LTC1981/LTC1982
1
APPLICATIO S
U
DESCRIPTIO
U
FEATURES
The LTC
®
1981/LTC1982 are low-power, self-contained
N-channel MOSFET drivers. An internal voltage tripler
allows gates to be driven without the use of any external
components. Internal regulation circuitry allows quies-
cent current to drop to 10µA per driver (20µA for LTC1981)
once the gates are charged.
Low quiescent current and low shutdown current (under
1µA) make these parts ideal for battery and other power
constrained systems. The wide input voltage range ac-
commodates a variety of battery/input configurations.
Gate drive is internally clamped to 7.5V providing protec-
tion to the external MOSFET gate. The MOSFETs can be
driven in either high side or low side mode.
The LTC1981 single driver version also includes a gate
drive ready pin and twice the drive current capacity of the
dual driver LTC1982.
The LTC1981 is available in a 5-pin SOT-23. The LTC1982
is available in a 6-pin SOT-23.
■
Cellular Telephones
■
Portable POS Terminal
■
Handheld Battery Powered Equipment
, LTC and LT are registered trademarks of Linear Technology Corporation.
■
No External Components Required
■
Internal Voltage Triplers Produce High Side
Gate Drive for Logic Level FETs
■
Ultralow Power:
10µA Per Driver ON Current (LTC1982)
20µA ON Current (LTC1981)
<1µA Shutdown Current
■
V
CC
Range: 1.8V to 5V
■
Gate Drive Outputs Driven to Ground During
Shutdown
■
Gate Drive Outputs Internally Clamped to 7.5V Max
■
“Gate Drive Ready” Output (LTC1981)
■
Ultrasmall Application Circuit
■
5-Pin SOT-23 Package (LTC1981)
■
6-Pin SOT-23 Package (LTC1982)
Single and Dual Micropower
High Side Switch Controllers
in SOT-23
VCC GATE
SHDNGNDGDR
LTC1981 LOAD
+
10µF
GATE
DRIVE
READY
SHDN
VCC
1.8V TO 5.0V
54
123
1981/82 TA01
100k
Q1
Si3442DV
V
CC
GATE 1 GATE 2
SHDN 1 SHDN 2GND
LTC1982 LOAD 1 LOAD 2
+
10µF
SHDN 1
SHDN 2
V
CC
1.8V TO 5.0V
654
123
1981/82 TA02
Q1
1/2 Si6925DQ
Q2
1/2 Si6925DQ
TYPICAL APPLICATIONS
U
Single High Side Switch Controller Dual High Side Switch Controller
LTC1981/LTC1982
2
Terminal Voltage
LTC1981: V
CC
, GATE, SHDN, GDR ........ –0.3V to 7.5V
LTC1982: V
CC
, GATE 1, GATE 2,
SHDN 1, SHDN 2 ................... –0.3V to 7.5V
ABSOLUTE AXI U RATI GS
W
WW
U
(Notes 1, 2)
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise specified. CGATE 1 = CGATE 2 = CGATE = 1000pF.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
CC
Operating Supply Voltage ●1.8 5.5 V
I
CC
Supply Current GATE 1 and GATE 2 Outputs High ●17 30 µA
GATE 1 or GATE 2 Outputs High ●10 20 µA
GATE Output High (LTC1981) ●17 30 µA
I
SHDN
SHDN Supply Current SHDN 1 and SHDN 2 Inputs Low ●1µA
SHDN Input Low (LTC1981) ●1µA
V
GATE
GATE Drive Output Voltage V
CC
= 1.8V ●4.27 4.50 4.75 V
V
CC
= 2.7V ●6.40 6.75 7.10 V
V
CC
= 3.3V ●6.90 7.25 7.50 V
V
CC
= 5V ●6.90 7.25 7.50 V
f
OSC
Charge Pump Oscillator Frequency Measured with 10k Resistor from Output to GND 600 kHz
t
ON
Turn-on Time into 1000pF From SHDN 1, SHDN 2 Going High to
GATE 1, GATE 2 = V
CC
+ 1V 110 µs
From SHDN Going High to GATE = V
CC
+1V (LTC1981) 85 µs
t
OFF
Turn-off Time into 1000pF From SHDN 1, SHDN 2 Going Low to
GATE 1, GATE 2
,
GATE = 100mV 12 µs
V
IL
SHDN Input Low Voltage V
CC
= 1.8V to 5.5V ●0.4 V
V
IH
SHDN Input High Voltage V
CC
= 1.8V to 5.5V ●1.6 V
C
IN
SHDN Input Capacitance (Note 4) 5 pF
I
IN
SHDN Input Leakage Current ±1µA
ORDER PART
NUMBER
S6 PART
MARKING
T
JMAX
= 150°C, θ
JA
= 230°C/W
Consult factory for parts specified with wider operating temperature ranges.
