EP1551

Preliminary
EP1551
1 MHz Five-channel Power Supply
FEATURES
APPLICATIONS
‧ Up to 95% efficiency Step-up and up to 92%
‧ Digital still camera
efficient Step-down converters
‧ Digital video camera
‧ Combine Step-up and Step-down for up to 87%
efficiency buck-boost operations
‧ PDA
‧ MP3
‧ Minimum 0.7V input voltage
‧ PMP
‧ 2µA shutdown mode
‧ Portable DVD Player
‧ Internal soft start control
‧ Car navigation
‧ Overload protection
‧ Compact QFN-32 5 x 5 mm package
DESCRIPTION
The EP1551 is a small, high efficiency, five-channel, power-supply for digital still and video cameras.
It consists
of:
‧ Step-up DC-DC converter with on-chip power MOSFETs for 3.3V main system supply with up to 95%
efficiency. It accepts inputs from 0.7V to 5.5V and regulates a resistor-adjustable output from 2.7V to 5.5V.
‧ Step-down main DC-DC converter with on-chip power MOSFETs for 1.5V DSP core supply with up to 92%
efficiency. It can operate from the Step-up main system supply providing buck-boost capability with up to 90%
compound efficiency, or it can run directly from battery if buck-boost operation is not needed.
‧ PWM controller with external FET for Step-up DC-DC converter for 5V motor actuator
‧ PWM controller with external FET for 15V LCD supply
‧ PWM controller with external FET and transformer for –7.5V and +15V CCD Bias
All DC-DC channels operate at one fixed frequency settable from 100KHz to 1MHz to optimize size, cost and
efficiency. Other features include soft-start, power-OK outputs, and overload protection. The EP1551 is available
in apace saving QFN-32 5 x 5 mm packages. An evaluation kit is also available to expedite design.
Rev.01
1/16
EP1551
Preliminary
EP 1551
Figure 1. Basic Application Circuit with EP1551 example
Package/ Order Information
Eorex
Power Management
Multi-channel
Power-supply
Series Number
E
P
15
51
Rev.01
2/16
EP1551
Preliminary
Absolute Maximum Rating (Note 1)
OUTBU_, INSD, SDOK, ON_, FB_, FBSEL_ to GND................................ -0.3V to +6V
PGND to GND ........................................................................................ -0.3V to +0.3V
DL_to PGND...............................................................................-0.3V to OUTSU+0.3V
LXSU Current
(Note 2)
................................................................................................3.6A
LXSD Current
(Note 2)
..............................................................................................2.25A
REF, OSC, COMP_ to GND........................................................-0.3V to OUTSU+0.3V
Continuous Power Dissipation (TA=70°C, derate 22mW/°C above +70°C)......1700Mw
Operating Temperature Range.............................................................. -40°C to +85°C
Junction Temperature ........................................................................................+150°C
Storage Temperature Range............................................................... -65°C to +150°C
Lead Temperature (Soldering, 10s) ...................................................................+150°C
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Note 2: LXSU has internal clamp diodes to OUTSU and PGND, and LXSD has internal clamp diodes to
INSD and PGND. Applications that forward bias these diodes should take care not to exceed the
devices power dissipation limits.
Electrical Characteristics
(VOUTSU = 3.3V, TA = 0°C to +85°C, unless otherwise noted.)
