MAXIM MAX1565

19-2712; Rev 0; 1/03
KIT
ATION
EVALU
E
L
B
A
AVAIL
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
Features
♦ Step-Up DC-to-DC Converter
95% Efficient
3.3V (Fixed) or 2.7V to 5.5V (Adjustable) Output
Voltage
♦ Step-Down DC-to-DC Converter
Operate from Battery for 95% Efficient Buck
Combine with Step-Up for 90% Efficient BuckBoost
Adjustable Output Down to 1.25V
♦ Three Auxiliary PWM Controllers
♦ Up to 1MHz Operating Frequency
♦ 1µA Shutdown Mode
♦ Internal Soft-Start Control
♦ Overload Protection
♦ Compact 32-Pin, 5mm x 5mm Thin QFN Package
Ordering Information
PART
MAX1565ETJ
TEMP RANGE
PIN-PACKAGE
-40°C to +85°C
32 Thin QFN
The MAX1565 is available in a space-saving 32-pin thin
QFN package.
Pin Configuration
CORE +1.5V
AUX1
MOTOR +5V
AUX2
CCD +15V/-7.5V
AUX3
LCD, LED +15V
GND
DL1
DL2
DL3
OUTSUB
FB3
26
25
24 COMP3
FB1
2
23 SDOK
PGNDA
3
22 OUTSUA
LXSD
4
INSD
5
ONSD
6
19 OSC
COMPSD
7
18 FBSEL1
FBSD
8
17 FBSELSD
21 LXSU
MAX1565
9
10
20 PGNDB
11
12
13
14
15
16
FBSELSU
STEP-DOWN
27
COMPSU
ON2
0N3
MAIN +3.3V
28
FBSU
ON/OFF
CONTROLS
ONSU
ONSD
ON1
STEP-UP
29
REF
MAX1565
30
ONSU
INPUT
+0.7V TO +5.5V
31
1
ON3
Typical Operating Circuit
32
COMP1
ON2
PDAs
COMP2
Digital Video Cameras
FB2
TOP VIEW
Digital Still Cameras
ON1
Applications
5mm x 5mm
THIN QFN
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX1565
General Description
The MAX1565 provides a complete power-supply solution
for digital still and video cameras through the integration
of ultra-high-efficiency step-up/step-down DC-to-DC converters along with three auxiliary step-up controllers. The
MAX1565 is targeted for applications that use either 2 or
3 alkaline or NiMH batteries as well as those using a
single lithium-ion (Li+) battery.
The step-up DC-to-DC converter accepts inputs from
0.7V to 5.5V and regulates a resistor-adjustable output
from 2.7V to 5.5V. It uses internal MOSFETs to achieve
95% efficiency. Adjustable operating frequency facilitates design for optimum size, cost, and efficiency.
The step-down DC-to-DC converter can produce output
voltages as low as 1.25V and also utilizes internal
MOSFETs to achieve 95% efficiency. An internal softstart ramp minimizes surge current from the battery.
The converter can operate from the step-up output providing buck-boost capability with up to 90% compound
efficiency, or it can run directly from the battery if buckboost operation is not needed.
The MAX1565 features auxiliary step-up controllers that
power CCD, LCD, motor actuator, and backlight circuits. The device also features low-cost expandability
by supplying power, an oscillator signal, and a reference to the MAX1801 SOT23 slave controller that supports step-up, SEPIC, and flyback configurations.
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
ABSOLUTE MAXIMUM RATINGS
OUTSU_, 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 1) ..........................................................3.6A
LXSD Current (Note 1) ........................................................2.25A
REF, OSC, COMP_ to GND.....................-0.3V to OUTSU + 0.3V
Continuous Power Dissipation (TA =+70°C)
32-Pin Thin QFN (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) .................................+300°C
Note 1: 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.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and 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 affect device reliability.
ELECTRICAL CHARACTERISTICS
(VOUTSU = 3.3V, TA = 0°C to +85°C, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
1.1
V
GENERAL
Input Voltage Range
(Note 2)
Minimum Startup Voltage
ILOAD < 1mA, TA = +25°C, startup voltage tempco is
-2300ppm/°C (typ) (Note 3)
0.7
0.9
100,000
OSC
cycles
Thermal Shutdown
160
°C
Thermal-Shutdown Hysteresis
20
°C
Overload Protection Fault Interval
Shutdown Supply Current into
OUTSU
ONSU = ONSD = ON1 = ON2 = ON3 = 0; OUTSU = 3.6V
0.1
5
µA
Step-Up DC-to-DC Supply
Current into OUTSU
ONSU = 3.35V, FBSU = 1.5V
(does not include switching losses)
290
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)
420
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)
470
650
µA
Reference Output Voltage
IREF = 20µA
1.25
1.27
V
Reference Load Regulation
10µA < IREF < 200µA
4.5
10
mV
Reference Line Regulation
2.7 < OUTSU < 5.5V
mV
OSC Discharge Trip Level
Rising edge
OSC Discharge Resistance
OSC = 1.5V, IOSC = 3mA
1.23
1.225
OSC Discharge Pulse Width
OSC Frequency
ROSC = 40kΩ, COSC = 100pF
1.3
5
1.25
1.275
V
52
80
Ω
300
ns
400
kHz
STEP-UP DC-TO-DC CONVERTER
Step-Up Startup-to-Normal
Operating Threshold
Step-Up Startup-to-Normal
Operating Threshold Hysteresis
2
Rising or falling edge (Note 4)
2.30
2.5
80
_______________________________________________________________________________________
2.60
V
mV
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
(VOUTSU = 3.3V, TA = 0°C to +85°C, unless otherwise noted.)
PARAMETER
CONDITIONS
Step-Up Voltage Adjust Range
MIN
TYP
MAX
UNITS
5.5
V
1.231
1.25
1.269
V
2.7
FBSU Regulation Voltage
OUTSU Regulation Voltage
FBSELSU = GND
3.296
3.35
3.404
V
FBSU to COMPSU
Transconductance
FBSU = COMPSU
80
135
185
µS
FBSU Input Leakage Current
FBSU = 1.25V
-100
+1
+100
nA
Idle-Mode™ Trip Level
(Note 6)
150
200
265
mA
Current-Sense Amplifier
Transresistance
0.3
Step-Up Maximum Duty Cycle
FBSU = 1V
85
90
%
OUTSU Leakage Current
VLX = 0V, OUTSU = 5.5V
0.01
20
µA
LXSU Leakage Current
VLXSU = VOUT = 5.5V
µA
Switch On-Resistance
80
V/A
0.01
20
N-channel
95
150
P-channel
150
250
2
2.4
N-Channel Current limit
1.6
P-Channel Turn-Off Current
mΩ
A
20
mA
mA
Startup Current Limit
OUTSU = 1.8V (Note 5)
800
Startup tOFF
OUTSU = 1.8V
700
ns
Startup Frequency
OUTSU = 1.8V
200
kHz
STEP-DOWN DC-TO-DC CONVERTER
FBSD Regulation Voltage
1.231
1.25
1.269
V
OUTSD Regulation Voltage
FBSELSD = GND
1.48
1.5
1.52
V
FBSD to COMPSD
Transconductance
FBSD = COMPSD
80
135
185
µS
FBSD Input Leakage Current
FBSD = 1.25V
-100
+1
+100
nA
Idle-Mode Trip Level
(Note 6)
110
160
190
mA
Current-Sense Amplifier
Transresistance
LXSD Leakage Current
Switch On-Resistance
0.60
VLXSD = 5.5V, OUTSU = 5.5V
0.01
20
VLXSD = 0V, OUTSU = 5.5V
0.01
20
N-channel
95
150
P-channel
150
250
0.79
1.0
P-Channel Current Limit
0.7
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 Range
mΩ
A
20
mA
4096
OSC
cycles
0.002
1.0
µA
0.1
V
5.5
V
Idle Mode is a trademark of Maxim Integrated Products, Inc.
