LTC3815
6A Monolithic Synchronous DC/DC
Step-Down Converter with PMBus Interface
FEATURES
DESCRIPTION
2.25V to 5.5V Input Voltage Range
nn ±1% Total Output Voltage Accuracy Over
Temperature at VIN = 3.3V or 5V
nn Single Resistor-Programmable Output Voltage
nn PMBus Compliant Serial Interface:
nn Programmable Output Voltage Margining:
Up to ±25% VOUT Range with 0.1% Resolution
nn Read back of Average and Peak Temperature,
Current, and Voltage (25Hz Refresh Rate)
nn Fault Status
nn Phase-Lockable Fixed Frequency Up to 3MHz
nn Less Than 1ms Power-Up Time
nn Integrated 13-Bit ADC
nn Optional External Reference Input
nn Pin Selectable Fast-Margining of the Output Voltage
nn Power Good Flag with Pin Programmable Thresholds
and Filter Delay
nn Differential Remote Output Voltage Sensing
nn Master Shutdown Mode: 1V (Note 4)
VRUN_STBY = 0V, VRUN_MSIR > 1V
VRUN_MSTR = 0V, VSDA = VSCL ≥ VIN
VUVLO
VIN Undervoltage Reset
Hysterisis
VIN Rising
VIN Falling
IREF
Reference Current
(Note 10)
l
ΔIREF,LINE
Reference Current Line Regulation
VIN = 2.5V to 5.5V (Note 10)
l
ΔVOUT,OFFSET
Regulation Accuracy
ΔVOUT,OFFSET = (VCC_SEN – VSS_SEN) – VREF
VREF = 1.5V (Notes 5, 10)
l
ΔVOUT,MARGIN
Maximum Margining Range
Set Point Accuracy
MFR_VOUT_COMMAND = –25% to
25%, VREF = 1.5V (Note 5)
l
TYP
MAX
UNITS
Input Supply Range
l
2.25
5.5
V
Output Voltage Programming Range
l
0.4
72% of VIN
V
Resolution
LSD Step Size
5
120
1
8
200
mA
µA
µA
2.05
2.15
0.2
2.25
V
V
99.2
99.5
100
100
100.8
100.5
µA
µA
0.05
0.2
%/V
–0.5
0.5
%
–25
–0.5
25
0.5
%
%
9
0.1
Bits
%
NL_VOUT
DAC Nonlinearity
AEA
Error Amplifier Open Loop Gain
ITH = 1V (Note 5)
80
±1
dB
fBW
Error Amp Gain Bandwidth Product
(Note 6)
20
MHz
RIN
Differential Amplier Input Resistance
Measured at VCC_SEN Pin
160
tSS
Internal Soft-Start Time/VREF
External CSS = Float
ICSLEW
CSLEW Pull-Up Current
VCSLEW = 0V
ILIM
SW Valley Current Limit
Sourcing (Note 8)
Sinking
IRUN_STBY
Regulator On Source Current
VRUN_STBY = 0V
VRUN_MSTR
Regulator On Threshold (Master Shutdown)
Regulator On Hysterisis
Regulator Power-Down Threshold
Rising Edge
Falling Edge
IQ < 10μA
VRUN_STBY
Regulator On Threshold (Standby Mode)
IASEL
ASEL Programming Current
10
µA
IPGFD
PGFD Programming Current
10
µA
ISS
SS Current
VIH,MARGIN
VIL,MARGIN
MARGIN High Voltage
MARGIN Low Voltage
IWP
WP Pin Pull-Up Current
WP = 0V
10
µA
SRMARGIN
Reference Slew Rate During Margin Change
CSLEW = 1nF
CSLEW = OPEN
CSLEW = SVIN
0.1
23
10
%/ms
%/ms
%/µs
tINIT
Initialization Time
Delay from Power Applied Until
VOUT Ramp Up
kΩ
1
ms/V
–10
l
5.5
6.5
–6
µA
7.5
–2.5
0.9
0.7
VSS = 0V
4
1.1
1
1.2
5
A
A
µA
1
0.1
0.65
1.2
LSB
V
V
V
V
6
µA
0.4
V
V
1
2
ms
1.0
1.0
1.15
1.15
MHz
MHz
0.3
V
V
Oscillator and Power Switch
fOSC
Oscillator Frequency
VSYNC
SYNC Level High
SYNC Level Low
RT = 25.5k
RT = SVIN
l
0.85
0.85
1.2
Rev B
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3
LTC3815
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, VIN = 3.3V unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
VMODE
Discontinuous Mode Threshold
1
V
tON(MIN)
Minimum On-Time
75
ns
tOFF(MIN)
Minimum Off-Time
100
ns
RTOP
Top Power PMOS On Resistance
35
mΩ
RBOTTOM
Bottom Power NMOS On Resistance
θCLKOUT
CONDITIONS
MIN
TYP
MAX
UNITS
20
mΩ
180
Deg
Relative Phase of CLKOUT
MODE/SYNC = 0V
Default PGOOD Threshold
