LTC7000/LTC7000-1
Fast 150V Protected
High Side NMOS Static Switch Driver
FEATURES
DESCRIPTION
Wide Operating VIN: 3.5V to 135V (150V Abs Max)
n 1Ω Pull-Down, 2.2Ω Pull-Up for Fast Turn-On and
Turn-Off Times with 35ns Propagation Delays
n Internal Charge Pump for 100% Duty Cycle
n Short-Circuit Protected
n Adjustable Current Trip Threshold (LTC7000)
n Current Monitor Output (LTC7000)
n Automatic Restart Timer
n Open-Drain Fault Flag
n Adjustable Turn-On Slew Rate
n Gate Driver Supply from 3.5V to 15V
n Adjustable V Undervoltage and Overvoltage
IN
Lockouts (LTC7000)
n Adjustable Driver Supply V
CC Undervoltage Lockout
n Low Shutdown Current: 1µA
n CMOS Compatible Input
n Thermally Enhanced, High Voltage Capable 16-Lead
MSOP Packages
n AEC-Q100 Qualified for Automotive Applications
The LTC®7000/LTC7000-1 is a fast high side N-channel
MOSFET gate driver that operates from input voltages up
to 135V. It contains an internal charge pump that fully
enhances an external N-channel MOSFET switch, allowing
it to remain on indefinitely.
n
APPLICATIONS
Static Switch Driver
n Load and Supply Switch Driver
n Electronic Valve Driver
n High Frequency High Side Gate Driver
n
Its powerful driver can easily drive large gate capacitances
with very short transition times, making it well suited for
both high frequency switching applications or static switch
applications that require a fast turn-on and/or turn-off time.
When an internal comparator senses that the switch
current has exceeded a preset level, a fault flag is asserted
and the switch is turned off after a period of time set by
an external timing capacitor. After a cooldown period, the
LTC7000/LTC7000-1 automatically retries.
The LTC7000/LTC7000-1 is available in the thermallyenhanced 16-lead MSOP packages.
LTC7000
LTC7000-1
16-Lead MSOP
MSE16
16-Lead MSOP
MSE16(12)
High Voltage Pin Spacing
0.157mm
0.657mm
RUN/OVLO/ISET/IMON Pins
Yes
No
Package
All registered trademarks and trademarks are the property of their respective owners.
TYPICAL APPLICATION
High Side Switch with 100% Duty Cycle and Overcurrent Protection
Turn-On Transient Waveform
VIN
3.5V TO 135V
VCC
1µF
100k
1nF OFF ON
VIN = 135V
SNS+
VIN
LTC7000-1
SNS–
FAULT
TGUP
TIMER
TGDN
BST
INP
VCCUV
GND
TS
0.007Ω
100Ω
0.1µF
LOAD
3.5V TO 135V
3A CONTINUOUS MAX
7000 TA01a
VINP
2V/DIV
VLOAD
50V/DIV
20ns/DIV
7000 TA01b
Rev. E
Document Feedback
For more information www.analog.com
1
LTC7000/LTC7000-1
TABLE OF CONTENTS
Features............................................................................................................................. 1
Applications........................................................................................................................ 1
Typical Application ................................................................................................................ 1
Description......................................................................................................................... 1
Absolute Maximum Ratings...................................................................................................... 3
Pin Configuration.................................................................................................................. 3
Order Information.................................................................................................................. 3
Electrical Characteristics......................................................................................................... 5
Typical Performance Characteristics........................................................................................... 7
Pin Functions....................................................................................................................... 9
Block Diagram.....................................................................................................................10
Timing Diagram...................................................................................................................11
Operation..........................................................................................................................11
Applications Information........................................................................................................13
Package Description.............................................................................................................27
Revision History..................................................................................................................29
Typical Application...............................................................................................................30
Related Parts......................................................................................................................30
Rev. E
2
For more information www.analog.com
LTC7000/LTC7000-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltages
VIN........................................................ –0.3V to 150V
BST-TS.................................................... –0.3V to 15V
VCC......................................................... –0.3V to 15V
TS Voltage................................................... –6V to 150V
BST, SNS+ and SNS– Voltages ................. –0.3V to 150V
SNS+ – SNS–
Continuous.......................................... –0.3V to +0.3V
The VCC pin provides the power for the MOSFET gate
drivers and internal circuitry. The LTC7000/LTC7000-1
features an internal P-channel low dropout regulator
(LDO) that can supply power at VCC from the VIN supply
pin or VCC can be driven from an external power supply.