_______________________________________________________________________________________
3
MAX1565
ELECTRICAL CHARACTERISTICS (continued)
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
ELECTRICAL CHARACTERISTICS (continued)
(VOUTSU = 3.3V, TA = 0°C to +85°C, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
AUXILIARY DC-TO-DC CONTROLLERS (AUX 1, 2, AND 3)
Maximum Duty Cycle
FB_ = 1V
80
85
90
%
FB_ Regulation Voltage
FB_ = COMP_
1.231
1.25
1.269
V
FB_ to COMP_
Transconductance
FB_ = COMP_
80
135
185
µS
FB_ Input Leakage Current
FB_ = 1.25V
-100
+1
+100
nA
AUX1 Output Regulation Voltage
FBSEL1 = GND, FB1 connected directly to AUX1 output
4.93
V
DL_ Driver Resistance
DL_ Drive Current
5
5.07
Output high
3
10
Output low
2
5
Sourcing or sinking
Soft-Start Interval
Ω
0.5
A
4096
OSC
cycles
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
FBSEL_ Input Leakage Current
ON_ Impedance to GND
VOUTSU
- 0.2
V
V
1.6
FBSEL = 3.6V, OUTSU = 3.6V
-100
0
+100
FBSEL = GND, OUTSU = 3.6V
-100
0
+100
ON_ = 3.35V
330
nA
kΩ
ELECTRICAL CHARACTERISTICS
(VOUTSU = 3.3V, TA = -40°C to +85°C, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
1.1
V
5
µA
GENERAL
Input Voltage Range
(Note 2)
Minimum Startup Voltage
ILOAD < 1mA, TA = +25°C, startup voltage tempco is
-2300ppm/°C (typ) (Note 3)
Shutdown Supply Current into
OUTSU
ONSU = ONSD = ON1 = ON2 = ON3 = 0
OUTSU = 3.6V
Step-Up DC-to-DC Supply
Current into OUTSU
ONSU = 3.35V, FBSU = 1.5V
(does not include switching losses)
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)
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)
650
µA
Reference Output Voltage
IREF = 20µA
Reference Load Regulation
10µA < IREF < 200µA
4
0.7
1.23
_______________________________________________________________________________________
1.27
V
10
mV
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
(VOUTSU = 3.3V, TA = -40°C to +85°C, unless otherwise noted.)
PARAMETER
CONDITIONS
Reference Line Regulation
2.7V < OUTSU < 5.5V
OSC Discharge Trip Level
Rising edge
OSC Discharge Resistance
OSC = 1.5V, IOSC = 3mA
MIN
1.225
TYP
MAX
UNITS
5
mV
1.275
V
80
Ω
2.30
2.60
V
2.7
5.5
V
STEP-UP DC-TO-DC CONVERTER
Step-Up Startup-to-Normal
Operating Threshold
Rising or falling edge (Note 4)
Step-Up Voltage Adjust Range
FBSU Regulation Voltage
1.225
1.275
V
OUTSU Regulation Voltage
FBSELSU = GND
3.283
3.417
V
FBSU to COMPSU
Transconductance
FBSU = COMPSU
80
185
µS
FBSU Input Leakage Current
FBSU = 1.25V
-100
+100
nA
Idle-Mode Trip Level
(Note 6)
150
275
mA
Step-Up Maximum Duty Cycle
FBSU =1V
80
90
%
OUTSU Leakage Current
VLX = 0V, OUTSU = 5.5V
20
µA
LXSU Leakage Current
VLXSU = VOUT = 5.5V
20
µA
N-channel
150
P-channel
250
Switch On-Resistance
N-Channel Current limit
mΩ
1.6
2.4
A
STEP-DOWN DC-TO-DC CONVERTER
FBSD Regulation Voltage
1.225
1.275
V
OUTSD Regulation Voltage
FBSELSD = GND
1.47
1.53
V
FBSD to COMPSD
Transconductance
FBSD = COMPSD
80
185
µS
FBSD Input Leakage Current
FBSD = 1.25V
-100
+100
nA
Idle-Mode Trip Level
(Note 6)
110
195
mA
LXSD Leakage Current
Switch On-Resistance
VLXSD = 5.5V, OUTSU = 5.5V
20
VLXSD = 0V, OUTSU = 5.5V
20
N-channel
150
P-channel
250
P-Channel Current Limit
SDOK Output Low Voltage
0.7
mΩ
1.0
A
0.1
V
1
5.5
V
80
90
%
1.225
1.275
V
FBSD = 0.4V; 0.1mA into SDOK pin
SDOK Operating Voltage Range
µA
AUXILIARY DC-TO-DC CONTROLLERS (AUX 1, 2, AND 3)
Maximum Duty Cycle
FB_ = 1V
FB_ Regulation Voltage
FB_ = COMP_
_______________________________________________________________________________________
5
MAX1565
ELECTRICAL CHARACTERISTICS (continued)
ELECTRICAL CHARACTERISTICS (continued)
(VOUTSU = 3.3V, TA = -40°C to +85°C, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
80
185
µS
FB_ to COMP_
Transconductance
FB_ = COMP_
FB_ Input Leakage Current
FB_ = 1.25V
-100
+100
nA
AUX1 Output Regulation Voltage
FBSEL1 = GND, FB1 connected directly to AUX1 output
4.90
5.10
V
DL_ Driver Resistance
Output high
10
Output low
5
Ω
LOGIC INPUTS (ON_, FBSEL_)
Input Low Level
1.1V < OUTSU < 1.8V (ONSU only)
0.2
1.8V < OUTSU < 5.5V
0.4
VOUTSU
-0.2
1.1V < OUTSU < 1.8V (ONSU only)
Input High Level
1.8V < OUTSU < 5.5V
FBSEL_ Input Leakage Current
V
V
1.6
FBSEL = 3.6V, OUTSU = 3.6V
-100
+100
FBSEL = GND, OUTSU = 3.6V
-100
+100
nA
The IC is powered from the OUTSU output.
Since the part is powered from OUTSU, a Schottky rectifier, connected from the input battery to OUTSU, is required for
low-voltage startup.
The step-up regulator operates in startup mode until this voltage is reached. Do not apply full load current during startup.
The step-up current limit in startup refers to the LXSU switch current limit, not an output current limit.
The idle-mode current threshold is the transition point between fixed-frequency PWM operation and idle-mode operation
(where switching rate varies with load). The spec is given in terms of inductor current. In terms of output current, the idlemode transition varies with input/output voltage ratio and inductor value. For the step-up, the transition output current is
approximately 1/3 the inductor current when stepping from 2V to 3.3V. For the step-down, the transition current in terms of
output current is approximately 3/4 the inductor current when stepping down from 3.3V to 1.8V.