VPGLIM = VIN, VOUT >1V
±8
±10
±12
%
VPGLIM/VREF = 0.19, VOUT ≥ 1V
VPGLIM/VREF = 0.38
±6
±13
±10
±30
±9
±17
%
%
±5
µA
0.1
0.3
V
190
1.6
24
250
2.2
32.5
µs
ms
ms
PGOOD
VPGOOD,DEFAULT
VPGOOD,PROGRAM Program PGOOD Threshold
ILEAK
PGOOD Leakage Current
VOL
PGOOD Output Low Voltage
IOUT = 3mA
tPGFD
PGOOD Filter Delay
PGFD = 0V
PGFD = 0.65V
PGFD = VIN
150
1.0
17
Output Voltage Readback
N
Resolution
LSB Step Size
VF/S
Full Scale Output Voltage
VOUT_TUE
Total Unadjusted Error
tCONVERT
Conversion Time
(Note 9)
13
0.5
Bits
mV
16.4
V
±0.75
±0.5
l
%
%
40
ms
13
4
Bits
mV
131
V
Input Voltage Readback
N
Resolution
LSB Step Size
VF/S
Full Scale Input Voltage
VIN_TUE
Total Unadjusted Error
tCONVERT
Conversion Time
(Note 9)
±1.5
l
%
40
ms
Bits
mA
Output Current Readback
N
Resolution
LSB Step Size
13
10
VF/S
Full Scale Output Current
±82
IOUT_TUE
Total Unadjusted Error
tCONVERT
Conversion Time
A
±3
%
40
ms
Input Current Readback
N
Resolution
LSB Step Size
13
10
Bits
mA
VF/S
Full Scale Input Current
±82
A
IIN_TUE
Total Unadjusted Error
tCONVERT
Conversion Time
4
±3
40
%
ms
Rev B
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LTC3815
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, VIN = 3.3V unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Temperature Readback
N
Resolution
LSB Step Size
9
1
Bits
°C
VF/S
Full Scale Temperature
±256
°C
TTUE
Total Unadjusted Error
±3
°C
tCONVERT
Conversion Time
40
ms
PMBus Interface Parameters
VIH, SDA, SCL
Input High Voltage
2.1
VIL, SDA, SCL
Input Low Voltage
IIH, SDA, SCL
Input Leakage Current
0V ≤ VPIN ≤ 5.5V
VOL, SDA
Output Low Voltage (SDA)
ISDA = 3mA
VOL, ALERT
Output Low Voltage (ALERT)
IALERT = 1mA
0.4
V
fSCL
Serial Bus Operating Frequency
10
400
kHz
tBUF
Bus Free Time Between Stop and Start
Condition
1.3
µs
tHD_SDA
Hold Time After (Repeated) Start Condition
0.6
µs
tSU_SDA
Repeated Start Condition Setup Time
0.6
µs
tSU_STO
Stop Condition Setup Time
0.6
tHD_DAT(OUT)
Data Hold Time
300
tHD_DAT(IN)
Input Data Hold Time
0
ns
tSU_DAT
Data Set-Up Time
100
ns
tLOW
Clock Low Period
1.3
tHIGH
Clock High Period
tTIMEOUT_SMB
Stuck PMBus Timer
where θJA (in °C/W) is the package thermal impedance.
–5
0.8
V
5
µA
0.4
V
µs
900
10000
0.6
Measured from Last PMBus Start
Event
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 LTC3815 is tested under pulsed load conditions such that TJ ≈ TA.
The LTC3815E is guaranteed to meet specifications from 0°C to 85°C
junction temperature. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3815I is guaranteed
over the –40°C to 125°C operating junction temperature range. Note that
the maximum ambient temperature consistent with these specifications
is determined by specific operating conditions in conjunction with board
layout, the rated package thermal impedance and other environmental
factors.
Note 3: The junction temperature (TJ, in °C) is calculated from the ambient
temperature (TA, in °C) and power dissipation (PD, in Watts) according to
the formula:
TJ = TA + (PD • θJA)
V
ns
µs
µs
30
ms
Note 4 : The dynamic input supply current is higher due to power
MOSFET gate charging (QG × fOSC). See applications Information for more
information.
Note 5: The LTC3815 is tested in a feedback loop that servos VFB to a
referenced voltage with the ITH pin forced to a voltage between 0.6V
and 1V.