If the internal P-channel LDO is used to power VCC, it
must have a minimum 1.0µF low ESR ceramic capacitor to
ensure stability and should not be connected to any other
circuitry other than optionally biasing some pins on the
LTC7000/LTC7000-1 (FAULT, INP or TIMER).
Maximum switching
frequency with internal LDO <
BST
TS
VCC Generation
30µA
2 • MOSFET Q G
≅ 500Hz
A Schottky diode should not be used between VCC and
BST, as the reverse leakage of the Schottky diode at hot
will be more current than the charge pump can overcome.
Some example silicon diodes with low leakage include:
• MMBD1501A - Fairchild Semiconductor
• CMPD3003 - Central Semiconductor
1mA
2 • MOSFET Q G
≅ 20kHz
For higher gate charge applications, an external silicon
diode between VCC and BST should be used and VCC
can be driven from a high efficiency external supply. VCC
should never be driven higher than VIN or permanent
damage to the LTC7000/LTC7000-1 could occur.
VCC Undervoltage Comparator
The LTC7000/LTC7000-1 contains an adjustable
undervoltage lockout (UVLO) on the VCC voltage that
pulls TGDN to TS and can be easily programmed using a
resistor (RVCCUV) between the VCCUV pin and ground. The
voltage generated on VCCUV by RVCCUV and the internal
10µA current source set the VCC UVLO. The rising VCC
UVLO is internally limited within the range of 3.5V and
10.5V. If VCCUV is open the rising VCC UVLO is set internally
to 7.0V. The typical value of resistor for a particular rising
VCC UVLO can be selected using Figure 11 or the following
equation:
R VCCUV =
Rising VCC UVLO
70µA
Rev. E
18
For more information www.analog.com
LTC7000/LTC7000-1
APPLICATIONS INFORMATION
Limiting Inrush Current During Turn-On
Where 3.5V < Rising VCC UVLO < 10.5V.
11
10
9
VCC UVLO (V)
8
7
6
5
4
3
2
RISING VCC UVLO
FALLING VCC UVLO
1
0
0
30 60 90 120 150 180 210 240
VCCUV RESISTOR TO GROUND (kΩ)
7000 F11
Figure 11. VCCUV Resistor Selection
MOSFET Selection
The most important parameters in high voltage applications for MOSFET selection are the breakdown voltage
BVDSS, on-resistance RDS(ON) and the safe operating area,
SOA.
The MOSFET, when off, will see the full input range of the
input power supply plus any additional ringing than can
occur when driving inductive loads.
Driving large capacitive loads such as complex electrical
systems with large bypass capacitors should be powered
using the circuit shown in Figure 12. The pull-up gate
drive to the power MOSFET from TGUP is passed through
an RC delay network, RG and CG, which greatly reduces
the turn-on ramp rate of the MOSFET. Since the MOSFET
source voltage follows the gate voltage, the load is powered smoothly from ground. This dramatically reduces
the inrush current from the source supply and reduces
the transient ramp rate of the load allowing for slower
activation of sensitive electrical loads. The turn-off of the
MOSFET is not affected by the RC delay network as the
pull-down for the MOSFET gate is directly from the TGDN
pin. Note that the voltage rating on capacitor CG needs
to be the same or higher than the external MOSFET and
CLOAD.
Adding CG to the gate of the external MOSFET can cause
high frequency oscillation. A low power, low ohmic value
resistor (10Ω) should be placed in series with CG to
dampen the oscillations as shown in Figure 12 whenever
CG is used in an application. Alternatively, the low ohmic
value resistor can be placed in series with the gate of the
external MOSFET.