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Typical Operating Characteristics
(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
STEP-UP EFFICIENCY
vs. LOAD CURRENT
(3.3V OUTPUT)
60
50
VIN = 4V
VIN = 3.6V
VIN = 3V
VIN = 2V
VIN = 1.5V
40
30
20
70
60
50
VIN = 3.6V
VIN = 3V
VIN = 2V
VIN = 1.5V
40
30
VOUT = 5V
0
10
100
LOAD CURRENT (mA)
1000
90
VIN = 4.2V
VIN = 3.6V
VIN = 3V
80
70
60
50
40
30
20
10
1
80
EFFICIENCY (%)
70
90
EFFICIENCY (%)
80
100
MAX1565 toc02
90
6
100
MAX1565 toc01
100
STEP-DOWN EFFICIENCY
vs. LOAD CURRENT
INSD CONNECTED TO BATTERY
VOUT = 1.5V
DOES NOT INCLUDE CURRENT USED
BY THE STEP-UP TO POWER THE IC
20
10
VOUT = 3.3V
0
1
MAX1565 toc03
STEP-UP EFFICIENCY
vs. LOAD CURRENT
(5V OUTPUT)
EFFICIENCY (%)
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
10
100
LOAD CURRENT (mA)
1000
10
0
1
10
100
LOAD CURRENT (mA)
_______________________________________________________________________________________
1000
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
70
50
40
60
50
30
30
20
20
VOUTSD = 1.5V
VOUTSU = 3.3V
100
1000
MAX1565 toc06
2.0
1.5
2.5
3.0
3.5
4.0
INPUT VOLTAGE (V)
BUCK-BOOST EFFICIENCY
vs. INPUT VOLTAGE
(3.3V OUTPUT, VOUTSU = 5V)
BOOST AND BUCK-BOOST COMBINED
EFFICIENCY vs. INPUT VOLTAGE
AUX_ EFFICIENCY vs. LOAD CURRENT
(5V OUTPUT)
IOUTSD = 500mA
IOUTSD = 100mA
90
EFFICIENCY (%)
70
100
60
50
40
100
80
70
MAX1565 toc09
80
90
80
70
VIN = 3.6V
VIN = 3V
VIN = 2V
VIN = 1.5V
60
50
40
30
30
VOUTSU = 3.3V, 200mA
VOUTSD = 1.5V, 200mA
EFF% = [(VSUISU) + (VSDISD)]/(VINIIN)
60
VOUTSD = 3.3V
VOUTSU = 5V
10
20
10
2.5
3.0
3.5
1.5
1.0
4.5
4.0
2.0
2.5
3.0
NO-LOAD INPUT CURRENT
vs. INPUT VOLTAGE (SWITCHING)
3.0
BUCK-BOOST
(STEP-UP AND STEP DOWN)
2.5
2.0
STEP-UP
1.0
0.5
100
1000
LOAD CURRENT (mA)
MINIMUM STARTUP VOLTAGE
vs. LOAD CURRENT (OUTSU)
3.5
1.5
10
1
3.5
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
VOUTSD = 1.5V
VOUTSU = 5V
3.5
WITHOUT SCHOTTKY*
MINIMUM STARTUP VOLTAGE (V)
2.0
MAX1565 toc10
1.5
VOUTAUX_ = 5V
0
50
0
3.0
WITH SCHOTTKY*
2.5
2.0
1.5
1.0
0.5
0
MAX1565 toc11
20
INPUT CURRENT (mA)
EFFICIENCY (%)
VOUTSD = 1.5V
VOUTSU = 3.3V
10
LOAD CURRENT (mA)
IOUTSD = 250mA
90
40
LOAD CURRENT (mA)
MAX1565 toc07
100
50
0
10
1
1000
100
60
20
VOUTSD = 3.3V
VOUTSU = 5V
0
10
IOUTSD = 250mA
IOUTSD = 500mA
IOUTSD = 100mA
70
30
10
0
1
80
EFFICIENCY (%)
10
VIN = 4.2V
VIN = 3.6V
VIN = 3V
VIN = 2V
VIN = 1.5V
40
90
MAX1565 toc08
60
80
EFFICIENCY (%)
VIN = 3V
VIN = 2V
VIN = 1.5V
90
EFFICIENCY (%)
80
100
MAX1565 toc05
90
EFFICIENCY (%)
100
MAX1565 toc04
100
70
BUCK-BOOST EFFICIENCY
vs. INPUT VOLTAGE
(1.5V OUTPUT, VOUTSU = 3.3V)
BUCK-BOOST EFFICIENCY
vs. LOAD CURRENT
(3.3V OUTPUT, VOUTSU = 5V)
BUCK-BOOST EFFICIENCY
vs. LOAD CURRENT
(1.5V OUTPUT, VOUTSU = 3.3V)
*SCHOTTKY DIODE CONNECTED
FROM IN TO OUTSU
0
1
2
3
INPUT VOLTAGE (V)
4
5
0
300
600
900
1200
LOAD CURRENT (mA)
_______________________________________________________________________________________
7
MAX1565
Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
REFERENCE VOLTAGE
vs. TEMPERATURE
REFERENCE VOLTAGE
vs. REFERENCE LOAD CURRENT
1.246
1.245
1.244
1.243
1.249
1.248
1.247
1.246
1.242
1.245
1.241
1.240
-25
0
25
50
75
100
100
150
200
500
400
300
200
250
1
10
WHEN THIS DUTY CYCLE IS EXCEEDED FOR
100,000 CLOCK CYCLES, THE MAX1565
SHUTS DOWN
100
ROSC (kΩ)
STEP-UP STARTUP RESPONSE
MAX1565 toc16
MAX1565 toc15
MAXIMUM DUTY CYCLE (%)
COSC = 470pF
COSC = 220pF
COSC = 100pF
COSC = 47pF
600
REFERENCE LOAD CURRENT (µA)
AUX_ MAXIMUM DUTY CYCLE
vs. FREQUENCY
87
700
0
50
0
TEMPERATURE (°C)
88
800
100
1.244
-50
MAX1565 toc14
1.250
REFERENCE VOLTAGE (V)
1.247
900
OSCILLATOR FREQUENCY (kHz)
1.248
OSCILLATOR FREQUENCY vs. ROSC
MAX1565 toc13
1.251
MAX1565 toc12
1.249
REFERENCE VOLTAGE (V)
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
0V
ONSU
5V/div
OUTSU
2V/div
0V
IOUTSU
100mA/div
86
85
84
0A
83
82
COSC = 100pF
IIN
VOUTSO = 3.3V 1A/div
VIN = 2V
0A
81
80
100µs/div
0 100 200 300 400 500 600 700 800 900 1000
FREQUENCY (kHz)
BUCK-BOOST STARTUP RESPONSE
AUX_ STARTUP RESPONSE
MAX1565 toc17
0V
MAX1565 toc18
ONSD = ONSU
5V/div
OUTSU
1V/div
0V
OUTSD
500mA/div
0V
ON1
5V/div
OUT1
2V/div
IOUT1
200mA/div
0V
0V
VOUTSU = 3.3V
VOUTSD = 1.5V
VIN = 2.5V
0A
4ms/div
8
IOUTSD
200mA/div
VOUT1 = 5V
VIN = 2.5V
0A
2ms/div
_______________________________________________________________________________________
1000
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
STEP-UP LOAD TRANSIENT RESPONSE
STEP-DOWN LOAD TRANSIENT RESPONSE
MAX1565 toc19
MAX1565 toc20
IOUTSD
100mA/div
IOUTSU
200mA/div
0A
0A
0V
VOUTSU = 3.3V
VIN = 2.5V
VOUTSU
AC-COUPLED
100mV/div
0V
VOUTSD = 1.5V
VOUTSU = 3.3V
VIN = 2.5V
400µs/div
VOUTSD
AC-COUPLED
50mV/div
400µs/div
Pin Description
PIN
NAME
FUNCTION
1
COMP1
Auxiliary Controller 1 Compensation Node. Connect a series RC from COMP1 to GND to 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 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.
2
FB1
3
PGNDA
4
LXSD
Step-Down Converter Power-Switching Node. Connect LXSD to the step-down 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 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.
6
ONSD
Step-Down Converter On/Off Control Input. Drive ONSD high to turn on the step-down converter. This pin
has an internal 330kΩ pulldown resistor. ONSD does not start until OUTSU is in regulation.
