TECHNICAL NOTE
High-performance Regulator IC Series for PCs
Termination Regulators
for DDR-SDRAMs
BD3537F
Description
BD3537F is a termination regulator compatible with JEDEC DDR-SDRAM, which functions as a linear power supply
incorporating an N-channel MOSFET and provides a sink/source current capability up to 1.8A respectively. A built-in
high-speed OP-AMP specially designed offers an excellent transient response. Requires 5.0 volts as a bias power supply
to drive the N-channel MOSFET. For BD3537F, ceramic capacitor can be used as output capacitor. Thus, the BD3537F
is designed to enable significant package profile downsizing as the total regulator part.
Features
1) Incorporates a push-pull power supply for termination (VTT)
2) Incorporates an enabler
3) Incorporates an undervoltage lockout (UVLO)
4) Employs SOP8 package
5) Incorporates a thermal shutdown protector (TSD)
6) Compatible with Dual Channel (DDR-II)
7) Operates with input voltage from 4.75 to 5.25 volts
8) Incorporates soft start function
Use
Power supply for DDR I/II - SDRAM
Oct. 2008
●ABSOLUTE MAXIMUM RATINGS
Parameter
Symbol
Limits
Unit
VCC
7 *1
V
REF
*1
V
7 *1
V
Input Voltage
REF Input Voltage
Termination Input Voltage
7
VTT_IN
Output Current
ITT
3
A
Power Dissipation1
Pd1
560 *2
mW
Power Dissipation2
Pd2
690 *3
mW
Operating Temperature Range
Topr
-30~+100
℃
Storage Temperature Range
Tstg
-55~+150
℃
Tjmax
+150
℃
Maximum Junction Temperature
*1 Should not exceed Pd.
*2 Reduced by 4.48mW for each increase in Ta of 1℃ over 25℃ (no heat sink).
*3 Reduced by 5.52mW for each increase in Ta of 1℃ over 25℃ (when mounted on 70mm x 70mm x 1.6mm Glass-epoxy PCB).
●OPERATING CONDITIONS (Ta=25℃)
Parameter
Input Voltage
Termination Input Voltage
Reference Voltage
Symbol
MIN
MAX
Unit
VCC
4.75
5.25
V
VTT_IN
1.746
1.854
V
VEN
0.6
1.6
V
★ No radiation-resistant design is adopted for the present product.
●ELECTRICAL CHARACTERISTICS (unless otherwise noted, Ta=25℃, VCC=5V, REF=0.9V, VTT_IN=1.8V)
Standard Value
Parameter
Symbol
Unit
Condition
MIN
TYP
MAX
Standby Current
IST
-
50
90
uA
REFTerminal A>Terminal B, or
・a parasitic transistor if the electric potentials at the terminals satisfy the following relationship; Terminal B>GND Terminal A.
The structure of the IC inevitably forms parasitic elements, the activation of which may cause interference among circuits,
and/or malfunctions contributing to breakdown. It is therefore requested to take care not to use the device in such manner
that the voltage lower than GND (at P-substrate) may be applied to the input terminal, which may result in activation of
parasitic elements.
Resistor
Transistor (NPN)
Pin A
Pin B
C
Pin B
B
E
Pin A
N
P+
N
P+
P
N
N
Parasitic
element
P+
P substrate
Parasitic element
GND
B
N
P+
P
N
C
E
Parasitic
element
P substrate
Parasitic element
7/10
GND
GND
GND
Other adjacent elements
10. GND wiring pattern
When both a small-signal GND and high current GND are present, single-point grounding (at the set standard point) is
recommended, in order to separate the small-signal and high current patterns, and to be sure the voltage change stemming
from the wiring resistance and high current does not cause any voltage change in the small-signal GND. In the same way,
care must be taken to avoid wiring pattern fluctuations in any connected external component GND.
11. Output capacitor (C3)
Do not fail to connect a output capacitor to VTT output terminal for stabilization of output voltage. The capacitor connected to
VTT output terminal works as a loop gain phase compensator. Insufficient capacitance may cause an oscillation. It is
recommended to connect a 10 μF ceramic capacitor (X5R or X7R) near to VTT and GND, though it depends on ambient
temperature and other conditions. A low ESR ceramic capacitor may reduce a loop gain phase margin and may cause an
oscillation, which may be improved by connecting a resistor in series with the OS-capacitor (several-hundred μF). It is
therefore requested to carefully check under the actual temperature and load conditions to be applied.