External conduction losses are minimized when using low
RDS(ON) MOSFETs. Since many high voltage MOSFETs
have higher threshold voltages (typical VTH ≥ 5V) and
RDS(ON) is directly related to the (VGS–VTH) of the MOSFET,
the LTC7000/LTC7000-1 maximum gate drive of greater
than 10V makes it an ideal solution to minimize external
conduction losses associated with external high voltage
MOSFETs.
SOA is specified in Typical Characteristic curves in power
N-channel MOSFET data sheets. The SOA curves show
the relationship between the voltages and current allowed
in a timed operation of a power MOSFET without causing
damage to the MOSFET. The overcurrent trip point (RSNS
and RISET) of the LTC7000/LTC7000-1 and TIMER capacitor should be chosen to stay within the SOA region of the
MOSFET selected for the application.
LTC7000/
LTC7000-1
VIN
SNS+
SNS–
TGUP
TGDN
RFLT
RSNS
RG 100k
BST
TS
CB
1µF
7000 F12
10Ω
CG
0.047µF
CLOAD
100µF
LOAD
Figure 12. Powering Large Capacitive Loads
The values for RG and CG to limit the inrush current can
be calculated from the below equation:
IIN _ RUSH ≅
0.7 • 12V • CLOAD
R G • CG
Rev. E
For more information www.analog.com
19
LTC7000/LTC7000-1
APPLICATIONS INFORMATION
For the values shown in Figure 12 the inrush current will be:
IIN _ RUSH ≅
0.7 • 12V • 100µF
100kΩ • 0.047µF
≅ 180mA
Correspondingly, the ramp rate at the load for the circuit
in Figure 12 is approximately:
Δ VLOAD
ΔT
≅
0.7 • 12V
R G • CG
≅ 2V / ms
Reverse Current Protection
To protect the load from discharging back into VIN when
the external MOSFET is off and the VIN voltage drops
below the load voltage, two external N-channel MOSFETs
should be used and must be configured in a back-to-back
arrangement as shown in Figure 14. Dual N-channel
packages such as the Vishay/Siliconix Si7956DP are a
good choice for space saving designs.
VIN
When CG is added to the circuit in Figure 12, the value
of the bootstrap capacitor, CB, must be increased to be
able to supply the charge to both to MOSFET gate and
capacitor CG. The relationship for CB that needs to be
maintained when CG is used is given by:
LTC7000/
LTC7000-1
SNS–
TGUP
INP
M1A
M1B
LOAD
Figure 14. Protecting Load from Voltage Drops on VIN
When turning off a power MOSFET that is connected to
an inductive load (inductor, long wire or complex load),
the TS pin can be pulled below ground until the current in
the inductive load has completely discharged. The TS pin
is tolerant of voltages down to –6V, however, an optional
Schottky diode with a voltage rating at least as high as the
load voltage should be connected between TS and ground
to prevent discharging the load through the TS pin of the
LTC7000/LTC7000-1. See Figure 13.
VIN
SNS+
RSNS
RFLT
TGUP
M1A
TGDN
L1
TS
7000 F13
RSNS
TS
7000 F14
Optional Schottky Diode Usage on TS
SNS–
RFLT
TGDN
MOSFET Q G
CB >
+ 10 • C G
1V
LTC7000/
LTC7000-1
SNS+
LOAD
D2
Figure 13. Optional Schottky Diode Usage
Design Example
As a design example, consider a fast power supply switch
with the following specifications: VIN = VLOAD = 8V to
135V, ILOAD = 3A, Insertion Loss < 0.5W at room temp
with maximum load, output rise time with a 1µF load
is 1V/µs (1A inrush current) and a shorted load should
immediately turn off the MOSFET.
The first item to select is the N-channel MOSFET. The
IRF7815PBF is selected because it has sufficient breakdown
voltage (BVDSS_MIN = 150V), sufficient continuous current
rating for a 3A load (ID_MAX = 4.1A) and the on-resistance
is low enough (RDS(ON)_MAX = 43mΩ) to be able to meet
the power loss specification.