7
Power Ground. Connect PGNDA and PGNDB together and to GND with short trace as close to the IC as
possible.
Step-Down Converter Compensation Node. Connect a series RC from COMPSD to GND to compensate the
COMPSD control loop. COMPSD is pulled to GND in normal shutdown and during thermal shutdown (see the StepDown Compensation section).
_______________________________________________________________________________________
9
MAX1565
Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
MAX1565
Pin Description (continued)
PIN
NAME
8
FBSD
Step-Down Converter Feedback Input. For a 1.5V output, short FBSELSD to GND and 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
Auxiliary Controller 1 On/Off Control Input. Drive ON1 high to turn on. This pin has an internal 330kΩ
pulldown resistor. ON1 cannot start until OUTSU is in regulation.
10
ON2
Auxiliary Controller 2 On/Off Control Input. Drive ON2 high to turn on. This pin has an internal 330kΩ
pulldown resistor. ON2 cannot start until OUTSU is in regulation.
11
ON3
Auxiliary Controller 3 On/Off Control Input. Drive ON3 high to turn on. This pin has an internal 330kΩ
pulldown resistor. ON3 cannot start until OUTSU is in regulation.
12
ONSU
13
REF
14
10
FBSU
FUNCTION
Step-Up Converter On/Off Control. Drive ONSU high to turn on the step-up converter. All other control pins
are locked out until 2ms after the step-up output has reached its final value. This pin has an internal 330kΩ
resistance to GND.
Reference Output. Bypass REF to GND with a 0.1µF or greater capacitor. The 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 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.
15
Step-Up Converter Compensation Node. Connect a series RC from COMPSU to GND to compensate the
COMPSU control loop. COMPSD is pulled to GND in normal shutdown and during thermal shutdown (see the StepDown Compensation section).
16
FBSELSU
Step-Up Feedback Select Pin. With FBSELSU = GND, OUTSU regulates to 3.35V. With FBSELSU = OUTSU,
FBSU regulates to a 1.25V threshold for use with external feedback resistors. This pin is high impedance in
shutdown.
17
FBSELSD
Step-Down Feedback Select Pin. With FBSELSD = GND, FBSD regulates to 1.5V. With FBSELSD = OUTSU,
FBSD regulates to 1.25V for use with external feedback resistors. This pin is high impedance in shutdown.
18
FBSEL1
Auxiliary Controller 1 Feedback Select Pin. With FBSEL1 = GND and FB1 regulates to 5V. With FBSEL1 =
OUTSU, FB1 regulates to 1.25V for use with external feedback resistors. This pin is high impedance in
shutdown.
19
OSC
20
PGNDB
21
LXSU
22
OUTSUA
23
SDOK
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 pin is high impedance in shutdown.
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.
______________________________________________________________________________________
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
PIN
NAME
FUNCTION
24
COMP3
25
FB3
Auxiliary Controller 3 Feedback Input. Connect a resistive voltage-divider from the output voltage to FB3 to
GND. The FB3 feedback threshold is 1.25V. This pin is high impedance in shutdown.
26
OUTSUB
Step-Up Converter Output. OUTSUB powers the MAX1565 and is the sense input when FBSELSU is GND
and the output is 3.3V. Connect OUTSUA to OUTSUB.
27
DL3
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.
28
DL2
Auxiliary Controller 2 Gate-Drive Output. Connect the gate of an N-channel MOSFET to DL2. DL2 swings
from GND to OUTSU and supplies up to 500mA. DL2 is driven to GND in shutdown and thermal limit.
29
DL1
Auxiliary Controller 1 Gate-Drive Output. Connect the gate of an N-channel MOSFET to 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.
31
COMP2
32
FB2
Auxiliary Controller 2 Feedback Input. Connect a resistive voltage-divider from the 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
EP
Exposed Underside Metal Pad. This pad must be soldered to the PC board to achieve package thermal and
mechanical ratings. The exposed pad is electrically connected to GND.
Auxiliary Controller 3 Compensation Node. Connect a series resistor-capacitor from COMP3 to GND to
compensate the control loop. COMP3 is actively driven to GND in shutdown and thermal limit.
Auxiliary Controller 2 Compensation Node. Connect a series resistor-capacitor from COMP2 to GND to
compensate the control loop. COMP2 is actively driven to GND in shutdown and thermal limit.
______________________________________________________________________________________
11
MAX1565
Pin Description (continued)
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
VIN
+1.5V TO +4.2V
-7.5V 20mA
-CCD BIAS
1µF
20µF
2µH
T1
MAX1565
5V
500mA
AUX1
DL1 V-MODE
STEP-UP
PWM
20µF
AUX3
V-MODE DL3
STEP-UP
PWM
FB3
FB1
90.9kΩ
1MΩ
+15V 20mA
+CCD BIAS
1µF
REF
0.1
µF
+1.25V
REF
TO
OUTSU
TO VIN
1µF
4.7µH
AUX2 V-MODE
DL2
STEP-UP
PWM
+15V 100mA
LCD
10µF
36.5kΩ
1MΩ
FB2
90.9kΩ
OSC
100pF
OUTSUB
COMPSU
COMPSD
COMP1
COMP2 CURRENTCOMP3 MODE
STEP-UP
47kΩ
25kΩ
20kΩ
6800pF
10kΩ
3300pF
OUTSUA
LXSU
3.3µH
TO VIN
1µF
10kΩ
0.01µF
3.35V
600mA
MAIN SYSTEM
47µF
PGNDB
FBSU
1000pF
1000pF
INSD
ONSU
ONSD
ON1
ON2
ON3
FBSELSU
FBSELSD
10µF
CURRENTMODE
STEPDOWN
LXSD
4.7µH
22µF
+1.5V
350mA
CORE
PGNDA
FBSD
SDOK
FBSEL1
GND
Figure 1. Typical Application Circuit
12
______________________________________________________________________________________
TO VIN TO
STEP-DOWN
DIRECT
FROM
BATTERY
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
MAX1565
INTERNAL
POWER
OK
VOUTSU
NORMAL
MODE
STARTUP
OSCILLATOR
2.35V
ONSU
VREF
REFOK
DIE OVER
TEMP
1V
ONSU
FLTALL
100,000
CLOCK CYCLE
FAULT TIMER
FAULT
IN
TO INTERNAL
POWER
CLK
OUTSUB
OSC
REF
1.25V
REFERENCE
REF
300ns
ONE-SHOT
GND
COMPSU
OUTSUA
FBSU
FAULT
STEP-UP
TIMER
DONE
(SUSSD)
STARTUP
TIMER
CURRENTMODE
DC-TO-DC
STEP-UP
LXSU
TO
VREF
PGND
ONSU
FLTALL
COMPSD
INSD
FBSD
FAULT
SOFT-START
RAMP
GENERATOR
ONSD
CURRENTMODE
DC-TO-DC
STEP-DOWN
TO
VREF
LXSD
PGND
SUSSD
FLTALL
SDOK
COMP_
FB_
FAULT
SOFT-START
RAMP
GENERATOR
ON_
TO
VREF
ONE OF 3
VOLTAGE-MODE
DC-TO-DC
CONTROLLERS
AUX_
DL_
SUSSD
FLTALL
Figure 2. MAX1565 Functional Diagram
______________________________________________________________________________________
13
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
Detailed Description
The MAX1565 is a complete digital still camera powerconversion IC. It can accept input from a variety of
sources including single-cell Li+ batteries, 2-cell alkaline
or NiMH batteries, as well as systems designed to accept
both battery types. The MAX1565 includes five DC-to-DC
converter channels to generate all required voltages:
1) Synchronous rectified step-up DC-to-DC converter with on-chip MOSFETs—This typically supplies 3.3V for main system power.