Note 6: Guaranteed by design, not subject to test.
Note 7: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum junction temperature
may impair device reliability or permanently damage the device.
Note 8: The LTC3815 uses valley current mode control so the current
limits specified correspond to the valley of the inductor current waveform.
Maximum load current is higher and equals the valley current limit ILIM
plus one half of the inductor ripple current.
Note 9: The maximum input and output voltage is 5.5V.
Note 10: Total output accuracy is the sum of the tolerances of IREF,
RREF(EXTERNAL), ∆VOUT,OFFSET, and ∆IREF,LINE • ∆VIN.
Rev B
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5
LTC3815
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current
100
100
VIN = 3.3V, VOUT = 1.8V
fSW = 1MHz
90
VOUT = 1.0V
CCM Mode
90
80
EFFICIENCY (%)
70
EFFICIENCY (%)
Load Step
(Forced Continuous Mode)
Efficiency vs Input Voltage
60
50
40
VOUT
50mV/DIV
80
ILOAD
5A/DIV
70
30
LOAD = 1A, f = 1MHz
LOAD = 6A, f = 1MHz
LOAD = 1A, f = 2MHz
LOAD = 6A, f = 2MHz
60
20
CCM Mode
DCM Mode
10
0
0.01
0.1
1
LOAD CURRENT (A)
10
50
2
3
4
5
INPUT VOLTAGE (V)
3815 G03
10µs/DIV
VOUT = 1V
ILOAD = 0A TO 5A
CCM MODE
FRONT PAGE CIRCUIT
6
3815 G02
3815 G01
Load Step
(Discontinuous Mode)
Output Margining
Load Regulation
0.20
VIN = 3.3V
MARGIN
2V/DIV
0.10
VOUT ERROR (%)
VOUT
50mV/DIV
VOUT
200mV/DIV
ILOAD
5A/DIV
CSLEW
1V/DIV
10µs/DIV
VOUT = 1V
ILOAD = 0A TO 5A
DCM MODE
FRONT PAGE CIRCUIT
3815 G04
0
–0.10
1ms/DIV
MARGIN REGISTERS PRE-LOADED
TO 10% AND –10%
CSLEW = 10pF
3815 G05
–0.20
–6
–4
–2
0
2
LOAD CURRENT (A)
4
6
3815 G06
Line Regulation
Forced Continuous Mode
Operation
Discontinuous Mode Operation
0.20
VOUT ERROR (%)
0.10
0
VOUT
20mV/DIV
VOUT
20mV/DIV
IL
1A/DIV
IL
1A/DIV
–0.10
–0.20
IOUT = 6A
CCM MODE
FRONT PAGE CIRCUIT
2
3
4
5
INPUT VOLTAGE (V)
6
5µs/DIV
VOUT = 1.8V
ILOAD = 100mA
VMODE = 3.3V
FRONT PAGE CIRCUIT
3815 G08
1µs/DIV
VOUT = 1.8V
ILOAD = 100mA
VMODE = 0V
FRONT PAGE CIRCUIT
3815 G09
3815 G07
6
Rev B
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LTC3815
TYPICAL PERFORMANCE CHARACTERISTICS
Current Sense Threshold
vs ITH Voltage
8
6.3
6
6.2
4
6.1
6.0
5.9
5.8
7.0
6.5
2
0
–2
–6
2
3
4
5
INPUT VOLTAGE (V)
–8
6
0
0.2
0.4
0.6
0.8
ITH VOLTAGE (V)
3815 G10
0
50
100
TEMPERATURE (°C)
150
3815 G12
Quiescent Current vs Input
Voltage
4
10
3
1
0
–1
–2
8
2
SUPPLY CURRENT (mA)
2
FREQUENCY VARIATION (%)
FREQUENCY VARIATION (%)
5.0
–50
1.2
Oscillator Frequency vs Input
Voltage
3
1
0
–1
–2
6
4
2
–50°C
25°C
125°C
–3
–3
–50
0
50
100
TEMPERATURE (°C)
–4
150
2
3
3815 G13
4
5
INPUT VOLTAGE (V)
0
6
2
1
2
3
4
5
INPUT VOLTAGE (V)
6
3815 G16
6
Oscillator Frequency vs RT
150
FREQUENCY (MHz)
STANDBY CURRENT (µA)
3
4
5
INPUT VOLTAGE (V)
3
200
4
3
3815 G15
Standby Current vs Input Voltage
5
–50°C
25°C
125°C
2
3815 G14
Shutdown Current vs Input
Voltage
SHUTDOWN CURRENT (µA)
1.0
3815 G11
Oscillator Frequency
vs Temperature
0
6.0
5.5
–4
5.7
5.6
Valley Current Limit vs
Temperature