Examining the MOSFET data sheet, the VGS vs RDS(ON)
typical performance curve shows a sharp increase in
RDS(ON) as the MOSFET VGS gets below 8.0V. Since the
default VCC UVLO is 7.0V, a resistor (RVCCUV ) should be
placed between VCCUV and ground to increase the VCC
Rev. E
20
For more information www.analog.com
LTC7000/LTC7000-1
APPLICATIONS INFORMATION
UVLO to 8.0V. The value of RVCCUV is calculated and
rounded to the nearest standard value as follows:
R VCCUV =
8.0V
70µA
= 113kΩ
The value of the current sense resistor, RSNS is calculated
next. The LTC7000-1 has a fixed current sense threshold, ΔVTH, of 30mV typical and 22mV minimum. To provide a minimum 3A load current, the minimum specified
ΔVTH = 22mV should be used for the RSNS calculation
below:
R SNS =
22mV
= 7.3mΩ
3A
The closest standard value is 7mΩ. The power dissipation
of RSNS is 63mW so choose a power rating of greater than
0.25W to provide adequate margin.
The next item to check is to make sure the insertion loss
specification is satisfied. The insertion loss is given by:
2
(
PLOSS = ILOAD • RDS(ON)(MAX) + R SNS
)
2
= 3A • ( 0.043Ω + 0.007Ω ) = 0.45W
Which meets the design specification of less than 0.5W.
The fast output slew rate specification of 1V/µs into a 1µF
load can be met by placing a resistor, RG, in series with
the TGUP pin to the MOSFET gate, as well as connecting
TGDN and a capacitor, CG, to ground on the MOSFET
gate. The values of RG and TG can be calculated from the
following expression:
R G • CG ≅
0.7 • 12V
1V / µs
= 8.4µs
CG needs to have a voltage rating as high as the BVDSS
of the MOSFET. A good choice for CG is the AVX
06032C471KAT2A which has a value of 470pF and a voltage rating of 200V. RG is then calculated to be 17.8kΩ.
The bootstrap capacitor CB can be calculated from the
gate charge as specified in the MOSFET data sheet and
CG as follows:
Q
30nC
CB > G + 10 • C G =
+ 10 • 470pF
1V
1V
≅ 0.33nF. 100nF will be used.
To meet the short-circuit specification, the TIMER pin
should be connected to VCC to enable immediate turn-off
(approximately 70ns) of the MOSFET in the case of an
overcurrent condition. If an overcurrent condition turns
off the MOSFET, it will not turn back on until the INP pin
has cycled low then back high.
The complete circuit is shown in Figure 15.
Turn–On Transient
VIN
8V TO 135V
SNS+
VIN
VCC
1µF
SNS–
TIMER
FAULT
LTC7000-1
TGUP
TGDN
100Ω
17.8k
INP
BST
VCCUV
113k
0.1µF
GND
0.007Ω
IRF7815TRPBF
10Ω
CG
470pF
200V
TS
LOAD
8V TO 135V
1µF 3A CONTINUOUS MODE
VINP
5V/DIV
VIN = 135V
VLOAD
50V/DIV
IDMOSFET
1A/DIV
50µs/DIV
7000 F15b
7000 F15
Figure 15. Design Example
Rev. E
For more information www.analog.com
21
LTC7000/LTC7000-1
APPLICATIONS INFORMATION
PC Board Layout Considerations
1. Solder the exposed pad on the backside of the LTC7000/
LTC7000-1 packages directly to the ground plane of the
board.
2. Kelvin connect the
resistor.
SNS+
pin to the current sense
3. Limit the resistance of the TS trace, by making it short
and wide.
4. CB needs to be close to chip.
5. Always include an option in the PC board layout to
place a resistor in series with the gate of any external MOSFET. High frequency oscillations are design
dependent and having the option to add a series dampening resistor can save a design iteration of the PC
board.
Pin Creepage and Clearance
In some higher voltage applications, the MSE16 package
may not provide sufficient PC board trace clearance
between high and low voltage pins. In applications where
clearance is required, the LTC7000-1 in the MSE16(12)
package can be used. The MSE16(12) package has
removed pins between all the adjacent high voltage
and low voltage pins, providing 0.657mm clearance,
which will be sufficient for most applications. For more
information, refer to the printed circuit board design
standards described in IPC-2221.
