DICE/DWF SPECIFICATION
RH3845MK
High Voltage Synchronous
Step-Down Controller
DESCRIPTION
The RH3845MK is a high voltage, synchronous, current
mode controller for medium to high power, high efficiency
supplies. It offers a wide 4V to 60V input range (7.5V
minimum start-up voltage). An onboard regulator sim-
plifies the biasing requirements by providing IC power
directly from V
IN
.
Additional features include an adjustable fixed operating
frequency synchronizable to an external clock for noise
sensitive applications, gate drivers capable of driving large
N-channel MOSFETs, a precision undervoltage lockout,
low shutdown current, short-circuit protection, and a
programmable soft-start.
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN
............................................................................65V
BOOST ......................................................................80V
BOOST to SW............................................................24V
V
CC
, MODE ................................................................24V
SENSE
+
, SENSE
–
.......................................................40V
SENSE
+
TO SENSE
–
..................................................±1V
SYNC, V
FB
, AND C
SS
...................................................5V
SHDN
Pin Current ....................................................1mA
Operating Junction Temperature Range ...–55°C to 125°C
Storage Temperature Range................... –65°C to 150°C
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
DICE PINOUT
20
1
PAD FUNCTION
19
DIE CROSS REFERENCE
LTC
®
Finished
Part Number
RH3845MK
RH3845MK
Order
Part Number
RH3845MK DICE
RH3845MK DWF*
18
2
17
16
3
4
15
5
14
6
7
13
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
V
IN
SHDN
C
SS
MODE
V
FB
V
C
SYNC
f
SET
GND
GND
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
GND
SENSE
–
SENSE
+
PGND
BG
V
CC
SW
TG
BOOST
GND
Please refer to LTC standard product data sheet for
other applicable product information.
*DWF = DICE in wafer form.
8
9
10
11
12
113mils
×
124mils,
Backside Metal: Alloyed Gold Layer
Backside Potential: GND
1
DICE/DWF SPECIFICATION
TABLE 1: DICE/DWF ELECTRICAL TEST LIMITS
PARAMETER
V
IN
Minimum Start Voltage (Note 2)
V
IN
UVLO Threshold (Falling)
V
IN
Supply Current
V
IN
Shutdown Current
BOOST Supply Current (Note 3)
V
CC
Supply Current
V
CC
Current Limit
SHDN
Enable Threshold (Rising)
SHDN
Hysteresis
Reference Voltage
V
FB
Input Bias Current
V
FB
Error Amp Transconductance
Error Amp Sink/Source Current
MODE Pin Current (Note 4)
Peak Current Limit Sense Voltage
Soft-Start Charge Current
Sense Pins Common-Mode Range
Sense Pins Input Current
Reverse Protect Sense Voltage
Reverse Current Sense Voltage Offset
Switching Frequency
Programmable Frequency Range
V
SENSE(CM)
> 4V
V
MODE
= 7.5V
V
MODE
= V
FB
R
T
= 49.9k
270
100
80
8
0
350
35
2
120
14
36
400
120
12
350
500
–40
1.30
100
1.214
1.4
150
1.250
50
V
CC
> 9V
V
SHDN
= 0.3V
3.6
CONDITIONS
T
A
= 25°C
MIN
MAX
7.5
4.0
200
100
2
4.5
UNITS
V
V
μA
μA
mA
mA
mA
V
mV
V
nA
μS
μA
μA
mV
μA
V
μA
mV
mV
kHz
kHz
2
DICE/DWF SPECIFICATION
TABLE 2: ELECTRICAL CHARACTERISTICS
PARAMETER
V
IN
Minimum Start Voltage (Note 2)
V
IN
UVLO Threshold (Falling)
V
IN
Supply Current
V
IN
Shutdown Current
BOOST Supply Current (Note 3)
V
CC
Supply Current
V
CC
Current Limit