CURRENT LIMIT (A)
6.4
CURRENT LIMIT (A)
CURRENT LIMIT (A)
Valley Current Limit
vs Input Voltage
100
1
50
0
–50°C
25°C
125°C
2
3
4
5
INPUT VOLTAGE (V)
6
3815 G17
0.2
0
20
40
60
RT (kΩ)
80
100
3815 G18
Rev B
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7
LTC3815
TYPICAL PERFORMANCE CHARACTERISTICS
1.0
VOUT Measurement Error vs VOUT
0.50
VOUT Command INL
0.50
VOUT Command DNL
0
0
–0.25
–0.5
–1.0
0.25
DNL (LSB)
0.25
0.5
INL (LSB)
MEASUREMENT ERROR (%)
VIN = 5V
0
1
2
3
OUTPUT VOLTAGE (V)
4
–0.25
–0.50
–25
5
–12.5
0
12.5
MFR_VOUT_COMMAND VALUE (%)
0.05
0
–0.05
–0.10
–2
0
2
4
OUTPUT CURRENT (A)
4
3.5V TO 1.8V
CCM MODE
FRONT PAGE CIRCUIT
IOUT = 0 TO 6A
0
–0.05
0
0.5
1
1.5
2
INPUT CURRENT (A)
2.5
3815 G22
0
–4
–50
3
IREF vs Temperature
0.1
0.25
0
–0.1
3
4
5
INPUT VOLTAGE (V)
6
3815 G25
8
IREF VARIATION (%)
–0.1
2
0
25
50
75
TEMPERATURE (°C)
–0.2
–50
100
125
IREF vs Input Voltage
0.50
–0.5
–25
3815 G24
0.2
–0.4
VIN = 2.5V, 1MHz
VIN = 3.3V, 1MHz
VIN = 5V, 1MHz
VIN = 3.3V, 2MHz
VIN = 5V, 2MHz
–2
0
IREF VARIATION (%)
MEASUREMENT ERROR (%)
2
3815 G23
VIN Measurement Error vs VIN
25
IIN, IOUT Measurement Error vs
Temperature, VIN and Frequency
IIN Measurement Error vs IIN
0.05
–0.10
6
–0.3
–12.5
0
12.5
MFR_VOUT_COMMAND VALUE (%)
3815 G21
MEASUREMENT ERROR (%)
0.10
MEASUREMENT ERROR (A)
MEASUREMENT ERROR (A)
IOUT Measurement Error vs IOUT
3.5V to 1.0V
CCM MODE
FRONT PAGE CIRCUIT
–0.50
–25
25
3815 G20
3815 G19
0.10
0
0
–0.25
0
50
100
TEMPERATURE (°C)
150
3815 G26
–0.50
2
3
4
5
INPUT VOLTAGE (V)
6
3815 G27
Rev B
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LTC3815
TYPICAL PERFORMANCE CHARACTERISTICS
Normal Start-Up
Start-Up Into Pre-Biased Output
RUN
2V/DIV
RUN
2V/DIV
VOUT
0.5V/DIV
VOUT
0.5V/DIV
PGOOD
2V/DIV
PGOOD
2V/DIV
IL
1A/DIV
IL
1A/DIV
500µs/DIV
VOUT = 1V
MODE = 0
FRONT PAGE CIRCUIT
3815 G28
3815 G29
Switch Leakage
vs Temperature, Main Switch
10
SYNCHRONOUS SWITCH
MAIN SWITCH
RDS(ON) (mΩ)
30
20
10
9
SWITCH LEAKAGE (µA)
50
40
40
30
20
10
2
3
4
5
INPUT VOLTAGE (v)
0
50
100
TEMPERATURE (°C)
5
4
3
0
12
Minimum VIN vs Load, VOUT and
Frequency
40
11
3.5
VOUT=1.2V, 1MHz
VOUT=1.2V, 2MHz
VOUT=1.8V, 1MHz
VOUT=1.8V, 2MHz
33
6
5
3
3.0
27
MINIMUM VIN (V)
SUPPLY CURRENT (mA)
8
20
13
0
50
100
TEMPERATURE (°C)
150
3815 G34
2.5
2.0
7
2
150
3815 G33
Dynamic Supply Current
vs Input Voltage
9
50
100
TEMPERATURE (°C)
3815 G32
Switch Leakage vs Temperature,
Synchronous Switch
SWITCH LEAKAGE (µA)
6
0
–50
150
3815 G31
0
–50
8
1
0
–50
6
3815 G30
500µs/DIV
60
SYNCHRONOUS SWITCH
MAIN SWITCH
50
RDS(ON) (mΩ)
IL
5A/DIV
Switch On-Resistance
vs Temperature
60
0
VOUT
0.5V/DIV
500µs/DIV
VOUT = 1V
MODE = 0
FRONT PAGE CIRCUIT
Switch On-Resistance
vs Input Voltage
VOUT Short and Recovery
0
1MHz
2MHz
2
3
4
5
INPUT VOLTAGE (v)
6
3815 G35
1.5
0
1
2
3
4
LOAD CURRENT (A)
5
6
3815 G36
Rev B
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9
LTC3815
PIN FUNCTIONS
RT (Pin 1): Oscillator Frequency. This pin provides two
modes of setting the constant switching frequency.