Parameter
Conditions
MIN
TYP
MAX
unit
5.5
V
1.2
1.4
V
GENERAL:
Input Voltage Range
Minimum Startup Voltage
0.7
ILOAD < 1mA, TA = +25°C
Thermal Shutdown
160
Thermal-Shutdown Hysteresis
°C
20
°C
Shutdown Supply Current into
OUTSU
ONSU = ONSD = ON1 = ON2 = ON3
= 0, OUTSU = 3.6V
0.3
5
µA
Step-up DC-DC Supply Current
into OUTSU
ONSU = 3.35v, FBSU = 1.5V (does
not include switching losses)
320
400
µA
Step-up Plus 1 AUX Supply
Current into OUTSU
ONSU = ON_ = 3.35V,
FBSU = 1.5V, FB_= 1.5V
(does not include switching losses)
385
600
µA
Step-up Plus Step-down
Supply Current into OUTSU
ONSU = ONSD = 3.35V, FBSU =
1.5V, FBSD = 1.5V (does not include
switching losses)
1030
1300
µA
Reference Output Voltage
IREF = 20 µA
1.25
1.275
V
Reference Load Regulation
10µA < IREF < 200µA
4.5
10
mV
Reference Line Regulation
2.7 < OUTSU < 5.5V
1.3
5
mV
OSC Discharge Trip Level
Rising edge
1.25
1.275
V
OSC Discharge Resistance
OSC = 1.5v, IOSC = 3mA
52
80
OSC Discharge Pulse Width
OSC Frequency
ROSC = 40K., COSC = 100pF
Rev.01
1.225
1.225
Ω
230
ns
400
KHz
3/16
EP1551
Preliminary
Parameter
Conditions
MIN
TYP
MAX
unit
2.3
2.5
2.6
V
STEP-UP DC-DC CONVERTER :
Step-up
Startup-to-Normal
Operating Threshold
Rising or falling edge
80
Step-up Startup-to-Normal
Operating Threshold
Hysteresis
2.7
Step-up Voltage Adjust Range
FBSU Regulation Voltage
mV
5.5
V
V
1.225
1.25
1.275
OUTSU Regulation Voltage
FBSELSU = GND
3.250
3.350
3.450
V
FBSU to COMPSU
Transconductance
FBSU = COMPSU
80
135
185
µS
FBSU Input Leakage Current
FBSU =1.25V
-100
1
100
nA
150
200
265
Idle-Mode Trip Level
Current-Sense Amplifier
Transresistance
Step-up Maximum Duty Cycle
0.3
FBSU = 1V
80
85
mA
V/A
90
%
OUTSU Leakage Current
VLXSU = 0V, OUTSU = 5.5V
0.01
20
µA
LXSU Leakage Current
VLXSU = OUTSU = 5.5V
0.01
20
µA
Switch On-Resistance
N-channel
95
105
P-channel
150
250
mΩ
N-Channel Current Limit
2
A
P-Channel Turn-Off Current
20
mA
Startup Current Limit
OUTSU = 1.8V
Startup tOFF
OUTSU = 1.8V
Startup Frequency
OUTSU = 1.8V
1.2
0.3
670
mA
515
ns
244
KHz
STEP-DOWN DC-DC CONVERTER :
FBSD Regulation Voltage
1.225
1.25
1.275
V
OUTSD Regulation Voltage
FBSELSD=GND
1.470
1.500
1.530
V
FBSD TO COMPSD
Transconductance
FBSD=COMPSD
80
135
185
uS
FBSD Input Leakage Current
FBSD=1.25V
-100
1
100
nA
110
160
190
mA
Idle-Mode Trip level
Current-Sense Amplifier
Transresistance
LXSD Leakage Current
Switch On-Resistance
0.6
VLXSD = 5.5V OUTSU = 5.5V
0.01
20
VLXSD = 0V OUTSU = 5.5V
0.01
20
N-channel
90
150
P-channel
150
250
P-channel Current Limit
N-channel Turn-off Current
Soft-start Interval
SDOK Output Low Voltage
V/A
FBSD=0.4v, 0.1mA into SDOK pin
SDOK Operating Voltage
Rev.01
Ω
0.79
A
20
mA
4096
OSC
cycle
0.002
1
µA
0.1
V
5.5
V
4/16
EP1551
Preliminary
Parameter
Conditions
MIN
TYP
MAX
unit
80
85
90
%
1.225
1.25
1.275
V
185
µS
AUXILIARY DC-DC CONTROLLERS (AUX 1, 2, AND 3) :
Maximum Duty Cycle
FB_ = 1V
FB_ Regulation Voltage
FB_ to COMP_
Transconductance
FB_ = COMP_
80
135
FB_ Input Leakage Current
FBSU =1.25V
-100
2
100
nA
AUX1 Output Regulation
Voltage
FBSEL1 = GND, FB1connected
directly AUX1 output
4.85
5
5.15
V
DL_ Driver Resistance
Output high
3
10
Ω
2
5
Output low
DL_ Driver Current
Sourcing or sinking
Soft-Start Interval
0.5
A
4096
OSC
cycle
LOGIC INPUTS (ON_, FBSEL):
Input Low Level
Input High Level
1.1V < OUTSU < 1.8V (ONSU only)
0.2
1.8V < OUTSU < 5.5V
0.4
1.1V < OUTSU < 1.8V (ONSU only)
1.8V < OUTSU < 5.5V
VOUT
SU
-0.2
V
V
1.6
FBSEL_ Input Leakage
Current
FBSEL = 3.6V, OUTSU = 3.6V
-100
0
100
FBSEL = GND, OUTSU = 3.6V
-100
0
100
ONSU Impedance to GND
ONSU=3.35V
303
KΩ
ONSD Impedance to GND
ONSD=3.35V
275
KΩ
ON_ Impedance to GND
ON_ =3.35V
308
KΩ
Rev.01
5/16
nA
EP1551
Preliminary
Typical Operating Characteristics
(Circuit of Figure 2, TA = 25°C, unless otherwise noted.)
