL
= 0V, Measured Time Between EN Rising
→
EN Falling
KILL
= 1V, C
OFFT = OPEN
, Measured Time
Between
INT
Falling
→
EN Falling
Measured Time Between EN Falling
→
EN
Rising
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V1 = V2 = VS = 2.7V to 28V unless otherwise noted. (Notes 2, 3)
CONDITIONS
MIN
10
TYP
50
150
270
270
270
400
400
400
MAX
250
500
530
530
530
UNITS
μs
μs
ms
ms
ms
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The greatest of V1, V2 or VS is the internal supply voltage (V
MAX
).
Note 3:
All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 4:
V2
PREF_TH
is the minimum voltage level at which V2 becomes
the preferential source of quiescent current when both of the ideal diodes
are off.
Note 5:
VS is stepped from (V1 or V2) + 0.2V to (V1 or V2) – 0.2V to
trigger the event. The gate voltages are initially V
G(OFF)
.
Note 6:
VS is stepped from V
X
– 0.2V to V
X
+ 0.2V to trigger the event.
Gate voltages are initially clamped at V
G(ON)
.
Note 7:
The adjustable turn-on and turn-off timer period is the adjustable
debounce period following the Internal default-on and default-off timer
period, respectively.
Note 8:
The input current to the three-state WDE pin are the pull-up
and the pull-down current when the pin is either set to 3.3V or GND,
respectively. In the open state, the maximum pull-up or pull-down leakage
current permissible is 10μA.
Note 9:
The turn-on
KILL
blanking time is the waiting period immediately
following the EN pin switching high; at the end of this period the input
to the
KILL
needs to be high to indicate that the system has powered up
properly, otherwise the EN pin is immediately switched low.
Note 10:
The
KILL
wait time during the power-down process is the wait
period immediately following a valid turn-off command until the EN pin
switches low.
Note 11:
The enable lockout time is the minimum wait time between the
last falling edge and the next rising edge on the EN pin.
1. Introduction
Electronic scales are gradually replacing traditional measuring tools like springs and balances in everyday life, such as electronic price computing scales and electronic weigh...[详细]
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