Connect a resistor from RT pin to ground to program the
switching frequency from 400kHz to 3MHz. Tying this
pin to VIN enables the internal 1MHz oscillator frequency.
ASEL (Pin 2): Serial Bus Address Configuration Input.
Connect a ±1% resistor from this pin to ground in order
to select the 3 LSBs of the serial bus interface address.
(see Table 7).
MARGIN (Pin 3): Fast Margining Select. In the default
mode when this pin is floating, the reference voltage
margin offset is changed with MFR_VOUT_COMMAND
through the serial interface. If this pin is pulled high, the
reference voltage margin offset is immediately ramped to
the value pre-stored in the MFR_VOUT_MARGIN_HIGH
register. If this pin is pulled low, the reference voltage margin offset is immediately ramped to the value pre-stored
in MFR_VOUT_MARGIN_LOW register.
WP (Pin 4): Write Protect Pin. Pulling this pin high disables writes to MFR_VOUT_COMMAND, MFR_VOUT_
MARGIN_HIGH, and MFR_VOUT_MARGIN_LOW. When
this pin is grounded, there are no write restrictions.
ALERT (Pin 5): Open Drain Digital Output. Connect the
system SMBALERT interrupt signal to this pin. A pull-up
resistor is required in the application.
CLKOUT (Pin 6): Clock Out Signal for 2-Phase Operation.
The phase of this clock is 180° with respect to the internal
clock. Signal swing is from VIN to GND.
SDA (Pin 7): Serial Bus Data Input and Output. A pull-up
resistor is required in the application.
SCL (Pin 8): Serial Bus Clock Input. A pull-up resistor is
required in the application.
MODE/SYNC (Pin 9): Mode Selection and External Clock
Input. If this pin is tied to VIN, discontinuous mode is
enabled at light loads. If this pin is connected to ground,
forced continuous mode is selected. Driving the MODE/
SYNC pin with an external clock signal will synchronize
the switching frequency to the applied frequency. There
is an internal 20k resistor to ground on this pin.
10
SW (Pins 10, 11, 13, 14, 18, 19, 21, 22, 23): Switching
Node. This pin connects to the drains of the internal main
and synchronous power MOSFET switches.
NC (Pins 12, 20): No Connection. Can be connected to
ground or left open. This pin does not connect to any
internal circuitry.
PVIN (Pins 15-17): Power Input Supply. PVIN connects to
the source of the internal P-channel power MOSFET. This
pin is independent of VIN and may be connected to the
same voltage or to a lower voltage supply.
PGOOD (Pin 29): Power Good. This open-drain output
is pulled down to SGND on start-up and while the output voltage is outside the power good window set by
the PGLIM pin. If the output voltage increases and stays
inside the power good window for more than the delay
programmed at the PGFD pin, the PGOOD pin is released.
If the output voltage leaves the power good window for
more than 16 switching cycles the PGOOD pin is pulled
down.
VIN (Pin 24): Signal Input Supply. Decouple this pin to
SGND with a capacitor. This pin powers the internal control circuitry. This pin is independent of PVIN and may
be connected to the same voltage or to a higher supply
voltage.
PGFD (Pin 25): PGOOD Deglitch Filter Delay Select. The
voltage at this pin sets the delay that the output must be
in regulation before the PGOOD flag is asserted. The delay
can be programmed to one of seven discrete values where
tDELAY = 200μs • 2N (N = 0 to 5, 7).
RUN_MSTR (Pin 26): Master Run. The power up threshold is set at 1V. When forced below 0.4V, all circuitry is
shut off and the IC is put into a low current shutdown
mode (IQ < 1μA).
