RICHTEK RT9996

RT9996
Power Management IC for SSD
General Description
Features
The RT9996 is a 2-CH PMIC for SSD (Solid-State Drive).
It integrates synchronous buck converters and one voltage
detector.
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The RT9996 provides 2 independent enable pins for
sequence control and auto discharge when powered off
on the power line of a NAND Flash.
The frequency can be up to 2MHz, allowing the use of
smaller sized inductors to meet the space and height limit
in handheld applications.
To maximize power utilization, the RT9996 is designed
with extremely low quiescent current. The buck converter
can consume down to 70μA when operating in standby
mode.
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Supply Input Voltage Range : 2.8V to 5.5V
Buck 1 / Buck 2
` Adjustable Output Voltage for VCORE or DRAM
Cache
` Output Current up to 1A
Voltage Detector
` Programmable Threshold Voltage
` Open-Drain Reset Output
RoHS Compliant and Halogen Free
Applications
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1.8/2.5 inch Solid-State Drives
Portable Devices
USB-Based Hand-Held Products
The RT9996 is available in a VQFN-32L 5x5 package.
Pin Configurations
Ordering Information
NC
NC
NC
NC
FB2
EN2
VIN
LX2
(TOP VIEW)
RT9996
Package Type
QV : VQFN-32L 5x5 (V-Type)
Note :
Richtek products are :
`
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
`
Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
RT9996GQV : Product Number
RT9996
GQV
YMDNN
1
24
2
23
3
22
4
5
21
GND
20
6
19
7
18
33
8
17
LX2
GND
GND
VIN
VIN
GND
GND
LX1
9 10 11 12 13 14 15 16
NC
RESET
VDET
GND
FB1
EN1
VIN
LX1
Lead Plating System
G : Green (Halogen Free and Pb Free)
32 31 30 29 28 27 26 25
NC
NC
NC
NC
NC
VIN
NC
NC
VQFN-32L 5x5
YMDNN : Date Code
DS9996-01 April 2011
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1
RT9996
Typical Application Circuit
RT9996
VIN
5V
6, 15, 20, 21, 26 VIN
LX1
16, 17
L1
2.2µH
C1
R1
30k
R7
FB1
11 VDET
C2
10µF
VOUT1
1.2V/1A
13
R2
64.9k
R8
VDD
3.3V
R9
43k
Chip Enable
10
LX2
RESET
24, 25
L2
2.2µH
R3
80k
14 EN1
27 EN2
FB2
C3
10µF
VOUT2
1.8V/1A
28
R4
64.9k
12, 18, 19, 22, 23,
33 (Exposed Pad) GND
Function Block Diagram
RESET
-
VDET
0.7V
+
VIN
EN1
Buck
Converter 1
LX1
FB1
VIN
EN2
GND
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2
Buck
Converter 2
LX2
FB2
DS9996-01 April 2011
RT9996
Functional Pin Description
Pin No.
1, 2, 3, 4, 5, 7, 8,
9, 29, 30, 31, 32
6, 15, 20, 21, 26
10
Pin Name
Pin Function
NC
No Internal Connection.
VIN
Buck Converter 1 and Buck Converter 2 Power Supply Input.
RESET
Reset Output.
11
VDET
12, 18, 19, 22, 23,
GND
33 (Exposed Pad)
13
FB1
Threshold Voltage Detect Setting.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Buck Converter 1 Feedback Input.
14
EN1
Buck Converter 1 Chip Enable (Active High).
16, 17
LX1
Buck Converter 1 Switch Output (inductor connection point).
24, 25
LX2
Buck Converter 2 Switch Output (inductor connection point).
27
EN2
Buck Converter 2 Chip Enable (Active High).
28
FB2
Buck Converter 2 Feedback Input.