LTPF
LTC1982ES6
PACKAGE/ORDER I FOR ATIO
UUW
Operating Temperature Range
LTC1981E/LTC1982E (Note 3) ............ –40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)..................300°C
ORDER PART
NUMBER
S5 PART
MARKING
T
JMAX
= 150°C, θ
JA
= 250°C/W LTSF
LTC1981ES5
4 GATE
5 VCC
SHDN 3
GDR 1
TOP VIEW
S5 PACKAGE
5-LEAD PLASTIC SOT-23
GND 2
SHDN 1 1
GND 2
SHDN 2 3
6 V
CC
5 GATE 1
4 GATE 2
TOP VIEW
S6 PACKAGE
6-LEAD PLASTIC SOT-23
LTC1981/LTC1982
3
SUPPLY VOLTAGE, V
CC
(V)
1.5
GATE DRIVE VOLTAGE (V)
5.5
1982 G01
2.5 3.5 4.5 5.0
2.0 3.0 4.0
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
T
A
= 25°C
GATE DRIVE VOLTAGE
(V
GS
COMMON SOURCE)
GATE DRIVE –V
CC
(V
GS
SOURCE FOLLOWER)
SUPPLY VOLTAGE (V)
1.0
0
SUPPLY CURRENT (µA)
5
15
20
25
2.0 3.0 3.5 5.5
1982 G02
10
1.5 2.5 4.0 4.5 5.0
T
A
= 25°C
LTC1981 OR
BOTH CHANNELS ON
LTC1982
EITHER CHANNEL ON
LTC1982
GATE DRIVE VOLTAGE (V)
0
GATE DRIVE CURRENT (µA)
100
10
1
0.1 34 6712 5 8
1982 G03
V
CC
= 3.3V
V
CC
= 2.7V
V
CC
= 1.8V
T
A
= 25°C
V
CC
= 5V
SHDN LOGIC INPUT VOLTAGE (V)
01
SUPPLY CURRENT (µA)
60
50
40
30
20
10
0
1981/82 G04
2
T
A
= 25°C
V
CC
= 3V
SHDN1 TIED
TO SHDN2
SHDN LOGIC INPUT VOLTAGE (V)
01
SUPPLY CURRENT (µA)
300
250
200
150
100
50
0
1981/82 G05
2
TA = 25°C
VCC = 5V
SHDN1 TIED
TO SHDN2
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
OL
GDR Output Voltage Low I
SINK
= 100µA, V
CC
= 1.8V ●0.05 0.4 V
GATE Drive Ready Trip Point GATE Voltage Rising
V
CC
= 1.8V ●3.85 4.05 4.25 V
V
CC
= 2.7V ●5.78 6.08 6.38 V
V
CC
= 3.3V ●6.17 6.5 6.82 V
V
CC
= 5V ●6.17 6.5 6.82 V
GDR Hysteresis GATE Voltage Falling 2 %
GDR Delay After GATE is Above the GDR Trip Threshold 2 µs
10k Pull-Up to V
CC
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: All voltage values are with respect to GND.
Note 3: the LTC1982E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 4: Guaranteed by design not subject to test.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise specified. CGATE 1 = CGATE 2 = CGATE = 1000pF.