RUN_STBY (Pin 27): Standby Mode Off. The regulator
power up threshold is set at 1V. When forced below 0.4V,
only the voltage regulator is shut off while the ADC and
PMBus interface are still active. When shut off, the ADC
refresh rate is reduced to 1Hz and the IC quiescent current
Rev B
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LTC3815
PIN FUNCTIONS
is reduced to 120μA. This pin sources 2.5μA. Do not pull
up with a low impedance ( PGOOD High Threshold
Yes
Yes
6
OFF
No Power to the Output (Note 2)
No
No
7
Busy
Not Implemented
8
Unknown
Not Implemented
9
Other
Not Implemented
No
No
Yes
Yes
Yes
Yes
10
Fans
Not Implemented
11
PGOOD
Inverted state of PGOOD pin
12
Manufacturer Specific
Not Implemented
13
Input Voltage/ Current/Power Fault
Not Implemented
14
Output Current/Power Fault
Not Implemented
15 (MSB)
Output Voltage Fault
VOUT outside PGOOD window
(Note 3)
Note 1: Communication failure is one of following faults: host sends too
few bits, host reads too few bits, host writes too few bytes, host reads too
many bytes, improper R/W bit set, unsupported command code, attempt
to write to a read-only command. See PMBus Specification v1.2, Part II,
Sections 10.8 and 10.9 for more information.
Note 2: Power may be off due to any one of the following conditions:
RUN_STBY low, OPERATION ON cleared, PVIN undervoltage or
overtemperature warning. When the power is off due to RUN_MSTR
low or due to a more serious fault conditions such as VIN low or
overtemperature fault, the PMBus interface is turned off instead of
asserting the OFF bit.
Note 3: This bit is disabled when drivers are off for any reason, soft-start
not complete, or the VOUT has not reached the PGOOD window for the first
time.
All of the following telemetry registers are initialized to
0x8000 when cycling power, cycling RUN_MSTR pin or
sending a MFR_RESET command. The register will remain
at this value until its first conversion is complete—typically within 50ms of the initialization event.
The output voltage is sensed at the VCC_SEN and VSS_
SEN pins.
READ_VIN
READ_IIN
The READ_VIN command returns the measured input
voltage, in volts, at the VIN pin.
This read-only command has two data bytes and is formatted as a 16-bit 2’s complement value scaled 4mV/bit.
READ_VOUT
The READ_VOUT command returns the measured output voltage, in volts as specified by the VOUT_MODE
command.
36
This read-only command has two data bytes and is formatted as a 16-bit 2’s complement value scaled 0.5mV/
bit.
The READ_IIN command returns the input current in
Amperes. The input current is derived from READ_IOUT
current and the measured duty cycle with an offset term
added to account for quiescent current and driver current.
For accurate values at light load currents the part must be
in continuous conduction mode.
This register is reset to 0x8000 is standby mode when
the drivers are off.
Rev B
For more information www.analog.com
LTC3815
PMBus COMMAND DETAILS
This read-only command has two data bytes and is formatted as a 16-bit 2’s complement value scaled 10mA/bit.
This command has two data bytes and is formatted as a
16-bit 2’s complement value scaled 4mV/bit.
READ_IOUT
MFR_TEMPERATURE_1_PEAK
The READ_IOUT command returns the average output
current in amperes. The LTC3815 senses and measures
the currents through its top and bottom power switches
to derive IOUT current. For accurate values at light load
currents the part must be in continuous conduction mode.
The MFR_TEMPERATURE_1_PEAK command reports the
highest temperature, in degrees Celsius, reported by the
READ_TEMPERATURE_1 measurement.
This register is reset to 0x8000 is standby mode when
the drivers are off.
This read-only command has two data bytes and is formatted as a 16-bit 2’s complement value scaled 10mA/bit.
READ_TEMPERATURE_1
The READ_TEMPERATURE_1 command returns the internal die temperature, in degrees Celsius, of the LTC3815.
This read-only command has two data bytes and is formatted as a 16-bit 2’s complement value scaled 1°C/bit.
MFR_VOUT_PEAK
The MFR_VOUT_PEAK command reports the highest voltage, in volts, reported by the READ_VOUT measurement.
To clear the peak value and restart the peak monitor, use
the MFR_CLEAR_PEAKS command or write to the MFR_
VOUT_PEAK. When writing to MFR_VOUT_PEAK, zero,
one or two data bytes are accepted but the data is ignored.
This command has two data bytes and is formatted as a
16-bit 2’s complement value scaled 0.5mV/bit.
MFR_VIN_PEAK
The MFR_VIN_PEAK command reports the highest voltage, in volts, reported by the READ_VIN measurement.
To clear the peak value and restart the peak monitor, use
the MFR_CLEAR_PEAKS command or write to the MFR_
VIN_PEAK. When writing to MFR_VIN_PEAK zero, one
or two data bytes are accepted but the data is ignored.
