...................................................... –0.3V to 40V
TEMP, FREQ, EXT_REF, V
FB
.................. –0.3V to INTV
CC
HYS_PRGM, I
TH
, RUN, TRACK/SS ....... –0.3V to INTV
CC
FAULT,
PGOOD ........................................... –0.3V to 80V
TIMER, MODE/PLLIN ............................ –0.3V to INTV
CC
INTV
CC
Peak Output Current ................................100mA
Operating Junction Temperature Range
(Notes 2, 3, 9) .................................... –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
32 31 30 29 28 27 26 25
UH PACKAGE
32-LEAD (5mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 44°C/W,
θ
JC
= 7.3°C/W
EXPOSED PAD (PIN 33) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC7821EUH#PBF
LTC7821IUH#PBF
TAPE AND REEL
LTC7821EUH#TRPBF
LTC7821IUH#TRPBF
http://www.linear.com/product/LTC7821#orderinfo
PART MARKING*
7821
7821
PACKAGE DESCRIPTION
32-Lead (5mm × 5mm) Plastic QFN
32-Lead (5mm × 5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°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.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
Rev A
2
For more information
www.analog.com
LTC7821
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= V
IN_SENSE
= 48V, V
RUN
= 5V, EXTV
CC
= 9V,
EXT_REF = 5.6V unless otherwise noted.
SYMBOL
V
IN
PARAMETER
Input Voltage Range
Output Voltage Range
V
FB
I
FB
V
REFLNREG
V
LOADREG
g
m
I
VIN
Regulated Feedback Voltage
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
(Note 4)
I
TH
Voltage (Note 5)
(Note 5)
V
IN
= 36V to 72V (Note 5)
(Note 5)
ΔI
TH
Voltage = 1.2V to 0.7V
ΔI
TH
Voltage = 1.2V to 1.6V
I
TH
= 1.2V; Sink/Source 5µA (Note 5)
(Note 6)
V
RUN
= 0V, EXTV
CC
= 0V
V
IN
= 20V, V
MID
= V
MID_SENSE
= 9V,
V
SW1
= 15V, V
SW3
= 10V
V
IN
= 48V, V
MID
= V
MID_SENSE
= 20V,
V
SW1
≥ 36V, V
SW3
= 12V
(Note 6)
V
RUN
= 0V
(Note 6)
l
l
l
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
10
0.9
0.792
TYP
MAX
72
V
IN
2
– 2.5
UNITS
V
V
V
nA
%/V
%
%
mmho
mA
µA
mA
mA
Main Control Loops
0.8
±10
0.003
0.016
–0.016
2
0.5
240
40
84
0.808
±50
0.02
0.1
–0.1
Transconductance Amplifier g
m
Input DC Supply Current
Normal Mode
Shutdown
Precharging Phase
I
VIN_SENSE
I
EXTVCC
I
MID
I
MID_SENSE
V
UVLO
V
UVLO_HYST
V
SENSE
I
SNS
+/-
I
TRACK/SS
V
RUN_ON
I
RUN
V
RUN_HYST
V
EXT_REF_UC
V
EXT_REF_LC
V
SEL_EXT_REF
I
EXT_REF
V
TEMP_TRIP
V
TEMP_TRIP_HYST
I
TEMP
V
BSTUVLO
V
BSTUVLO_HYST
T
OUT
Input DC Supply Current
Normal Mode
Shutdown
Input DC Supply Current
MID Pin Current
MID_SENSE Pin Current
V
IN
Undervoltage Lockout
UVLO Hysteresis
Current Sense Threshold
ISNS
+
and ISNS
–
Pin Current
Soft-Start Charge Current
RUN Pin On Threshold
RUN Pin Current
RUN Pin Hysteresis
EXT_REF Upper Clamp Limit
EXT_REF Lower Clamp Limit
EXT_REF De-Select Threshold (Ramping Up)
EXT_REF Pin Current
TEMP Pin Trip Point, Rising
TEMP Pin Trip Point Hysteresis
TEMP Pin Current
Undervoltage Lockout of (BOOST1-SW1),
(BOOST2- V
MID
) and (BOOST3-SW3)
Bootstrap Undervoltage Lockout Hysteresis
TEMP Trip TimeOut
1
45
2.2
45
4
mA
µA
mA
μA
μA
9.4
55
1.2
–11
1.6
V
V
mV
μA
μA
V
μA
V
V
0.45
V
V
nA
1.25
V
mV
nA
V
V
ms
V
IN
Ramping Up
V
ISNS–
= 0V
V
ISNS+
= V
ISNS–
= 12V
V
TRACK/SS
= 0V
V
RUN
Rising
V
RUN
= 0V
(Note 5)
(Note 5)
V
EXT_REF
= 0.6V
l
8.8
0.28
45
–9
50
–10
1.3
1
0.1
l
l
l
1.1
l
l
0.85
0.9
0.40
1.3
–150
l
1.22
100
1
4.4
1.4
100
V
TEMP
= 1V
Difference Voltage, Rising
Rev A
For more information
www.analog.com
3
LTC7821
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= V
IN_SENSE
= 48V, V
RUN
= 5V, EXTV
CC
= 9V,
EXT_REF = 5.6V unless otherwise noted.