(LTC1981 only)
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Supply Current vs Supply Voltage
GATE Drive Voltage vs Supply
Voltage GATE Drive Current (LTC1982)
ISUPPLY ISUPPLY
LTC1981/LTC1982
4
TYPICAL PERFOR A CE CHARACTERISTICS
UW
SUPPLY VOLTAGE (V)
2.0
TURN-ON TIME (µs)
1982 G06
1.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
400
350
300
250
200
150
100
50
0
C
GATE
= 1000pF
T
A
= 25°C
V
GS
= 2V
V
GS
= 1V
SUPPLY VOLTAGE (V)
2.0
TURN-OFF TIME (µs)
1982 G07
1.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
40
35
30
25
20
15
10
5
0
C
GATE
= 1000pF
T
A
= 25°C
TIME FOR V
GATE
< 0.1V
TEMPERATURE (°C)
–60
GATE DRIVE VOLTAGE (V)
7.50
7.45
7.40
7.35
7.30
7.25
7.20
7.15
7.10
7.05
7.00 –20 20 40
1982 G08
–40 0 60 80 100
V
CC
= 3.3V
Turn-Off Time (LTC1982)Turn-On Time (LTC1982) GATE Drive Voltage vs
Temperature
Turn-On Time (LTC1981)GATE Drive Current (LTC1981) Turn-Off Time (LTC1981)
GATE DRIVE VOLTAGE (V)
01
100
10
1
0.1 2345678
GATE DRIVE CURRENT (µA)
1981/82 G09
V
CC
= 2.7V
V
CC
= 1.8V V
CC
= 5V
V
CC
= 3.3V
SUPPLY VOLTAGE (V)
1.5
TURN-ON TIME (µs)
2.5 3.5 4.0 6.0
1981/82 G10
2.0 3.0 4.5 5.0 5.5
300
250
200
150
100
50
0
C
GATE
= 1000pF
T
A
= 25°C
V
GS
= 2V
V
GS
= 1V
SUPPLY VOLTAGE (V)
1.5
0
TURN-OFF TIME (µs)
5
15
20
25
2.5 3.5 4.0 6.0
1981/82 G11
10
2.0 3.0 4.5 5.0 5.5
C
GATE
=1000pF
T
A
= 25°C
TIME FOR V
GATE
< 0.1
PIN FUNCTIONS
UUU
LTC1981:
GDR (Pin 1): Gate Drive Ready Active High Open Drain
Output. Used to indicate when the gate drive output is
greater than 90% of its final value.
GND (Pin 2): Ground.
SHDN (Pin 3): SHDN Active Low Input. Used to shut down
the part and force the GATE output pin to ground.
GATE (Pin 4): Gate Drive Output to an External High Side
Switch. Fully enhanced by internal charge pump. Con-
trolled by the SHDN input pin. Output voltage on this pin
will be approximately 2.5 times V
CC
or 7.25V, whichever is
less.
V
CC
(Pin 5): Input Supply Voltage. Range from 1.8V to
5.5V.
LTC1982:
SHDN 1 (Pin 1): SHDN 1 Active Low Input. Used to shut
down the GATE 1 charge pump and force the GATE 1
output pin to ground.
GND (Pin 2): Ground.
SHDN 2 (Pin 3): SHDN 2 Active Low Input. Used to shut
down the GATE 2 charge pump and force the GATE 2
output pin to ground.
LTC1981/LTC1982
5
OPERATIO
U
Charge Pump
To fully enhance the external N-channel switches, internal
charge pumps are used to boost the output gate drive to
approximately 2.5 times the supply voltage, or 7.25V,
whichever is less. A feedback network is used to regulate
the output gate drive. This keeps the supply current low in
addition to providing a maximum output voltage limit. The
reason for the maximum output voltage limit is to avoid
switch gate source breakdown due to excessive gate
overdrive.
The gate drive outputs (GATE 1, GATE 2, or GATE) are
controlled by the shutdown input pins (SHDN 1, SHDN 2
or SHDN). A logic high input on one of the shutdown input
pins enables the corresponding charge pump and drives
the related gate drive output pin high. A logic low input on
one of the shutdown input pins disables the correspond-
ing charge pump and drives the related gate drive output
pin low. If shutdown input on the LTC1981 is low or both
of the shutdown input pins on the LTC1982 are low, the
part will be placed into a low current shutdown mode
(<1µA).