SHDN
Enable Threshold (Rising)
SHDN
Hysteresis
Reference Voltage
V
FB
Input Bias Current
V
FB
Error Amp Transconductance
Error Amp Sink/Source Current
Peak Current Limit Sense Voltage
Soft-Start Charge Current
Sense Pins Common-Mode Range
Sense Pins Input Current
Reverse Protect Sense Voltage
Switching Frequency
Programmable Frequency Range
External Sync Frequency Range
SYNC Voltage Threshold
Non-Overlap Time TG to BG
Non-Overlap Time BG to TG
TG Minimum On-Time
TG Minimum Off-Time
TG, BG Drive On Voltage
TG, BG Drive Off Voltage
TG, BG Drive Rise Time
TG, BG Drive Fall Time
C
TG
= C
BG
= 3300pF
C
TG
= C
BG
= 3300pF
V
CC
= 10V
V
SENSE(CM)
> 4V
V
MODE
= 7.5V
R
T
= 49.9k
V
CC
> 9V
V
SHDN
= 0.3V
CONDITIONS
SUB-
GROUP
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
45
45
8
250
250
400
300
8.75
0.1
270
100
100
350
35
90
8
0
320
108
7
310
–40
1.30
100
1.214
3.6
3.8
130
65
1.4
3.8
–150
1.38
140
1.232
20
450
50
105
12
120
16
36
400
120
20
350
500
600
2
1.5
150
1.250
50
MIN
(Pre-Irradiation)
MAX
7.5
4.0
200
100
2
4.5
SUB-
GROUP
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
8
0.1
270
100
100
340
20
85
8
0
125
16
36
500
140
25
350
500
600
2
–40
1.30
100
1.214
20
540
1.5
180
1.250
3.6
3.8
–55°C ≤ T
A
≥ 125°C
MIN
TYP
MAX
7.5
4.0
800
200
3.5
4.5
UNITS
V
V
μA
μA
mA
mA
mA
V
mV
V
nA
μS
μA
mV
μA
V
μA
mV
mV
kHz
kHz
kHz
V
ns
ns
ns
ns
V
V
ns
ns
T
A
= 25°C
TYP
Reverse Current Sense Voltage Offset V
MODE
= V
FB
3
DICE/DWF SPECIFICATION
TABLE 3: ELECTRICAL CHARACTERISTICS
PARAMETER
V
IN
Minimum Start Voltage (Note 2)
V
IN
UVLO Threshold (Falling)
V
IN
Supply Current
V
IN
Shutdown Current
BOOST Supply Current (Note 3)
V
CC
Supply Current
V
CC
Current Limit
SHDN
Enable Threshold (Rising)
SHDN
Hysteresis
Reference Voltage
V
FB
Input Bias Current
V
FB
Error Amp Transconductance
Error Amp Sink/Source Current
Peak Current Limit Sense Voltage
Soft-Start Charge Current
Sense Pins Common-Mode Range
Sense Pins Input Current
Reverse Protect Sense Voltage
Reverse Current Sense Voltage Offset
Switching Frequency
Programmable Frequency Range
Non-Overlap Time TG to BG
Non-Overlap Time BG to TG
TG Minimum On-Time
TG Minimum Off-Time
TG, BG Drive On Voltage
TG, BG Drive Off Voltage
TG, BG Drive Rise Time
TG, BG Drive Fall Time
CONDITIONS
7.5
4
200
100
2
4.5
(Post-Irradiation)
UNITS
V
V
μA
μA
mA
mA
mA
V
mV
V
nA
μS
μA
mV
μA
V
μA
mV
mV
kHz
kHz
ns
ns
ns
ns
V
V
ns
ns
10KRADS (Si) 20KRADS (Si) 50KRADS (Si) 100KRADS (Si) 200KRADS (Si)
MIN MAX MIN MAX MIN MAX MIN
MAX
MIN
MAX
7.5
4
200
100
2
4.5
7.5
4
200
100
2
4.5
–40
1.30
100
1.204
280
35
80
5
7.5
4
200
100
2
4.5
1.5
180
1.240
250
–40
1.30
80
1.187
250
30
75
4
7.5
4
200
100
2
4.5
1.5
180
1.223
350
V
CC
> 9V
V
SHDN
= 0.3V
–40
1.30
1.5
100
180
1.214 1.250
50
350
35
90
120
8
16
36
400
V
SENSE(CM)
> 4V
120
V
MODE
= 7.5V
10
V
MODE
= V
FB
270
350
R
T
= 49.9k
100
500
350
350
500
350
8
V
CC
= 10V
0.1
60
C
TG
= C
BG
= 3300pF
60
C
TG
= C
BG
= 3300pF
–40
–40
1.30
1.5
1.30
1.5
100
180
100
180
1.210 1.246 1.208 1.244
100
120
330
300
35
35
85
120
85
120
8
16
6
16
36
36
400
400
120
120
10
10
270
350
270
350
100
500
100
500
350
350
350
350
500
500
350
350
8
8
0.1
0.1
60
60
60
60
270
100
120
16
36
400
120
10
350
500
350
350
500
360
0.1
60
60
270
100
120
16
36
400
120
10
350
500
350
350
500
360
0.1
60
60
8
8
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.