SYMBOL
V
INTVCC
V
LDOINT
V
EXTVCC
V
EXTVCC_HYS
V
LDOEXT
f
NOM
f
LOW
f
HIGH
f
SYNC_LOW
f
SYNC_HIGH
I
FREQ
R
MODE/PLLIN
CLKOUT
HIGH
CLKOUT
LOW
PGOOD Output
V
PG1
PGOOD 1st Trip Level (with Delay)
V
FB
with Respect to Regulated Voltage
V
FB
Ramping Up (Overvoltage 1st Level)
V
FB
Ramping Down (Undervoltage 1st
Level)
V
FB
with Respect to Regulated Voltage
V
FB
Ramping Up (Overvoltage 2nd Level)
V
FB
Ramping Down (Undervoltage 2nd
Level)
I
PGOOD
= 0.6mA
V
PGOOD
= 80V
0.5
1.25
V
TIMER
= 0.9V
V
TIMER
= 2.8V
V
HYS_PRGM
= 0V
V
HYS_PRGM
= 1.2V
V
HYS_PRGM
= INTV
CC
V
HYS_PRGM
= 0V
I
FAULT
= 0.6mA
V
FAULT
= 80V
l
l
l
ELECTRICAL CHARACTERISTICS
PARAMETER
Internal V
CC
Regulator
INTV
CC
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Switchover Voltage Hysteresis
EXTV
CC
Load Regulation
Nominal Frequency
Lowest Frequency
Highest Frequency
Lowest Synchronizing Frequency
Highest Synchronizing Frequency
Frequency Setting Current
MODE/PLLIN Resistance
CLKOUT High Amplitude
CLKOUT Low Amplitude
CONDITIONS
10V < V
IN
< 72V, V
EXTVCC
= 0V
I
CC
= 1mA to 50mA, V
IN
= 12V, V
EXTVCC
= 0V
EXTV
CC
Ramping Positive, I
CC
= 1mA
V
EXTVCC
= 12V, I
CC
= 1mA to 50mA
R
FREQ
= 68kΩ
V
FREQ
= 0V
V
FREQ
= INTV
CC
MIN
5.65
TYP
5.8
–0.6
7
200
–0.6
MAX
5.95
–2
UNITS
V
%
V
mV
INTV
CC
Linear Regulator
–2
550
100
2000
1500
%
kHz
kHz
kHz
kHz
KHz
µA
kΩ
V
V
Oscillator and Phase Lock Loop
440
20
1400
200
V
FREQ
= 0V
l
490
50
1700
–9
–10
250
2.4
0
–11
6
–5.5
8.5
–7.5
15
15
–25
15
0.4
11
–9.5
%
%
mV
%
%
mV
V
PG1_HYST
V
PG2
PGOOD 1st Trip Level Hysteresis (with Delay)
PGOOD 2nd Trip Level
V
PG2_HYST
V
PGL
I
PGOOD
V
TIMER_LOW
V
TIMER_HIGH
I
TIMER
V
HYS_PRGM
I
HYS_PRGM
V
FAULT
I
FAULT
PGOOD 2nd Trip Level Hysteresis
PGOOD Voltage Low
PGOOD Leakage Current
Voltage At TIMER Pin To Start Capacitor
Balancing
Voltage At TIMER Pin To Stop Capacitor
Balancing
TIMER Pin Charge Current
Capacitor Balancing Window Comparator
Threshold
HYS_PRGM Pin Current
FAULT
Pin Voltage Low
FAULT
Leakage Current
–6
–3
0.5
1
V
μA
V
V
Capacitor Balancing
–7
–3.5
±0.3
±1.2
±0.8
–8
–4
µA
µA
V
V
V
–9
–10
0.2
–11
0.4
1
μA
V
μA
Rev A
4
For more information
www.analog.com
LTC7821
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= V
IN_SENSE
= 48V, V
RUN
= 5V, EXTV
CC
= 9V,
EXT_REF = 5.6V unless otherwise noted.