Figure 2, Typical Application Circuit (EP1551 Evaluation Board schematic)
STEP-UPEFFICIENCY vs. LOAD CURRENT
(3.3V OUTPUT)
100%
90%
80%
70%
60%
50%
40%
Efficiency
@Vin=3.6V
Efficiency
@Vin=3.3V
Efficiency
@Vin=2.5V
30%
20%
10%
0%
1
10
100
1000
Figure 3. EP1551 Step-up Efficiency vs Load Current
Rev.01
6/16
EP1551
Preliminary
STEP-DOWN EFFICENCY vs. LOAD CURRENT
(1.5V Output Voutsu=3.3V)
100%
90%
80%
70%
60%
50%
Efficiency
@Vin=3V
Efficiency
@Vin=3.6V
Efficiency
@Vin=4.2V
40%
30%
20%
10%
0%
1
10
100
1000
Figure 4. EP1551 Step-down Efficiency vs. Load Current
BUCK-BOOSTEFFICIENCY vs. LOAD CURRENT
(1.5V OUTPUT, Voutsu=3.3V)
90%
80%
70%
60%
50%
40%
Efficiency
@Vin=1.5V
Efficiency
@Vin=2V
Efficiency
@Vin=3V
30%
20%
10%
0%
1
10
100
1000
Figure 5. EP1551 Buck-Boost Efficiency vs. Load Current
Rev.01
7/16
Preliminary
EP1551
Figure 6. EP1551 Auxiliary PWM Step-up Efficiency vs. Load Current
Rev.01
8/16
Preliminary
EP1551
Functional Block Diagram
Figure 7. Block Diagram for EP1551
Pin Description
PIN
NAME
FUNCTION
Auxiliary Controller 1 Compensation Node. Connect a series RC from COMP1 to GND to
1
COMP1
compensate the control loop. COMP1 is actively driven to GND in shutdown and thermal
limit.
Auxiliary Controller 1 Feedback Input. For 5V output, short FBSEL1 to GND and
connect FB1 to the output voltage. For other output voltages, connect FBSEL1 to
2
FB1
OUTSU and connect a resistive voltage-divider from the Step-up converter output to
FB1 to GND. The FB1 feedback threshold is then 1.25V. This pin is high impedance in
shutdown.
3
PGNDA
Power Ground. Connect PGNDA and PGNDB together and to GND with short trace as
close to the IC as possible.
Step-down Converter Power-Switching Node. Connect LXSD to the Step-down
4
LXSD
converter inductor. LXSD is the drain of the P-channel switch and N-channel
synchronous rectifier. LXSD is high impedance in shutdown.
5
INSD
Step-down Converter Input. INSD can connect to OUTSU, effectively making OUTSD a
buck-boost output from the battery. Bypass to GND with a 1µF ceramic capacitor if
Rev.01
9/16
Preliminary
EP1551
connected to OUTSU. INSD may also be connected to the battery, but should not
exceed OUTSU by more than a Schottky diode forward voltage. Bypass INSD with a
10µF ceramic capacitor when connecting to the battery input. A 10kΩ internal resistance
connects OUTSU and INSD.
Step-down Converter On/Off Control Input. Drive ONSD high to turn on the Step-down
6
ONSD
converter. This pin has an internal 330k. pull down resistor. ONSD does not start until
OUTSU is in regulation.
Step-down Converter Compensation Node. Connect a series RC from COMPSD to GND
7
COMPSD
to compensate the control loop. COMPSD is pulled to GND in normal shutdown and
during thermal shutdown.
Step-down Converter Feedback Input. For a 1.5V output, short FBSELSD to GND and
8
FBSD
connect FBSD to OUTSD. For other voltages, short FBSELSD to OUTSU and connect a
resistive voltage-divider from OUTSD to FBSD to GND. The FBSD feedback threshold is
1.25V. This pin is high impedance in shutdown.
9
ON1
10
ON2
11
ON3
Auxiliary Controller 1 On/Off Control Input. Drive ON1 high to turn on. This pin has an
internal 330k. pull down resistor. ON1 cannot start until OUTSU is in regulation.