2) Synchronous rectified step-down DC-to-DC converter with on-chip MOSFETs—Powering the stepdown from the step-up output provides efficient (up
to 90%) buck-boost functionality that supplies a regulated output when the battery voltage is above or
below the output voltage. The step-down can also
be powered from the battery.
3) Auxiliary DC-to-DC Controller 1—Typically used
for 5V output for motor, strobe, or other functions as
required.
4) Auxiliary DC-to-DC Controller 2—Typically supplies LCD bias voltages with either a multi-output
flyback transformer, or boost converter with chargepump inverter. Alternately may power white LEDs
for LCD backlighting.
5) Auxiliary DC-to-DC Controller 3—Typically supplies CCD bias voltages with either a multi-output
flyback transformer, or boost converter with chargepump inverter.
The MAX1565 can also operate with MAX1801 slave DCto-DC controllers if additional DC-to-DC converter channels are required. All MAX1565 DC-to-DC converter
channels employ fixed-frequency PWM operation.
In addition to multiple DC-to-DC channels, the
MAX1565 also includes overload protection, soft-start
circuitry, adjustable PWM operating frequency, and a
power-OK (POK) output to signal when the step-down
converter output voltage (for CPU core) is in regulation.
Step-Up DC-to-DC Converter
The step-up DC-to-DC converter channel generates a
2.7V to 5.5V output voltage range from a 0.9V to 5.5V
battery input voltage. An internal switch and synchronous rectifier allow conversion efficiencies as high as
95% while reducing both circuit size and the number of
external components. Under moderate to heavy loading,
the converter operates in a low-noise PWM mode with
constant frequency. Switching harmonics generated by
fixed-frequency operation are consistent and easily
filtered.
14
The step-up is a current-mode PWM. An error signal (at
COMPSU) represents the difference between the feedback voltage and the reference. The error signal programs the inductor current to regulate the output voltage.
At light loads (under 75mA when boosting from 2V to
3.3V), efficiency is enhanced by an idle mode in which
switching occurs only as needed to service the load. In
this mode, the inductor current peak is limited to typically
200mA for each pulse.
Step-Down DC-to-DC Converter
The step-down DC-to-DC converter channel is optimized for generating output voltages down to 1.25V.
Lower output voltages can be set by adding an additional resistor (see the Applications Information section). An internal switch and synchronous rectifier allow
conversion efficiencies as high as 95% while reducing
both circuit size and the number of external components. Under moderate to heavy loading, the converter
operates in a low-noise PWM mode with constant frequency. Switching harmonics generated by fixed-frequency operation are consistent and easily filtered.
The step-down is a current-mode PWM. An error signal
(at COMPSD) represents the difference between the
feedback voltage and the reference. The error signal programs the inductor current to regulate the output voltage.
At light loads (under 120mA), efficiency is enhanced by
an idle mode in which switching occurs only as needed
to service the load. In this mode, the inductor current
peak is limited to 150mA (typ) for each pulse.
The step-down remains inactive until the step-up DCto-DC is in regulation. This means that the step-down
DC-to-DC on/off pin (ONSD) is overridden by ONSU.
The soft-start sequence for the step-down begins 1024
OSC cycles after the step-up output is in regulation. If
the step-up, step-down, or any of the auxiliary controllers remains faulted for 200ms, all channels turn off.
The step-down also features an open-drain SDOK output that goes low when the output is in regulation.
Buck-Boost Operation
The step-down input can be powered from the output of
the step-up. By cascading these two channels, the stepdown output can maintain regulation even as the battery
voltage falls below the step-down output voltage. This is
especially useful when trying to generate 3.3V from 1-cell
Li+ inputs, or 2.5V from 2-cell alkaline or NiMH inputs, or
when designing a power supply that must operate from
both Li+ and alkaline/NiMH inputs. Compound efficiencies of up to 90% can be achieved when the step-up and
step-down are operated in series.
______________________________________________________________________________________
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
Direct Battery Step-Down Operation
The step-down converter can also be operated directly
from the battery as long as the voltage at INSD does
not exceed OUTSU by more than a Schottky diode forward voltage. When using this connection, connect a
Schottky diode from the battery input to OUTSU. There
is also an internal 10kΩ resistance from OUTSU to
INSD, which adds a small additional current drain (of
approximately (V OUTSU - V INSD)/10kΩ from OUTSU
when INSD is not connected directly to OUTSU.
Step-down direct battery operation improves efficiency
for the step-down output (up to 95%), but limits the
upper limit of the output voltage to 200mV less than the
minimum battery voltage. In 1-cell Li+ designs (with a
2.7V min), the output can be set up to 2.5V. In 2-cell
alkaline or NiMH designs, the output may be limited to
1.5V or 1.8V, depending on the minimum allowed cell
voltage.
Auxiliary DC-to-DC Controllers
The three auxiliary controllers operate as fixed-frequency
voltage-mode PWM controllers. They do not have
internal MOSFETs, so output power is determined by
external components. The controllers regulate output
voltage by modulating the pulse width of the DL_ drive
signal to an external N-channel MOSFET switch.
Figure 3 shows a functional diagram of an AUX
controller channel. A sawtooth oscillator signal at OSC
governs timing. At the start of each cycle, DL_ goes
high, turning on the external N-FET switch. The switch
then turns off when the internally level-shifted sawtooth
rises above COMP_ or when the maximum duty cycle is
exceeded. The switch remains off until the start of the
next cycle. A transconductance error amplifier forms an
integrator at COMP_ so that DC high-loop gain and
accuracy can be maintained.
The auxiliary controllers do not start until the step-up
DC-to-DC output is in regulation. If the step-up, stepdown, or any of the auxiliary controllers remains faulted
for 100,000 OSC cycles, then all MAX1565 channels
latch off.
The step-down can only be briefly operated in dropout
since the MAX1565 fault protection detects the out-ofregulation condition and activates after 100,000 OSC
cycles, or 200ms at 500kHz. At that point, all MAX1565
channels shut down.
FB
COMP
R
Q
DL_
LEVEL
SHIFT
REFI
SOFTSTART*
REF
S
0.85 REF
CLK
OSC
*SOFT-START RAMPS REFI FROM 0V TO VREF IN 4096 CLOCK CYCLES.
FAULT
PROTECTION
ENABLE
Figure 3. PWM Auxiliary Controller Functional Diagram
______________________________________________________________________________________
15
MAX1565
Note that the step-up output supplies both the step-up
load and the step-down input current when the stepdown is powered from the step-up. The step-down
input current reduces the available step-up output current for other loads.
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
Maximum Duty Cycle
The MAX1565 auxiliary PWM controllers have a guaranteed maximum duty cycle of 80%. That is to say that all
controllers can achieve at least 80% and typically
reach 85%. In boost designs that employ continuous
current, the maximum duty cycle limits the boost ratio
such that:
1 - VIN/VOUT ≤ 80%
With discontinuous inductor current, no such limit exists
for the input/output ratio since the inductor has time to
fully discharge before the next cycle begins.
Master/Slave Configurations
The MAX1565 supports MAX1801 slave PWM controllers that obtain input power, a voltage reference,
and an oscillator signal directly from the MAX1565
master. The master/slave configuration allows channels
to be easily added and minimizes system cost by eliminating redundant circuitry. The slaves also control the
harmonic content of noise since their operating frequency is synchronized to that of the MAX1565 master
converter. A MAX1801 connection to the MAX1565 is
shown in Figure 11.
Fault Protection
The MAX1565 has robust fault and overload protection.