To clear the peak value and restart the peak monitor,
use the MFR_CLEAR_PEAKS command or write to the
MFR_TEMPERATURE_1_PEAK. When writing to MFR_
TEMPERATURE_1__PEAK zero, one or two data bytes
are accepted but the data is ignored.
This command has two data bytes and is formatted as a
16-bit 2’s complement value scaled 1°C/bit.
MFR_IOUT_PEAK
The MFR_IOUT_PEAK command reports the highest current, in amperes, reported by the READ_IOUT
measurement.
To clear the peak value and restart the peak monitor, use
the MFR_CLEAR_PEAKS command or write to the MFR_
IOUT_PEAK. When writing to MFR_IOUT_PEAK, zero, one
or two data bytes are accepted but the data is ignored.
This command has two data bytes and is formatted as a
16-bit 2’s complement value scaled 10mA/bit.
MFR_IIN_PEAK
The MFR_IIN_PEAK command reports the highest current, in amperes, reported by the READ_IIN measurement.
To clear the peak value and restart the peak monitor, use
the MFR_CLEAR_PEAKS command or write to the MFR_
IIN_PEAK. When writing to MFR_IIN_PEAK, zero, one or
two data bytes are accepted but the data is ignored.
This command has two data bytes and is formatted as a
16-bit 2’s complement value scaled 10mA/bit.
Rev B
For more information www.analog.com
37
LTC3815
TYPICAL APPLICATIONS
1.2V/6A 1MHz Buck Regulator with Minimum External Components
VIN
2.25V TO 5.5V
100k
10k
10k
10k
PVIN
PGOOD
MODE/SYNC
PGOOD
SCL
PMBus
CIN
22µF
×2
VIN
RUN_MSTR
LTC3815
SDA
RUN_STBY
ALERT
CLKOUT
PGFD
MARGIN
ASEL
0.33µH
TRACK/SS
SW
VCC_SENSE
CSLEW
COUT
100µF
×2
VSS_SENSE
RT
12k
0.5%
PGOOD DELAY: 190ms
PGOOD THRESHOLD ±10%
FREQUENCY: 1MHz
SOFT-START DELAY: 1ms
MARGIN SLEW RATE: 23%/ms
DCM MODE
PMBus ADDRESS: 0x20
1k
DAOUT
PGLIM
VOUT
1.2V
6A
VFB
REF
SGND PGND
ITH
WP
10k
1nF
47pF
3815 TA02
CIN: TAIYO YUDEN LMK316BJ226ML-T
COUT: MURATA GRM32ER60J107ME20
L: COILCRAFT XAL6030-331MEB
1.2V/6A 2MHz Buck Regulator
VIN
2.25V TO 5.5V
100k
10k
10k
10k
PGOOD
PVIN
MODE/SYNC
PGOOD
SCL
PMBus
LTC3815
SDA
64.9k
1%
22nF
46.4k
1%
RUN_MSTR
RUN_STBY
ALERT
CLKOUT
PGFD
MARGIN
ASEL
SW
TRACK/SS
100pF
VCC_SENSE
COUT
100µF
×2
VSS_SENSE
RT
11.8k, 1%
DAOUT
PGLIM
60.4k
0.5%
1k
VOUT
1.2V
6A
VFB
REF
SGND PGND
WP
ITH
10k
47pF
CIN: TAIYO YUDEN LMK316BJ226ML-T
COUT: MURATA GRM32ER60J107ME20
L: COILCRAFT XAL6030-181MEB
38
PGOOD DELAY: 1.6ms
PGOOD THRESHOLD ±20%
FREQUENCY: 2MHz
SOFT-START DELAY: 5ms
MARGIN SLEW RATE: 1%/ms
DCM MODE
PMBus ADDRESS: 0x22
0.18µH
CSLEW
59.7k
0.5%
CIN
22µF
×2
VIN
1nF
3815 TA03
Rev B
For more information www.analog.com
LTC3815
TYPICAL APPLICATIONS
12V Input, 1.0V/6A Output Buck Regulator
C1
2.2µF
0.1µF
D1
10Ω
23
24
1
2
16.2k
3
4
5
12k
6
330pF
10pF
0.1µF
20
PVIN
PHMODE
PVIN
MODE
18
TRACK/SS
SW
ITH
15
PGOOD
10k
PGOOD
VON
PGND
9
10
8
SW
3.3V
22.6k
COUT
47µF
×2
13
SW
11
100k
PGND
10k
PVIN
SGND
PGOOD DELAY: 190ms
PGOOD THRESHOLD ±10%
FREQUENCY: 1MHz