Auxiliary Controller 2 On/Off Control Input. Drive ON2 high to turn on. This pin has an
internal 330k. pull down resistor. ON2 cannot start until OUTSU is in regulation.
Auxiliary Controller 3 On/Off Control Input. Drive ON3 high to turn on. This pin has an internal
330kΩ pull down resistor. ON3 cannot start until OUTSU is in regulation.
Step-up Converter On/Off Control. Drive ONSU high to turn on the Step-up converter.
12
ONSU
All other control pins are locked out until 2ms after the Step-up output has reached its
final value. This pin has an internal 330k. resistance to GND.
Reference Output. Bypass REF to GND with a 0.1µF or greater capacitor. The
13
REF
maximum allowed load on REF is 200µA. REF is actively pulled to GND when all
converters are shut down.
Step-up Converter Feedback Input. To regulate OUTSU to 3.35V, connect FBSELSU to
14
FBSU
GND. FBSU may be connected to OUTSU or GND. For other output voltages, connect
FBSELSU to OUTSU and connect a resistive voltage-divider from OUTSU to FBSU to
GND. The FBSU feedback threshold is 1.25V. This pin is high impedance in shutdown.
Step-up Converter Compensation Node. Connect a series RC from COMPSU to GND to
15
COMPSU
compensate the control loop. COMPSD is pulled to GND in normal shutdown and during
thermal shutdown.
Step-up Feedback Select Pin. With FBSELSU = GND, OUTSU regulates to 3.35V. With
16
FBSELSU
FBSELSU = OUTSU, FBSU regulates to a 1.25V threshold for use with external
feedback resistors. This pin is high impedance in shutdown.
Step-down Feedback Select Pin. With FBSELSD = GND, FBSD regulates to 1.5V. With
17
FBSELSD
FBSELSD = OUTSU, FBSD regulates to 1.25V for use with external feedback resistors.
This pin is high impedance in shutdown.
Auxiliary Controller 1 Feedback Select Pin. With FBSEL1 = GND and FB1 regulates to
18
FBSEL1
5V. With FBSEL1 = OUTSU, FB1 regulates to 1.25V for use with external feedback
resistors. This pin is high impedance in shutdown.
19
OSC
Oscillator Control. Connect a timing capacitor from OSC to GND and a timing resistor
from OSC to OUTSU to set the oscillator frequency between 100kHz and 1MHz. This
Rev.01
10/16
Preliminary
EP1551
pin is high impedance in shutdown.
20
PGNDB
21
LXSU
22
OUTSUA
23
SDOK
Power Ground. Connect PGNDA and PGNDB together and to GND with short trace as
close to the IC as possible.
Step-up Converter Power-Switching Node. Connect LXSU to the Step-up converter
inductor. LXSU is high impedance in shutdown.
Step-up Converter Output. OUTSUA is the power output of the Step-up converter.
Connect OUTSUA to OUTSUB at the IC.
This open-drain output goes high impedance when the Step-down has successfully
completed soft-start.
Auxiliary Controller 3 Compensation Node. Connect a series resistor-capacitor from
24
COMP3
COMP3 to GND to compensate the control loop. COMP3 is actively driven to GND in
shutdown and thermal limit.
Auxiliary Controller 3 Feedback Input. Connect a resistive voltage-divider from the
25
FB3
output voltage to FB3 to GND. The FB3 feedback threshold is 1.25V. This pin is high
impedance in shutdown.
26
OUTSUB
27
DL3
Step-up Converter Output. OUTSUB powers the EP1551 and is the sense input when
FBSELSU is GND and the output is 3.3V. Connect OUTSUA to OUTSUB.
Auxiliary Controller 3 Gate-Drive Output. Connect the gate of an N-channel MOSFET to
DL3. DL3 swings from GND to OUTSU and supplies up to 500mA. DL3 is driven to GND
in shutdown and thermal limit.
Auxiliary Controller 2 Gate-Drive Output. Connect the gate of an N-channel MOSFET to
28
DL2
DL2. DL2 swings from GND to OUTSU and supplies up to 500mA. DL2 is driven to GND
in shutdown and thermal limit.
Auxiliary Controller 1 Gate-Drive Output. Connect the gate of an N-channel MOSFET to
29
DL1
DL1. DL1 swings from GND to OUTSU and supplies up to 500mA. DL1 is driven to GND
in shutdown and thermal limit.
30
GND
Quiet Ground. Connect GND to PGND as close to the IC as possible.