After power-up, the device is set to detect an out-of
regulation state that could be caused by an overload or
short. If any DC-to-DC converter channel (step-up,
step-down, or any of the auxiliary controllers) remains
faulted for 100,000 clock cycles, then ALL outputs latch
off until the step-up DC-to-DC converter is reinitialized
by the ONSU pin, or by cycling of input power. The
fault-detection circuitry for any channel is disabled during its initial turn-on soft-start sequence.
Note that output of the step-up, or that of any auxiliary
channel set up in boost configuration, does not fall to
0V during shutdown or fault. This is due to the current
path from the battery to the output that remains even
when the channel is off. This path exists through the
boost inductor and the synchronous rectifier body diode.
An auxiliary boost channel falls to the input voltage
minus the rectifier drop during fault and shutdown.
OUTSU falls to the input voltage minus the synchronous
rectifier body diode drop during shutdown, and also
during fault if the input voltage exceeds 2.5V. If the
input voltage is less than 2.5V, OUTSU remains at 2.5V
due to operation of the startup oscillator, but can
source only limited current.
Reference
The MAX1565 has an internal 1.250V reference.
Connect a 0.1µF ceramic bypass capacitor from REF to
GND within 0.2in (5mm) of the REF pin. REF can source
up to 200µA and is enabled whenever ONSD is high
and OUTSD is above 2.5V. The auxiliary controllers and
MAX1801 slave controllers (if connected) each sink up
to 30µA REF current during startup. If the application
requires that REF be loaded beyond 200µA, it may be
buffered with a unity-gain amplifier or op amp.
Oscillator
All MAX1565 DC-to-DC converter channels employ
fixed-frequency PWM operation. The operating frequency is set by an RC network at the OSC pin. The
range of usable settings is 100kHz to 1MHz. When
MAX1801 slave controllers are added, they operate at
the same frequency set by OSC.
The oscillator uses a comparator, a 300ns one-shot,
and an internal N-FET switch in conjunction with an
external timing resistor and capacitor (Figure 4). When
the switch is open, the capacitor voltage exponentially
approaches the step-up output voltage from zero with a
time constant given by the ROSCCOSC product. The
comparator output switches high when the capacitor
voltage reaches VREF (1.25V). In turn, the one-shot activates the internal MOSFET switch to discharge the
capacitor within a 300ns interval, and the cycle repeats.
Note that the oscillation frequency changes as the main
output voltage ramps upward following startup. The
oscillation frequency is constant once the main output
is in regulation.
VOUTSU
ROSC
OSC
COSC
VREF
(1.25V)
300ns
ONE-SHOT
MAX1565
Figure 4. Master Oscillator
16
______________________________________________________________________________________
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
Soft-Start
The MAX1565 step-down and AUX_ channels feature a
soft-start function that limits inrush current and prevents
excessive battery loading at startup by ramping the
output voltage to the regulation voltage. This is
achieved by increasing the internal reference inputs to
the controller transconductance amplifiers from 0V to
the 1.25V reference voltage over 4096 oscillator cycles
(8ms at 500kHz) when initial power is applied or when
a channel is enabled. Soft-start is not included in the
step-up converter in order to avoid limiting startup
capability with loading.
Shutdown
The step-up converter is activated with a high input at
ONSU. The step-down and auxiliary DC-to-DC converters 1, 2, and 3 activate with a high input at ONSD,
ON1, ON2, and ON3, respectively. The auxiliary controllers and step-down cannot be activated until
OUTSU is in regulation. For automatic startup, connect
ON_ to OUTSU or a logic level greater than 1.6V.
Design Procedure
Setting the Switching Frequency
Choose a switching frequency to optimize external
component size or circuit efficiency for any particular
MAX1565 application. Typically, switching frequencies
between 300kHz and 600kHz offer a good balance
between component size and circuit efficiency. Higher
frequencies generally allow smaller components and
lower frequencies give better conversion efficiency.
The switching frequency is set with an external timing
resistor (ROSC) and capacitor (COSC). At the beginning
of a cycle, the timing capacitor charges through the
resistor until it reaches VREF. The charge time, t1, is:
t1 = -ROSCCOSC ln [1 - 1.25/VOUTSU]
Table 1. Voltage Setting Summary
CHANNEL FB_
FB THRESHOLD
(FBSEL_ LOW)
FBSU
3.35V
FBSD
1.5V
FB1
FB2
FB2
FB THRESHOLD
(FBSEL_ HIGH)
1.25V
5V
Always 1.25V
(FBSEL is not provided for these channels)
The capacitor voltage is then given time (t2 = 300ns) to
discharge. The oscillator frequency is
fOSC = 1/(t1 + t2)
fOSC can operate from 100kHz to 1MHz. Choose COSC
between 47pF and 470pF. Determine ROSC from the
equation:
ROSC = (300ns - 1/fOSC)/(COSC ln [1 - 1.25/VOUTSU])
See the Typical Operating Characteristics for fOSC versus
ROSC using different values of COSC.
Setting Output Voltages
The MAX1565 step-up/step-down converters and the
AUX1 controllers have both factory-set and adjustable
output voltages. These are selected by FBSEL_ for the
appropriate channel. When FBSEL_ is low, the channel
output regulates at its preset voltage. When FBSEL_ is
high, the channel regulates FB_ at 1.25V for use with
external feedback resistors.
When setting the voltage for auxiliary channels 2 and 3,
or when using external feedback at FBSU, FBSD, or FB1,
connect a resistive voltage-divider from the output voltage to the corresponding FB_ input. The FB_ input bias
current is less than 100nA, so choose the low-side (FB_to-GND) resistor (RL), to be 100kΩ or less. Then calculate the high-side (output-to-FB_) resistor (RH) using:
RH = RL [(VOUT/1.25) - 1]
General Filter Capacitor Selection
The input capacitor in a DC-to-DC converter reduces
current peaks drawn from the battery, or other input
power source, and reduces switching noise in the controller. The impedance of the input capacitor at the
switching frequency should be less than that of the
input source so that high-frequency switching currents
do not pass through the input source.
______________________________________________________________________________________
17
MAX1565
Low-Voltage Startup Oscillator
The MAX1565 internal control and reference-voltage
circuitry receive power from OUTSU and do not function
when OUTSU is less than 2.5V. To ensure low-voltage
startup, the step-up employs a low-voltage startup
oscillator that activates at 0.9V. The startup oscillator
drives the internal N-channel MOSFET at LXSU until
OUTSU reaches 2.5V, at which point voltage control is
passed to the current-mode PWM circuitry.
Once in regulation, the MAX1565 operates with inputs
as low as 0.7V since internal power for the IC is supplied by OUTSU. At low input voltages, the MAX1565
can have difficulty starting into heavy loads.
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
The output capacitor keeps output ripple small and
ensures control-loop stability. The output capacitor
must also have low impedance at the switching frequency. Ceramic, polymer, and tantalum capacitors
are suitable, with ceramic exhibiting the lowest ESR
and high-frequency impedance.
Output ripple with a ceramic output capacitor is
approximately:
VRIPPLE = IL(PEAK) [1/(2π fOSC COUT)]
If the capacitor has significant ESR, the output ripple
component due to capacitor ESR is:
VRIPPLE(ESR) = IL(PEAK) ESR
Output capacitor specifics are also discussed in the
Step-Up Compensation section and the Step-Down
Compensation section.
Step-Up Component Selection
The external components required for the step-up are
an inductor, input and output filter capacitor, and compensation RC. Typically, the inductor is selected to
operate with continuous current for best efficiency. An
exception might be if the step-up ratio, (VOUT/VIN), is
greater than 1/(1 - DMAX), where DMAX is the maximum
PWM duty factor of 80%.
When using the step-up channel to boost from a low input
voltage, loaded startup is aided by connecting a
Schottky diode from the battery to OUTSU. See the
Minimum Startup Voltage vs. Load Current graph in the
Typical Operating Characteristics.