DS9996-01 April 2011
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3
RT9996
Absolute Maximum Ratings
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z
z
z
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(Note 1)
Supply Input Voltage, VIN ----------------------------------------------------------------------------------------LX Pin Voltage ------------------------------------------------------------------------------------------------------Other Pins Voltage ------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
VQFN-32L 5x5 -----------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
VQFN-32L 5x5, θJA ------------------------------------------------------------------------------------------------VQFN-32L 5x5, θJC -----------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------Junction Temperature ---------------------------------------------------------------------------------------------Storage Temperature Range ------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Mode) --------------------------------------------------------------------------------------MM (Machine Mode) -----------------------------------------------------------------------------------------------
Recommended Operating Conditions
z
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–0.3V to 6.5V
–0.3V to (VIN + 0.3V)
–0.3V to 6.5V
2.778W
36°C/W
6°C/W
260°C
150°C
–65°C to 150°C
2kV
200V
(Note 4)
Supply Input Voltage, VIN ----------------------------------------------------------------------------------------- 2.8V to 5.5V
Junction Temperature Range ------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range ------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 5V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Buck Converter 1
Quiescent Current
IQ
No Load, No Switching
--
70
--
μA
Shutdown Current
ISHDN
EN = GND
--
0.2
--
μA
Feedback Reference Voltage
VFB
--
0.8
--
V
Adjustable Output Voltage
VOUT
VFB
--
VIN−0.2
V
--
0.05
--
%/V
--
0.5
--
%/A
VIN Rising
2.1
2.3
2.5
Hysteresis
0.1
0.2
0.3
Output Voltage Line Regulation
Output Voltage Load
Regulation
UVLO Under voltage Lockout
Threshold
VUVLO
V
Logic-High
VIH
1.5
--
VIN
Logic- Low
VIL
--
--
0.4
Peak Current Limit
ILIM
1.2
--
--
A
Oscillator Frequency
fOSC
1.2
1.5
1.8
MHz
--
250
--
μs
--
250
--
mΩ
--
260
--
mΩ
EN1 Threshold
Voltage
Start-Up Time
VIN = 3.6V, IOUT = 300mA
I OUT = 0mA. Time from active EN to
90% of VOUT
VIN = VGS = 3.6V, PWM Mode
P-MOSFET On-Resistance
RDS(ON)_P
N-MOSFET On-Resistance
RDS(ON)_N VIN = VGS = 3.6V, PWM Mode
V
To be continued
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DS9996-01 April 2011
RT9996
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Buck Converter 2
Quiescent Current
IQ
No Load, No Switching
--
70
--
μA
Shutdown Current
ISHDN
EN = GND
--
0.2
--
μA
Feedback Reference Voltage
VFB
0.784
0.8
0.816
V
Adjustable Output Voltage
VOUT
VFB
--
VIN−0.2
V
--
0.04
--
%/V
--
0.5
--
%/A
VIN Rising
--
2.1
--
Hysteresis
--
0.1
--
Output Voltage Line Regulation
Output Voltage Load
Regulation
UVLO Under voltage Lockout
threshold
VUVLO
V
Logic-High
VIH
1.5
--
VIN
V
Logic- Low
VIL
--
--
0.4
V
Peak Current Limit
I LIM
1.3
1.7
--
A
Oscillator Frequency
fOSC
VIN = 3.6V, IOUT = 300mA
1.2
1.5
1.8
MHz
--
250
--
μs
P-MOSFET On-Resistance
RDS(ON)_P
IOUT = 0mA Time from active EN to
90% of VOUT
VIN = VGS = 3.6V, PWM Mode
--
250
--
mΩ
N-MOSFET On-Resistance
RDS(ON)_N VIN = VGS = 3.6V, PWM Mode
--
260
--
mΩ
VIN Rising (L to H)
0.693
0.7
0.707
VIN Falling (H to L)
0.673
0.68
0.687
VDelay (L to H)
70
100
130
ms
VDelay (H to L)
5
10
20
μs
EN2 Threshold
Voltage
Start-Up Time
Voltage Detector
Voltage Detection Threshold
Voltage Detection Delay Time
V
Thermal Protections
Thermal Shutdown Threshold
TSD
--
160
--
°C
Thermal Shutdown Hysteresis
ΔTSD
--
25
--
°C
Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for
stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended
periods may remain possibility to affect device reliability.