Gate Drive Ready (LTC1981 Only)
The gate drive ready pin (GDR) is used to indicate when the
gate drive output (GATE) is greater than 90% of its final
value. This can be useful in applications that require
knowledge of the state of the gate drive for initialization
purposes or as fault detection should something be load-
ing the gate drive down.
BLOCK DIAGRA SM
W
LTC1981 Single High Side Switch Driver
LTC1982 Dual High Side Switch Driver
REGULATING
CHARGE PUMP
EN
+
–
+
–
GATE
GDR
V
CC
REF
SHDN
1981/82 BD01
15k
REGULATING
CHARGE
PUMP 1
EN GATE 1
SHDN 1
REGULATING
CHARGE
PUMP 2
EN GATE 2
SHDN 2
1981/82 BD02
30k
30k
GATE 2(Pin 4): Gate Drive Output to an External High Side
Switch. Fully enhanced by internal charge pump. Con-
trolled by the SHDN 2 input pin. Output voltage on this pin
will be approximately 2.5 times V
CC
or 7.25V, whichever is
less.
GATE 1 (Pin 5): Gate Drive Output to an External High Side
Switch. Fully enhanced by internal charge pump. Con-
trolled by the SHDN 1 input pin. Output voltage on this pin
will be approximately 2.5 times V
CC
or 7.25V, whichever is
less.
V
CC
(Pin 6): Input Supply Voltage. Range from 1.8V to␣ 5.5V.
PIN FUNCTIONS
UUU
LTC1981/LTC1982
6
APPLICATIONS INFORMATION
WUUU
Figure 3. Direct Interface to 3.3V Logic
V
CC
GATE 1
SHDN 1 GND
1/2 LTC1982
5V
LOAD
1981/82 F03
3.3V
5V
Si3442DV
Figure 1. Powering a Large Capactive Load
Figure 2. Direct Interface to 5V Logic
Logic-Level MOSFET Switches
The LTC1981/LTC1982 are designed to operate with logic-
level N-channel MOSFET switches. Although there is some
variation among manufacturers, logic-level MOSFET
switches are typically rated with V
GS
= 4V with a maximum
continuous V
GS
rating of ±8V. RDS (ON) and maximum
V
DS
ratings are similar to standard MOSFETs and there is
generally little price differential. When operating at supply
voltages of 5V or greater, care must be taken when
selecting the MOSFET. The LTC1981/LTC1982 limit the
output voltage to between 6.9V and 7.5V. The V
GS
devel-
oped for the MOSFET may be too low to sufficiently turn on
the MOSFET. MOSFETs rated at 2.5V, or less, will be better
suited for applications where the supply voltages ap-
proach 5V.
Powering Large Capacitive Loads
Electrical subsystems in portable battery-powered equip-
ment are typically bypassed with large filter capacitors to
reduce supply transients and supply induced glitching. If
not properly powered however, these capacitors may
themselves become the source of supply glitching. For
example, if a 100µF capacitor is powered through a switch
with a slew rate of 0.1V/µs, the current during start-up is:
I
START
= C(∆V/∆t)
= (100 • 10
–6
)(1 • 10
5
)
= 10A
Obviously, this is too much current for the regulator (or
output capacitor) to supply and the output will glitch by as
much as a few volts.
The start up current can be substantially reduced by
limiting the slew rate at the gate of an N-channel as shown
in Figure 1. The gate drive output of the LTC1981/LTC1982
have an internal 30k resistor (15k LTC1981) in series with
each of the output gate drive pins (see Functional Block
Diagram). Therefore, it only needs an external 0.1µF
capacitor (0.22µF for the LTC1981) to create enough RC
delay to substantially slow the slew rate of the MOSFET
gate to approximately 0.6V/ms. Since the MOSFET is
operating as a source follower, the slew rate at the source
is essentially the same as that at the gate, reducing the
startup current to approximately 60mA which is easily
managed by the system regulator. R1 is required to
eliminate the possibility of parasitic MOSFET oscillations
during switch transitions. It is a good practice to isolate the
gates of paralleled MOSFETs with 1k resistors to decrease
the possibility of interaction between switches.