Step-Up Inductor
In most step-up designs, a reasonable inductor value
(LIDEAL) can be derived from the following equation,
which sets continuous peak-to-peak inductor current at
one-half the DC inductor current:
LIDEAL = [2 VIN(MAX) D(1 - D)] / (IOUT fOSC)
where D is the duty factor given by:
D = 1 - (VIN / VOUT)
Given LIDEAL, the consistent peak-to-peak inductor current is 0.5 I OUT /(1 - D). The peak inductor current,
IIND(PK) = 1.25 IOUT / (1 - D). Inductance values smaller
than L IDEAL can be used to reduce inductor size.
However, if much smaller values are used, the inductor
current rises and a larger output capacitance may be
required to suppress output ripple.
18
Step-Up Compensation
The inductor and output capacitor are usually chosen
first in consideration of performance, size, and cost. The
compensation resistor and capacitor are then chosen to
optimize control-loop stability. In some cases it may help
to readjust the inductor or output capacitor value to get
optimum results. For typical designs, the component
values in the circuit of Figure 1 yield good results.
The step-up converter employs current-mode control,
thereby simplifying the control-loop compensation.
When the converter operates with continuous inductor
current (typically the case), a right-half-plane zero
(RHPZ) appears in the loop-gain frequency response.
To ensure stability, the control-loop gain should
crossover (drop below unity gain) at a frequency (fC)
much less than that of the right-half-plane zero.
The relevant characteristics for step-up channel compensation are:
1) Transconductance (from FBSU to COMPSU), gmEA
(135µS)
2) Current-sense amplifier transresistance, R CS ,
(0.3V/A)
3) Feedback regulation voltage, VFB (1.25V)
4) Step-up output voltage, VSUOUT, in V
5) Output load equivalent resistance, R LOAD ,
in Ω = VSUOUT/ILOAD
The key steps for step-up compensation are:
1) Place fC sufficiently below the RHPZ and calculate CC.
2) Select RC based on the allowed load-step transient. RC sets a voltage delta on the COMP pin that
corresponds to load current step.
3) Calculate the output filter capacitor (C OUT )
required to allow the RC and CC selected.
4) Determine if CP is required (if calculated to be >
10pF).
For continuous conduction, the right-plane zero frequency (fRHPZ) is given by:
fRHPZ = VOUTSU (1 - D)2 / (2π L ILOAD)
where D = the duty cycle = 1 - (VIN/VOUT), L is the
inductor value, and ILOAD is the maximum output current. Typically target crossover (fC) for 1/6 the RHPZ.
For example, if we assume VIN = 2V, VOUT = 3.35V,
and I OUT = 0.5A, then R LOAD = 6.7Ω. If we select
L = 3.3µH then:
fRHPZ = 3.35 (2/3.35)2 / (2π x 4.7 x 10-6 x 0.5) = 115kHz
______________________________________________________________________________________
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
Choose 6.8nF. Now select RC such that transient droop
requirements are met. For example, if 4% transient
droop is allowed, the input to the error amplifier moves
0.04 x 1.25V, or 50mV. The error amp output drives
50mV x 135µS, or 6.75µA, across RC to provide transient gain. Since the current-sense transresistance is
0.3V/A, the value of RC that allows the required load
step swing:
RC = 0.3 IIND(PK)/6.75µA
In a step-up DC-to-DC converter, if LIDEAL is used, output current relates to inductor current by:
IIND(PK) = 1.25 IOUT/(1 - D) = 1.25 IOUT VOUT/VIN
Thus, for a 400mA output load step with VIN = 2V and
VOUT = 3.35V:
RC = [1.25(0.3 x 0.4 x 3.35)/2)]/6.75µA = 37kΩ
Note that the inductor does not limit the response in this
case since it can ramp at 2V/3.3µH, or 606mA/µs. The
output filter capacitor is then chosen so that the COUT
RLOAD pole cancels the RC CC zero:
COUT RLOAD = RCCC
For example:
COUT = 37kΩ x 6.8nF/6.7 = 37.5µF
Since a reasonable value for COUT is 47µF rather than
37.5, choose 47µF and rescale RC:
RC = 47µF x 6.7/6.8nF = 46.3kΩ
which provides a slightly higher transient gain and consequently less transient droop than previously selected.
If the output filter capacitor has significant ESR, a zero
occurs at:
ZESR = 1/(2π COUT RESR)
If ZESR > fC, it can be ignored, as is typically the case
with ceramic output capacitors. If ZESR is less than fC,
it should be cancelled with a pole set by capacitor CP
connected from COMPSU to GND:
CP = COUT RESR/RC
If CP is calculated to be < 10pF, it can be omitted.
Step-Down Component Selection
Step-Down Inductor
The external components required for the step-down
are an inductor, input and output filter capacitors, and
compensation RC network. The MAX1565 step-down
converter provides best efficiency with continuous
inductor current. A reasonable inductor value (LIDEAL)
can be derived from:
LIDEAL = 2 (VIN) D (1 - D)/(IOUT fOSC)
which sets the peak-to-peak inductor current at 1/2 the
DC inductor current. D is the duty cycle:
D = VOUT/VIN
Given LIDEAL, the peak-to-peak inductor current variation is 0.5 IOUT. The absolute peak inductor current is
1.25 IOUT. Inductance values smaller than LIDEAL can
be used to reduce inductor size. However, if much
smaller values are used, inductor current rises and a
larger output capacitance may be required to suppress
output ripple.
Larger values than LIDEAL can be used to obtain higher
output current, but with typically larger inductor size.
Step-Down Compensation
The relevant characteristics for step-down compensation are:
1) Transconductance (from FBSD to COMPSD), gmEA
(135µS)
2) Step-down slope compensation pole, P SLOPE =
VIN / (πL)
3) Current-sense amplifier transresistance, R CS ,
(0.6V/A)
4) Feedback regulation voltage, VFB (1.25V)
5) Step-down output voltage, VSD, in V
6) Output load equivalent resistance, R LOAD ,
in Ω = VOUTSD/ILOAD
The key steps for step-down compensation are:
1) Set the compensation RC zero to cancel the RLOAD
COUT pole.
2) Set the loop crossover below the lower of 1/5 the
slope compensation pole, or 1/5 the switching frequency.
If we assume VIN = 3.35V, VOUT = 1.5V, and IOUT =
350mA, then RLOAD = 4.3Ω.
______________________________________________________________________________________
19
MAX1565
Choose fC = 20kHz. Calculate CC:
CC = (VFB/VOUT)(RLOAD/RCS)(gm/2π fC)(1 - D)
= (1.25/3.35)(6.7/0.3) x (135µS/(6.28 x 20kHz)
(2/3.35) = 5.35nF
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
If we select L = 4.7µH and fOSC = 440kHz, PSLOPE =
VIN/(πL) = 214kHz, so choose fC = 40kHz and calculate CC:
CC = (VFB/VOUT)(RLOAD/RCS)(gm/2π fC)
= (1.25/1.5)(4.3/0.6) x (135µS/(6.28 x 40kHz)
= 3.2nF
Choose 3.3nF. Now select RC such that transient droop
requirements are met. For example, if 4% transient
droop is allowed, the input to the error amplifier moves
0.04 x 1.25V, or 50mV. The error amp output drives
50mV x 135µS, or 6.75µA across RC to provide transient gain. Since the current-sense transresistance is
0.6V/A, the value of RC that allows the required load
step swing:
RC = 0.6 IIND(PK)/6.75µA
In a step-down DC-to-DC converter, if LIDEAL is used,
output current relates to inductor current by:
IIND(PK) = 1.25 IOUT
Thus, for a 250mA output load step with VIN = 3.35V
and VOUT = 1.5V:
RC = (1.25 x 0.6 x 0.25)/6.75µA = 27.8kΩ
Choose 27kΩ. Note that the inductor does not limit the
response in this case since it can ramp at (V IN VOUT)/4.7µH, or (3.35 - 1.5)/4.7µH = 394mA/µs.