Note 2. θJA is measured in natural convection at TA = 25°C on a high-effective thermal conductivity four-layer test board of
JEDEC 51-7 thermal measurement standard. The measurement case position of θJ is on the exposed pad of the
package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
DS9996-01 April 2011
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RT9996
Typical Operating Characteristics
Buck1 Output Accuracy vs. Load Current
Buck1 Efficiency vs. Load Current
100
Output Voltage Accuracy (%)
0.6%
0.6
Efficiency (%)
90
VIN1 = 2.8V
VIN1 = 3.6V
VIN1 = 4.2V
80
70
60
50
40
VBUCK1 = 1.2V
30
0.001
0.01
0.1
0.4%
0.4
0.2%
0.2
0
0.0%
-0.2
-0.2%
-0.4
-0.4%
-0.6
-0.6%
0.001
0.001
1
Output Voltage Accuracy (%)
Efficiency (%)
1
0.6%
0.6
90
VIN2 = 2.8V
VIN2 = 3.6V
VIN2 = 4.2V
70
60
50
40
VBUCK2 = 1.8V
0.01
0.1
1
0.4%
0.4
0.2
0.2%
0
0.0%
-0.2
-0.2%
-0.4
-0.4%
VBUCK2 = 1.8V, VIN2 = 5V
-0.6
-0.6%
0.001
0.001
0.01
0.1
Load Current (A)
Load Current (V)
Buck1 Output Ripple
Buck2 Output Ripple
VLX1
(5V/Div)
VLX2
(5V/Div)
VOUT1
(20mV/Div)
VOUT2
(20mV/Div)
ILX1
(1A/Div)
ILX2
(1A/Div)
VIN1 = 5V, ILOAD = 1A
Time (500ns/Div)
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0.1
Buck2 Output Accuracy vs. Load Current
Buck2 Efficiency vs. Load Current
100
30
0.001
0.01
Load Current (A)
Load Current (A)
80
VBUCK1 = 1.2V, VIN1 = 5V
1
VIN2 = 5V, ILOAD = 1A
Time (500ns/Div)
DS9996-01 April 2011
RT9996
Buck1 Load Transient Response
VBUCK1
(100mV/Div)
IOUT
(200mA/Div)
VBUCK2
(100mV/Div)
ILOAD = 40mA to 0.7A
Time (50μs/Div)
DS9996-01 April 2011
Buck2 Load Transient Response
IOUT
(200mA/Div)
ILOAD = 40mA to 0.7A
Time (50μs/Div)
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RT9996
Application Information
The basic RT9996 application circuit is shown in the section
Typical Application Circuit. External component selection
is determined by the maximum load current and begins
with the selection of the inductor value and operating
frequency followed by CIN and COUT.
loop is stable. Loop stability can be checked by viewing
the load transient response as described in a later section.
Inductor Selection
The output ripple is the highest at the maximum input
voltage since ΔIL increases with input voltage. Multiple
capacitors placed in parallel may be needed to meet the
ESR and RMS current handling requirements. Dry
tantalum, special polymer, aluminum electrolytic and
ceramic capacitors are all available in surface mount
packages. Special polymer capacitors offer very low ESR,
but have lower capacitance density than other types.
Tantalum capacitors have the highest capacitance density,
but it is important to only use types that have been surge
tested for use in switching power supplies. Aluminum
electrolytic capacitors have significantly higher ESR, but
can be used in cost-sensitive applications provided that
consideration is given to ripple current ratings and long
term reliability. Ceramic capacitors have excellent low ESR
characteristics but can have a high voltage coefficient and
audible piezoelectric effects. The high Q of ceramic
capacitors with trace inductance can also lead to significant
ringing.
For a given input and output voltage, the inductor value
and operating frequency determine the ripple current. The
ripple current ΔIL increases with higher VIN and decreases
with higher inductance, as shown in equation below :
⎤
⎡V
⎤ ⎡ V
ΔIL = ⎢ OUT ⎥ × ⎢1− OUT ⎥
VIN ⎦
⎣ f ×L ⎦ ⎣
where f is the operating frequency and L is the inductance.
Having a lower ripple current reduces not only the ESR
losses in the output capacitors, but also the output voltage
ripple. Higher operating frequency combined with smaller
ripple current is necessary to achieve high efficiency. This,
however, requires a large inductor.
A reasonable starting point for selecting the ripple current
is ΔIL = 0.4I(MAX). The largest ripple current occurs at the
highest VIN. To guarantee that the ripple current stays
below a specified maximum, the inductor value should be
chosen according to the following equation :
⎡ VOUT ⎤ ⎡
VOUT ⎤
L=⎢
⎥ × ⎢1−
⎥
⎢⎣ f × ΔIL(MAX) ⎥⎦ ⎢⎣ VIN(MAX) ⎥⎦
CIN and COUT Selection
The input capacitance, C IN, is needed to filter the
trapezoidal current at the source of the high side MOSFET.