SOFT-START DELAY: 1ms
MARGIN SLEW RATE: 23%/ms
DCM MODE
PMBus ADDRESS: 0x20
VIN
MODE/SYNC
SCL
LTC3815
SDA
RUN_MSTR
RUN_STBY
ALERT
CLKOUT
PGFD
MARGIN
ASEL
0.33µH
TRACK/SS
SW
VCC_SENSE
CSLEW
10k
0.5%
4.99k
12
PGOOD
PMBus
L1 0.68µH
14
SW
RUN
C1: AVX 0805ZD225MAT2A
CIN: TDK C4532X5RIC226M
COUT: TDK C3216X5ROJ476M
D1: CENTRAL SEMI CMDSH-3
L1: VISHAY IHLP-2525CZERR68-M01
16
LTC3605
SW
0.1µF
17
SW
FB
VIN
4V TO 15V
CIN
22µF
×2
19
RT
7
10k
21
CLKIN CLKOUT SGND INTVCC BOOST SVIN
SVIN
100k
22
COUT
100µF
×2
VSS_SENSE
RT
DAOUT
PGLIM
1k
VOUT
1.0V
6A
VFB
REF
SGND PGND
WP
ITH
10k
1nF
47pF
CIN: TAIYO YUDEN LMK316BJ226ML-T
COUT: MURATA GRM32ER60J107ME20
L: COILCRAFT XAL6030-331MEB
3815 TA04
Rev B
For more information www.analog.com
39
LTC3815
PACKAGE DESCRIPTION
UFE Package
38-Lead Plastic QFN (4mm × 6mm)
(Reference LTC DWG # 05-08-1750 Rev B)
0.70 ±0.05
4.50 ±0.05
3.10 ±0.05
2.40 REF
2.65 ±0.05
4.65 ±0.05
PACKAGE OUTLINE
0.20 ±0.05
0.40 BSC
4.40 REF
5.10 ±0.05
6.50 ±0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
4.00 ±0.10
0.75 ±0.05
R = 0.10
TYP
PIN 1 NOTCH
R = 0.30 OR
0.35 × 45°
CHAMFER
2.40 REF
37
38
0.40 ±0.10
PIN 1
TOP MARK
(NOTE 6)
1
2
4.65 ±0.10
6.00 ±0.10
4.40 REF
2.65 ±0.10
(UFE38) QFN 0708 REV B
0.200 REF
0.00 – 0.05
R = 0.115
TYP
0.20 ±0.05
0.40 BSC
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
40
Rev B
For more information www.analog.com
LTC3815
REVISION HISTORY
REV
DATE
DESCRIPTION
A
03/16
Changed VIN_TUE from ±1% to ±1.5%
PAGE NUMBER
4
B
06/18
Changed title to include “PMBus Interface”
1
Rev B
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license For
is granted
implication or
otherwise under any patent or patent rights of Analog Devices.
more by
information
www.analog.com
41
LTC3815
TYPICAL APPLICATION
1.2V/12A 2-Phase Buck Regulator
MASTER
SLAVE
VIN
2.25V TO 5.5V
PVIN
100k
PGOOD
PMBUS
VOUT
1.2V, 12A
VIN
CLKOUT
MODE/SYNC
PGLIM
PGOOD
RUN_MSTR
RUN_MSTR
MODE/SYNC
LTC3815
RUN_STBY
SW
SCL, SDA, ALERT
RUN_STBY
L1, 0.5µH
COUT
100µF
×2
VSS_SENSE
MARGIN
MODE/SYNC
DAOUT
PGFD
ASEL
VFB
CSLEW
1nF
RT
SGND PGND
L2
0.5µH
SW
10k
VSS_SENSE
MARGIN
PGOOD
ASEL
CSLEW
ITH
ITH
REF
12k
0.5%
PGFD
VFB
1nF
PMBUS
SCL, SDA, ALERT
VCC_SENSE
REF
TRACK/SS
WP
LTC3815
DAOUT
1k
CIN
22µF
×2
VIN
PGLIM
VCC_SENSE
24.9k
PVIN
22nF
TRACK/SS
SGND PGND
RT
24.9k 1nF
CLKOUT
WP
3815 TA04
CIN: TAIYO YUDEN LMK316BJ226ML-T
COUT: MURATA GRM32ER60J107ME20
L1, L2: COILCRAFT XAL6030-331MEB
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4.5V ≤ VIN ≤ 38V, VOUT Up to 5.5V, Very High Output Current,
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42
4.5V ≤ VIN ≤ 24V, 0.5V ≤ VOUT0 (±0.5%) ≤ 5.4V, 145ms Start-Up,
I2C/PMBus Interface with EEPROM and 16-Bit ADC
Rev B
D16955-0-6/18(B)
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For more information www.analog.com
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