Auxiliary Controller 2 Compensation Node. Connect a series resistor-capacitor from
31
COMP2
COMP2 to GND to compensate the control loop. COMP2 is actively driven to GND in
shutdown and thermal limit.
Auxiliary Controller 2 Feedback Input. Connect a resistive voltage-divider from the
32
FB2
output voltage to FB2 to GND to set the output voltage. The FB2 feedback threshold is
1.25V. This pin is high impedance in shutdown.
Exposed
Pad
Exposed Underside Metal Pad. This pad must be soldered to the PC board to achieve
EP
package thermal and mechanical ratings. The exposed pad is electrically connected to
GND.
Rev.01
11/16
Preliminary
EP1551
OPERATION
‧ EP1551 includes five channels, a current-mode Step-up DC-DC converter, a current-mode Step-down DC-DC
converter, and three auxiliary voltage-mode DC-DC controllers. All these channels employ fixed frequency
PWM operator.
‧ Step-up is typically used to supply 3.3V for main system power. Reference voltage and clocks are also
generated in this channel.
‧
SUSSD (Step-up timer done) keeps low for 1,024 clock cycles after ONSU goes high, which means in
typical application case (clock frequency equals 400kHz), the other four channels will be enabled after
2.56ms.
‧
Step-down DC-DC converter can be powered from the battery, or from the output of Step-up DC-DC
converter.
‧
Three auxiliary controllers are almost same, but only AUX1 has optional internal divider for feedback.
‧
If any channel remains faulted (no reset signal generated by the comparator) for 100,000 clock cycles, then
_FLTALL goes low, all outputs latch off until the Step-up DC-DC converter is reinitialized by ONSU, or by
cycling of input power. The fault-detection for any channel is disabled during its initial turn-on soft-start
sequence.
Step-up DC-DC Converter
Figure 8. Block Diagram for Current-Mode Step-up DC-DC Converter
Rev.01
12/16
Preliminary
‧
EP1551
During startup, P-channel switch transistor is always off, N-channel switch transistor is controlled by
startup oscillator’s output. N-channel switch transistor has fixed off time, its on time is determined by
startup current limit, inductor value, and input voltage.
‧
When OUTSU reaches 2.5V, startup is complete, and the main circuits begin to work.
‧
The oscillator’s frequency is determined by the RC network at OSC pin and the output voltage of Step-up
DCDC converter, so the frequency changes as OUTSU ramps upward following startup.
‧
Current sense amplifier (Isense AMP) senses inductor current when N-channel switch transistor is on.
When inductor’s peak current reaches 2A, N-channel switch transistor will be turned off.
‧
Reverse current sense amplifier (Izero AMP) senses inductor current when P-channel switch transistor is
on. When inductor current falls to zero, P-channel switch transistor will be turned off.
‧
If Step-up DC-DC converter has moderate or heavy load, inductor current is controlled by the output of
error amplifier (ERR AMP). With light load, Step-up DC-DC converter operates in idle-mode to improve
the efficiency. In idle-mode, peak current of every pulse is fixed at 200mA, and some pulses are skipped.
Step-down DC-DC Converter
Figure 9. Block Diagram for Current-Mode Step-down DC-DC Converter
‧ The structure of Step-down DC-DC converter is similar to that of Step-up DC-DC converter. Soft-start circuit is
used to ramp the internal reference up from 0V to 1.25V.
Rev.01
13/16
Preliminary
EP1551
Auxiliary DC-DC Controllers
Figure 10. Block Diagram for Voltage-Mode Auxiliary DC-DC Controllers
‧ The three auxiliary voltage-mode DC-DC controllers are almost same. The only difference is just AUX1 has
optional internal divider. AUX2 and AUX3 must use external divider for feedback. Soft-start circuit is used
to ramp internal reference up from 0V to 1.25V. Output pulse width is modulated by the output of error
amplifier (ERR AMP).
Rev.01
14/16
Preliminary
EP1551
Package Description
QFN-32
5 x 5 mm
DIMENSIONS：
A
A1
0.70
0.00
NOM. 0.75
0.02
MAX. 0.80
0.05
MIN.
A3
0.2 ref.
b
D
E
0.20
4.90
4.90
0.25
5.00
5.00
0.30
5.10
5.10
e
0.5 bsc.
k
L
0.25
0.30
-
0.40
-
0.50
N
32
ND NE
8
8
SIDE VIEW：
TERMINAL：
Rev.01
15/16
Preliminary
EP1551
Top View:
Bottom View:
Rev.01
16/16