To prevent large ripple voltage, a low ESR input capacitor
sized for the maximum RMS current should be used. RMS
current is given by :
V
VIN
IRMS = IOUT(MAX) × OUT ×
−1
VIN
VOUT
This formula has a maximum at VIN = 2VOUT, where
IRMS = IOUT(MAX) / 2. Several capacitors may also be
paralleled to meet size or height requirements in the design.
The selection of COUT is determined by the effective series
resistance (ESR) that is required to minimize voltage ripple
and load step transients, as well as the amount of bulk
capacitance that is necessary to ensure that the control
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8
The output ripple, ΔVOUT, is determined by :
⎡
⎤
1
ΔVOUT ≤ ΔIL × ⎢ESR +
⎥
8fC
OUT ⎦
⎣
Using Ceramic Input and Output Capacitors
Higher values, lower cost ceramic capacitors are now
becoming available in smaller case sizes. Their high ripple
current, high voltage rating and low ESR make them ideal
for switching regulator applications. However, care must
be taken when these capacitors are used at the input and
output. When a ceramic capacitor is used at the input
and the power is supplied by a wall adapter through long
wires, a load step at the output can induce ringing at the
input, VIN. At best, this ringing can couple to the output
and be mistakened as loop instability. At worst, a sudden
inrush of current through the long wires can potentially
cause a voltage spike at VIN large enough to damage the
part.
Output Voltage Programming
The resistive divider allows the FB pin to sense a fraction
of the output voltage as shown below
DS9996-01 April 2011
RT9996
Voltage Detector
RT9996
LX
VOUT
R1
FB
R2
RESET is an open drain output that indicates whether
the VDET voltage is higher than 0.7V or not. RESET is
typically pulled up to 3.3V. VDET monitors the input
voltage and triggers the RESET output (Figure 1).
GND
For adjustable voltage mode, the output voltage is set by
an external resistive divider according to the following
equation :
VOUT = VFB × ⎛⎜ 1+ R1 ⎞⎟
⎝ R2 ⎠
RESET is high impedance when the voltage from VDET
exceeds the rising threshold 0.7V (typ.). RESET is low
when the voltage from VDET falls below the low-battery
falling threshold 0.68V (typ.) (Figure 2).
If the voltage detector feature is not required, connect
RESET to ground and connect VDET to VIN.
3.3V
where VFB is the internal reference voltage 0.8V (typ.).
Checking Transient Response
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, VOUT immediately shifts by an amount
equal to ΔILOAD (ESR), where ESR is the effective series
resistance of COUT. ΔILOAD also begins to charge or
discharge COUT generating a feedback error signal used
by the regulator to return VOUT to its steady-state value.
RESET
Table 1. The RT9996 Power Terminology
Buck 1
ON
VIN > EN1 > 1.5V
5.5V > VIN > 2.1V
DS9996-01 April 2011
VDET
0.7V
RESET
Delay
If the EN pin for the selected buck is pulled high and the
input voltage is greater than the under voltage lockout
threshold, the selected buck will be turned on. Buck1
can be turned on/off by the external EN1 pin; Buck2 can
be turned on/off by the external EN2 pin; Buck3 can be
turned on/off by the external EN3 pin.
Default
Output
Voltage
-
VDET
Chip Enable Operation
Output
State
EN
UVLO
0.7V
Figure 1. VDET and RESET Circuit
0.68V
During this recovery time, VOUT can be monitored for
overshoot or ringing which would indicate a stability
problem.
+
Buck 2
ON
VIN > EN2 > 1.5V
5.5V > VIN > 2.1V
R1 ⎞
VOUT = VFB × ⎛⎜ 1 +
⎟
⎝ R2 ⎠
VFB = 0.8V
Figure 2. VDET and RESET Comparator Waveform
Choosing the Inductor
The RT9996 includes a current-reversal comparator which
monitors inductor current and disables the synchronous
rectifier as current approaches zero. This comparator will
minimize the effect of current reversal for higher efficiency.
For some low inductance values, however, the inductor
current may still reverse slightly. This value depends on
the speed of the comparator in relation to the slope of the
current waveform, given by VL / L. VL is the voltage across
the inductor (approximately −VOUT) and L is the inductance
value.