12. Input capacitors (C1 and C2)
These input capacitors are used to reduce the output impedance of power supply to be connected to the input terminals (VCC
and VTT_IN). Increase in the power supply output impedance may result in oscillation or degradation in ripple rejecting
characteristics. It is recommended to use a low temperature coefficient 1μF (for VCC) and 10μF (for VTT_IN) capacitor, but it
depends on the characteristics of the power supply input, and the capacitance and impedance of the pc board wiring pattern.
It is therefore requested to carefully check under the actual temperature and load conditions to be applied.
13. Input terminals (VCC, VTT_IN and REF)
VCC, VTT_IN and REF terminals of this IC are made up independent one another. To VCC terminal, the UVLO function is
provided for malfunction protection. REF pin includes the Enable circuit. Irrespective of the input order of the inputs
terminals, VTT output is activated to provide the output voltage when UVLO voltages reach the threshold voltage while REF
voltage reaches the threshold of EN pin.
14.REF pin (R1 , R2 , C4)
REF pin controls this IC’s status ON or OFF. When REF voltage reaches EN-ON voltage, the output voltage operates. Then
BD3537F does not include “soft start function” so set the start up time by the value of extra components R1, R2 and C4.
15. Operating range
Within the operating range, the operation and function of the circuits are generally guaranteed at an ambient temperature
within the range specified. The values specified for electrical characteristics may not be guaranteed, but drastic change may
not occur to such characteristics within the operating range.
16. Allowable loss Pd
For the allowable loss, the thermal derating characteristics are shown in the Exhibit, which should be used as a guide. Any
uses that exceed the allowable loss may result in degradation in the functions inherent to IC including a decrease in current
capability due to chip temperature increase. Use within the allowable loss.
17. Built-in thermal shutdown protection circuit
Thermal shutdown protection circuit is built-in to prevent thermal breakdown. Turns VTT output to OFF when the thermal
shutdown protection circuit activates. This thermal shutdown protection circuit is originally intended to protect the IC itself.
It is therefore requested to conduct a thermal design not to exceed the temperature under which the thermal shutdown
protection circuit can work.
18. The use in the strong electromagnetic field may sometimes cause malfunction, to which care must be taken.
In the event that load containing a large inductance component is connected to the output terminal, and generation of
back-EMF at the start-up and when output is turned OFF is assumed, it is requested to insert a protection diode.
19. In the event that load containing a large inductance component is
(Example)
connected to the output terminal, and generation of back-EMF at the
OUTPUT PIN
start-up and when output is turned OFF is assumed, it is requested
to insert a protection diode.
20. We are certain that examples of applied circuit diagrams are recommendable,
but you are requested to thoroughly confirm the characteristics before using the IC.
In addition, when the IC is used with the external circuit changed, decide the IC with sufficient margin provided
while consideration is being given not only to static characteristics but also variations of external parts and our IC including
transient characteristics.
8/10
●POWER DISSIPATION
◎SOP8(BD3537F)
[mW]
700
Power Dissipation [Pd]
600
(1) 690mW
(1) 70mm×70mm×1.6mm Glass-epoxy PCB
θj-c=181℃/W
(2) With no heat sink
θj-a=222℃/W
500
(2) 560mW
400
100℃
300
200
100
0
0
25
50
75
100
125
150
[℃]
Ambient Temperature [Ta]
●Ordering part number
B
D
3
5
3
7
F
Package Type
Part Number
E
―
2
E2 Emboss tape reel Pin 1 opposite draw-out side
・F : SOP8
・BD3537
SOP8
1
4
1234
1234
1234
1Pin
1234
(Unit:mm)
1234
Reel
1234
1234
1.27
0.4±0.1
E2
(The direction is the 1pin of product is at the upper left when you hold
reel on the left hand and you pull out the tape on the right hand)
0.15±0.1
0.1
1234
1.5±0.1
0.11
6.2±0.3
4.4±0.2
0.3Min.
5
Embossed carrier tape
2500pcs
Direction
of feed
5.0±0.2
8
Tape
Quantity
Direction of feed
※When you order , please order in times the amount of package quantity.
9/10
10/10
Catalog No.08T425A '08.10 ROHM ©
Appendix
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Appendix1-Rev3.0