Mixed 5V/3V Systems
Because the input ESD protection diodes are referenced to
the GND pin instead of the supply pin, it is possible to drive
the LTC1981/LTC1982 inputs from 5V CMOS or TTL logic
even though the LTC1981/LTC1982 is powered from a
3.3V supply as shown in Figure 2. Likewise, because the
input threshold voltage high is never greater than 1.6V, the
reverse situation is true. The LTC1981/LTC1982 can be
driven with 3V CMOS or TTL even when the supply to the
device is as high as 5V as shown in Figure 3.
V
CC
GATE 1
SHDN 1 GND
1/2 LTC1982
+
LT1129-3.3
+
V
IN
ON/OFF
3.3µF
R1
1k
C1
0.1µFC
L
100µF
3.3V
LOAD
1981/82 F01
3.3V
Si3442DV
VCC GATE 1
SHDN 1 GND
1/2 LTC1982
3.3V
LOAD
1981/82 F02
3.3V
Si3442DV
5V
LTC1981/LTC1982
7
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) unless otherwise noted.
S5 Package
5-Lead Plastic SOT-23
(LTC DWG # 05-08-1633)
APPLICATIONS INFORMATION
WUUU
S6 Package
6-Lead Plastic SOT-23
(LTC DWG # 05-08-1634)
0.95
(0.037)
REF
1.50 – 1.75
(0.059 – 0.069)
0.35 – 0.55
(0.014 – 0.022) 0.35 – 0.50
(0.014 – 0.020)
FIVE PLACES (NOTE 2)
S5 SOT-23 0599
2.80 – 3.00
(0.110 – 0.118)
(NOTE 3)
1.90
(0.074)
REF
0.90 – 1.45
(0.035 – 0.057)
0.90 – 1.30
(0.035 – 0.051)
0.00 – 0.15
(0.00 – 0.006)
0.09 – 0.20
(0.004 – 0.008)
(NOTE 2)
2.60 – 3.00
(0.102 – 0.118)
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DIMENSIONS ARE INCLUSIVE OF PLATING
3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
4. MOLD FLASH SHALL NOT EXCEED 0.254mm
5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)
0.95
(0.037)
REF
1.50 – 1.75
(0.059 – 0.069)
0.35 – 0.55
(0.014 – 0.022) 0.35 – 0.50
(0.014 – 0.020)
SIX PLACES (NOTE 2)
S6 SOT-23 0898
2.80 – 3.00
(0.110 – 0.118)
(NOTE 3)
1.90
(0.074)
REF
0.90 – 1.45
(0.035 – 0.057)
0.90 – 1.30
(0.035 – 0.051)
0.00 – 0.15
(0.00 – 0.006)
0.09 – 0.20
(0.004 – 0.008)
(NOTE 2)
2.6 – 3.0
(0.110 – 0.118)
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DIMENSIONS ARE INCLUSIVE OF PLATING
3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
4. MOLD FLASH SHALL NOT EXCEED 0.254mm
5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)
Figure 4. Reverse Battery Protection
V
CC
GATE
SHDN
GND
GDR
LTC1981
LOAD
1981/82 F04
3V
V
BAT
(1.8V TO 5V)
Si3442DV
10k
10k
0.1µF
1
2
3
5
4
150Ω
GATE
DRIVE
READY
Reverse Battery Protection
The LTC1981/LTC1982 can be protected against reverse
battery conditions by connecting a 150Ω resistor in series
with the supply pin as shown in Figure 4. The resistor
limits the supply current to less than 24mA with –3.6V
applied. Because the LTC1981/LTC1982 draw very little
current while in normal operation, the drop across the
resistor is minimal. Control logic can be protected by
adding 10k resistors in series with the input pins.
LTC1981/LTC1982
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 2000
sn19812 19812fs LT/LCG 1200 4K • PRINTED IN USA
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Driving Both High Side and Low Side Switches
U
TYPICAL APPLICATIO
SHDN 1
GND
SHDN 2
LTC1982
GATE 1
GATE 2
V
CC
SHDN 1
SHDN 2
HIGH SIDE
LOAD
LOW SIDE
LOAD
10µF
0.1µF
0.1µF
1k
1k Q1
Si6954DQ
Q2
Si6954DQ
V
CC
1.8 to 5.0V V
EXT
(30V MAX)
1981/82 • TA03
1
2
3
6
5
4