An inductance value of 2.2μH is a good starting value. As
the inductance is reduced from this value, the RT9996
will enter discontinuous conduction mode at progressively
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9
RT9996
higher loads. Ripple at VOUT will increase directly proportionally to the magnitude of inductor ripple. Transient response,
however, will improve.
A smaller inductor changes its current more quickly for a given voltage drive than a larger inductor, resulting in faster
transient response. A larger inductor will reduce output ripple and current ripple, but at the expense of reduced transient
performance and a physically larger inductor package size. For this reason a larger CVOUT will be required for larger
inductor sizes.
The input regulator has an instantaneous peak current clamp to prevent the inductor from saturating during transient load
or start-up conditions. The clamp is designed so that it does not interfere with normal operation at high loads and
reasonable inductor ripple. It is intended to prevent inductor current runaway in case of a shorted output.
The DC winding resistance and AC core losses of the inductor will also affect efficiency, and therefore available output
power. These effects are difficult to characterize and vary by application. Some inductors and capacitors that may be
suitable for this application are listed in Table below :
Table 2
Length
(mm)
Max.
VLF5012ST-1R0N2R5
5
VLF5014ST-2R2M2R3
5
VLF3010A-1
3
VLF3012A
3
VLS2010E
2.1
VLS2012E
2.1
NR6045T1R0N
6
CB2016T2R2M
2.2
NR6020T2R2N
6
NR3015
3
LPS4018
3.9
D53LC
5
DB318C
3.8
WE-TPC Type M1
4.8
p/n
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10
Width
(mm)
Max.
4.8
4.8
2.8
2.8
2.1
2.1
6
1.8
6
3
3.9
5
3.8
4.8
Height Inductance
(mm)
(μH)
Max.
L
1.2
1
1.4
2.2
1
2.2
1.2
2.2
1
2.2
1.2
2.2
4.5
1
1.8
2.2
2
2.2
1.5
2.2
1.7
3.3
3
3.3
1.8
3.3
1.8
3.3
RDC
(mΩ)
Max.
50
73
120
100
228
153
19
130
34
60
80
34
70
65
IDC
(A)
Supplier
Max.
3.3
3
1
TDK
1
1
1
4.2
1
TAIYO
2.7
1.48
2.2
CoilCraft
2.26
Toko
1.55
1.95
Wurth
DS9996-01 April 2011
RT9996
Thermal Considerations
Layout Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
Follow the PCB layout guidelines for optimal performance
of RT9996.
PD(MAX) = (TJ(MAX) − TA) / θJA
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
For recommended operating condition specifications of
the RT9996, the maximum junction temperature is 125°C
and TA is the ambient temperature. The junction to ambient
thermal resistance, θJA, is layout dependent. For VQFN-
`
Place the input capacitor as close as possible to the
device pins (VIN and GND).
`
LX node is with high frequency voltage swing and should
be kept in a small area.
`
Connect feedback network behind the output capacitors.
`
Keep the switching area small. Place the feedback
components near the RT9996.
`
Connect all analog grounds to a common node and then
connect the common node to the power ground behind
the output capacitors.
32L 5x5 packages, the thermal resistance, θJA , is 36°C/
W on a standard JEDEC 51-7 four-layer thermal test board.
The maximum power dissipation at TA = 25°C can be
calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (36°C/W) = 2.778W for
VQFN-32L 5x5 package
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA . For the RT9996 package, the derating
curve in Figure 3 allows the designer to see the effect of
rising ambient temperature on the maximum power
dissipation.
Maximum Power Dissipation (W)1
3.0
Four-Layer PCB
2.7
2.4
2.1
1.8
1.5
1.2
0.9
0.6
0.3
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 3. Derating Curve for the RT9996 Package
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11
RT9996
Outline Dimension
D2
D
SEE DETAIL A
L
1
E
E2
e
b
1
2
2
DETAIL A
Pin #1 ID and Tie Bar Mark Options
A
A1
1
A3
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.800
1.000
0.031
0.039
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.180
0.300
0.007
0.012
D
4.950
5.050
0.195
0.199
D2
3.400
3.750
0.134
0.148
E
4.950
5.050
0.195
0.199
E2
3.400
3.750
0.134
0.148
e
L
0.500
0.350
0.020
0.450
0.014
0.018
V-Type 32L QFN 5x5 Package
Richtek Technology Corporation
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: [email protected]
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit
design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be
guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
www.richtek.com
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DS9996-01 April 2011