Note 2:
V
IN
voltages below the start-up threshold (7.5V) are only
supported when the V
CC
is externally driven above 6.5V.
Note 3:
Supply current specification does not include switch drive
currents. Actual supply currents will be higher.
Note 4:
Connect the MODE pin to V
FB
for pulse-skipping mode or V
CC
for forced continuous mode.
TABLE 4: ELECTRICAL TEST REQUIREMENTS
MIL-STD-883 TEST REQUIREMENTS
Final Electrical Test Requirements (Method 5004)
Group A Test Requirements (Method 5005)
Group B and D for Class S,
End Point Electrical Parameters (Method 5005)
*PDA applies to subgroup 1. See PDA Test Notes.
SUBGROUP
1*, 2, 3
1, 2, 3
1, 2, 3
PDA Test Notes
The PDA is specified as 5% based on failures from Group A, Subgroup 1,
tests after cooldown as the final electrical test in accordance with method
5004 of MIL-STD-883. The verified failures of Group A, Subgroup 1, after
burn-in divided by the total number of devices submitted for burn-in in that
lot shall be used to determine the percent for the lot.
Linear Technology Corporation reserves the right to test to tighter limits
than those given.
4
DICE/DWF SPECIFICATION
TOTAL DOSE BIAS CIRCUIT — RUN MODE
R5
1k
R1
4.99k
3V
R2
8.82k
0.1μF
V
IN
SHDN
C
SS
BOOST
R6 200k
TG
SW
R7 200k
20V
R10
750Ω
10V
R11
1.24k
R8
750Ω
30V
R9
750Ω
0.1μF
R3
1k
V
CC
MODE
RH3845MK
V
FB
BG
V
C
SYNC
PGND
SENSE
+
SENSE
–
GND
+
–
5V
R4
49.9k
f
SET
+
–
40V
RH3845MK RUN MODE
TOTAL DOSE BIAS CIRCUIT — SHUTDOWN MODE
R4
1k
V
IN
R1
2k
2.5V
R2
2.49k
0.1μF
SHDN
C
SS
BOOST
R5 200k
TG
SW
R6 200k
20V
R9
10k
10V
R10
10k
0.1μF
R7
10k
30V
R8
10k
V
CC
MODE
RH3845MK
V
FB
BG
V
C
SYNC
f
SET
R3
49.9k
GND
PGND
SENSE
+
SENSE
–
+
–
5V
+
–
40V
RH3845MK SHDN MODE
BURN-IN CIRCUIT — RUN MODE
1k
1k
1W
100Ω
V
IN
SHDN
4.87k
C
SS
GND
BOOST
200k
TG
10V
1W
10V
1W
10V
1W
10V
1W
10V
1W
10V
1W
SW
MODE
RH3845MK
V
CC
V
FB
V
C
SYNC
f
SET
BG
PGND
SENSE
+
SENSE
–
GND
499k
1k
200k
+
–
3.3V
1k
GND
GND
+
–
70V
1μF
150V
10μF
10V
RH3845MK BURN IN-RUN
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
5
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