Rev. E
22
For more information www.analog.com
LTC7000/LTC7000-1
TYPICAL APPLICATIONS
Protected Redundant Supply Switchover with Shoot Through Protection
0.003Ω
MAIN POWER
7V TO 135V
2×
BSC320N20NS3G
2×
BSC320N20NS3G
LOAD
0.0015Ω
10µF
10µF
100Ω
100Ω
10Ω
10Ω
100Ω
1nF
0.1µF
SNS+
VIN
RUN
SNS– TGDN
TGUP
TS
200k
BST
INP
FAULT
LTC7000
6.98k
100k 1µF
GND
TIMER
OVLO
SNS+
VIN
RUN
NOTE: THE BACKUP PATH
WILL LATCH-OFF WITH AN
OVERCURRENT FAULT.
LTC7000
1µF
VCC
FAULT
VCCUV
IMON
ISET
0.1µF
TGDN SNS–
0.1µF
BST
VCC
INP
TIMER
OVLO
1nF
VBACKUP
7V TO 135V
100Ω
0.1µF
4.99k
TGUP
TS
0.1µF
10µF
GND
VCCUV
IMON
ISET
7000 TA02
VLOAD vs Main Power Voltage
80
VMAIN Falling Through 33V
VBACKUP = 60V
VTG–TS
MAIN
10V/DIV
VLOAD (V)
70
60
50
40
30
RLOAD = 50Ω
10
20
30 40 50 60
MAIN POWER (V)
70
VTG–TS
MAIN
10V/DIV
VTG–TS
BACKUP
10V/DIV
VTG–TS
BACKUP
10V/DIV
VLOAD
20V/DIV
VLOAD
20V/DIV
40µs/DIV
0
VMAIN Rising Through 36V
7000 TA02c
RLOAD = 50Ω
10µs/DIV
7000 TA02d
80
7000 TA02b
Rev. E
For more information www.analog.com
23
LTC7000/LTC7000-1
TYPICAL APPLICATIONS
High Side Switch with Input Overvoltage and Overcurrent Protection
VIN
3.5V TO 60V
(150V TOLERANT)
10µF
SNS+
VIN
RUN
OVLO
953k
19.6k
FAULT
1µF
LTC7000
100k
1nF
VCC
OFF ON
0.1µF
ISET
IMON
VCCUV
GND
INP
BSC12DN20NS3G
TS
TIMER
0.005Ω
100Ω
SNS–
TGUP
TGDN
BST
LOAD
3.5V TO 60V
10A CONTINUOUS MAX
150k
7000 TA03a
High Side Switch with Overcurrent Protection and Fault Latchoff
VIN
3.5V TO 135V
10µF
100k
1µF
RTIMER
10nF
SNS+
VIN
VCC
SNS–
FAULT
TIMER
LTC7000-1
100Ω
TGUP
TGDN
BSC12DN20NS3G
BST
0.1µF
TS
OFF ON
0.04Ω
INP
GND
VCCUV
LOAD
3.5V TO 135V
0.5A CONTINUOUS
7000 TA04a
RTIMER = OPEN
12Ω/100ms LOAD PULSE
RTIMER = 100k
12Ω/100mS LOAD PULSE
RLOAD
10kΩ/DIV
RLOAD
10kΩ/DIV
VLOAD
10V/DIV
VLOAD
10V/DIV
ILOAD
1A/DIV
ILOAD
1A/DIV
VTIMER
1A/DIV
VTIMER
1V/DIV
100ms/DIV
VIN = 12V
VINP = 4V
7000 TA04b
100ms/DIV
7000 TA04c
VIN = 12V
VINP = 4V
Rev. E
24
For more information www.analog.com
LTC7000/LTC7000-1
TYPICAL APPLICATIONS
Average Current Trip
VIN
3.5V TO
135V
VINP
D
Q
SNS+
INP
SNS–
TGUP
TGDN
RB
LTC7000
FAULT
249Ω
0.06Ω
SI7738DP
BST
100k
0.1µF
VCC
VCCUV
TIMER
OVLO
1µF
TS
IMON
ISET
GND
LOAD
3.5V TO 135V