SYMBOL
I
FLYSRC1
I
FLYSNK1
I
FLYSNK3
I
FLYSRC3
I
MID_SRC
I
MID_SNK
Gate Driver
TG1,2
BG1, 2
TG1,2 t
r
TG1,2 t
f
BG1,2 t
r
BG1,2 t
f
T
1D
T
2D
T
3D
T
4D
T
5D
T
6D
t
on(MIN)
Pull-Up ON Resistance
Pull-Down ON Resistance
Pull-Up ON Resistance
Pull-Down ON Resistance
TG1, TG2 Transition Time:
Rise Time
Fall Time
BG1, BG2 Transition Time:
Rise Time
Fall Time
TG1 Off to BG1 On
TG2 Off to BG2 On
TG1 Off to TG2 Off
BG1 Off to TG1 On
BG2 Off to TG2 On
BG1 Off to BG2 Off
Minimum On-Time
(Note 8)
(Note 7)
2
1
2
1
4
4
4
4
45
20
25
40
20
20
210
Ω
Ω
Ω
Ω
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
PARAMETER
Current Out of SW1 During Capacitor
Balancing
CONDITIONS
(V
SW1
– V
SW3
) < V
IN
/2, V
SW3
= 12V
MIN
TYP
40
6
40
6
60
40
MAX
UNITS
mA
mA
mA
mA
mA
mA
ELECTRICAL CHARACTERISTICS
Current into SW1 During Capacitor Balancing (V
SW1
– V
SW3
) > V
IN
/2, V
SW3
= 12V
Current into SW3 During Capacitor Balancing (V
SW1
– V
SW3
) < V
IN
/2, V
SW3
= 12V
Current Out of SW3 During Capacitor
Balancing
Current Out of MID During Capacitor
Balancing
(V
SW1
– V
SW3
) < V
IN
/2, V
SW3
= 12V
V
MID
< V
IN
/2, V
MID
= V
MID_SENSE
= 20V
V
SW1
≥ 36V, V
SW3
= 12V
Current into MID During Capacitor Balancing V
MID
> V
IN
/2, V
MID
= V
MID_SENSE
= 28V
V
SW1
≥ 36V, V
SW3
= 12V
(Note 7)
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 LTC7821E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC7821I is guaranteed
to meet performance specifications over the full –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:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC7821UH:
T
J
= T
A
+ (P
D
• 44°C/W)
Note 4:
Output voltage range is guaranteed by design. For output voltage
setting, read “Output Voltage Setting” and “Minimum V
OUT
” in the
“Applications Information” section.
Note 5:
The LTC7821 is tested in a feedback loop that servos V
ITH
to a
specified voltage and measures the resultant V
FB
.
Note 6:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 7:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 8:
The minimum on-time condition is specified for an inductor
peak-to-peak ripple current ≥ 40% of I
MAX
(see Minimum On-Time
Considerations in the Applications Information section)
Note 9:
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.
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