The output filter capacitor is then chosen so that the
COUT RLOAD pole cancels the RC CC zero:
COUTRLOAD = RCCC
For example:
COUT = 27kΩ x 3.3nF/4.3 = 20.7µF
Choose 22µF. If the output filter capacitor has significant ESR, a zero occurs at:
ZESR = 1/(2π COUTRESR)
If ZESR > fC, it can be ignored, as is typically the case
with ceramic output capacitors. If ZESR is less than fC,
it should be cancelled with a pole set by capacitor CP
connected from COMPSD to GND:
CP = COUTRESR/RC
If CP is calculated to be < 10pF, it can be omitted.
20
Auxiliary Controller Component Selection
External MOSFET
All MAX1565 auxiliary controllers drive external logiclevel N-channel MOSFETs. Significant MOSFET selection parameters are:
1) On-resistance (RDS(ON))
2) Maximum drain-to-source voltage (VDS(MAX))
3) Total gate charge (QG)
4) Reverse transfer capacitance (CRSS)
DL_ swings between OUTSU and GND. Use a MOSFET
with on-resistance specified at or below the main output
voltage. The gate charge, QG, includes all capacitance
associated with charging the gate and helps to predict
MOSFET transition time between on and off states.
MOSFET power dissipation is a combination of
on-resistance and transition losses. The on-resistance
loss is:
PRDSON = D IL2 RDS(ON)
where D is the duty cycle, IL is the average inductor
current, and RDS(ON) is MOSFET on-resistance. The
transition loss is approximately:
PTRANS = (VOUT IL fOSC tT)/3
where VOUT is the output voltage, IL is the average
inductor current, fOSC is the switching frequency, and
tT is the transition time. The transition time is approximately QG/IG, where QG is the total gate charge, and
IG is the gate drive current (typically 0.5A). The total
power dissipation in the MOSFET is:
PMOSFET = PRDSON + PTRANS
Diode
For most auxiliary applications, a Schottky diode rectifies
the output voltage. The Schottky diode’s low forward voltage and fast recovery time provide the best performance
in most applications. Silicon signal diodes (such as
1N4148) are sometimes adequate in low-current
(<10mA) high-voltage (>10V) output circuits where the
output voltage is large compared to the diode forward
voltage.
Auxiliary Compensation
The auxiliary controllers employ voltage-mode control
to regulate their output voltage. Optimum compensation somewhat depends on whether the design uses
continuous or discontinuous inductor current.
______________________________________________________________________________________
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
To ensure discontinuous operation, the inductor must
have a sufficiently low inductance to fully discharge on
each cycle. This occurs when:
L < [VIN2 (VOUT - VIN)/VOUT3] [RLOAD/(2 fOSC)]
A discontinuous current boost has a single pole at:
fP = (2VOUT - VIN)/(2π RLOADCOUTVOUT)
Choose the integrator capacitor such that the unity-gain
crossover (fC) occurs at fOSC/10 or lower. Note that for
many auxiliary circuits, such as those powering motors,
LEDs, or other loads that do not require fast transient
response, it is often acceptable to overcompensate by
setting fC at fOSC/20 or lower. CC is then determined by:
CC = [2VOUTVIN /((2VOUT - VIN)VRAMP)]
[VOUT /(K(VOUT - VIN))]1/2 [(VFB/VOUT)
(gM /(2π fC))]
where K = 2 L fOSC/RLOAD, and VRAMP is the internal
slope compensation voltage ramp of 1.25V. The CCRC
zero is then used to cancel the fP pole, so:
RC = RLOADCOUTVOUT/[(2VOUT - VIN) CC]
Continuous Inductor Current
Continuous inductor current can sometimes improve
boost efficiency by lowering the ratio between peak
inductor current and output current. It does this at the
expense of a larger inductance value that requires larger
size for a given current rating. With continuous inductor
current boost operation, there is a right-plane zero at:
fRHPZ = (1 - D)2 RLOAD /(2πL)
where (1 - D) = VIN/VOUT (in a boost converter). A complex pole pair is located at:
f0 = VOUT/[2π VIN (L COUT)1/2]
If the zero due to the output capacitor capacitance and
ESR is less than 1/10 the right-plane zero:
ZCOUT = 1/(2π COUT RESR) < fRHPZ/10
Choose C C such that the crossover frequency f C
occurs at ZCOUT. The ESR zero provides a phase boost
at crossover.
CC = (VIN/VRAMP)(VFB/VOUT)(gM /(2π ZCOUT))
Choose RC to place the integrator zero, 1/(2π RCCC), at
f0 to cancel one of the pole pairs:
RC = VIN (L COUT)1/2/(VOUT CC)
If ZCOUT is not less than fRHPZ/10 (as is typical with
ceramic output capacitors) and continuous conduction is
required, then cross the loop over before fRHPZ and f0:
fC < f0/10, and fC < fRHPZ/10
In that case:
CC = (VIN/VRAMP)(VFB/VOUT)(gM /(2π fC))
Place 1/(2π RCCC) = 1/(2π RLOADCOUT), so that RC =
RLOAD COUT/CC or reduce the inductor value for discontinuous operation.
Applications Information
LED, LCD, and Other Boost Applications
Any auxiliary channel can be used for a wide variety of
step-up applications. These include generating 5V or
some other voltage for motor or actuator drive, generating
15V or a similar voltage for LCD bias, or generating a
step-up current source to efficiently drive a series array
of white LEDs for display backlighting. Figures 5 and 6
show examples of these applications.
TO VBATT
4.7µF
4.7µH
15V
100mA
22µF
OUTSU
DL_
1.1MΩ
FB_
100kΩ
AUX_
PWM
MAX1565
(PARTIAL)
Figure 5. Using an AUX_ Controller Channel to Generate LCD
Bias
______________________________________________________________________________________
21
MAX1565
Discontinuous Inductor Current
When the inductor current falls to zero on each switching
cycle, it is described as discontinuous. The inductor is
not utilized as efficiently as with continuous current. This
often has little negative impact in light-load applications
since the coil losses may already be low compared to
other losses. A benefit of discontinuous inductor current is more flexible loop compensation and no maximum duty-cycle restriction on boost ratio.
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
TO VBATT
INPUT
1-CELL
Li+
1µF
10µH
MAIN
OUTSU
1µF
IN
WHITE
LEDs
L2
L1
DL_
AUX_
PWM
OUTPUT
3.3V
DCON
DL
FB_
D1
C2
Q1
PART OF
MAX1565
R1
FB
62Ω
(FOR 20mA)
MAX1565
(PARTIAL)
Figure 6. AUX_ Channel Powering a White LED Step-Up
Current Source
SEPIC Buck-Boost
The MAX1565’s internal switch step-up and step-down
can be cascaded to make a high-efficiency buck-boost
converter, but it may sometimes be desirable to build a
second buck-boost converter with an AUX_ controller.
One type of step-up/step-down converter is the SEPIC
(Figure 7). Inductors L1 and L2 can be separate inductors or wound on a single core and coupled like a
transformer. Typically, a coupled inductor improves
efficiency since some power is transferred through the
coupling, causing less power to pass through the coupling capacitor (C2). Likewise, C2 should have low ESR
to improve efficiency. The ripple current rating must be
greater than the larger of the input and output currents.
The MOSFET (Q1) drain-to-source voltage rating, and
the rectifier (D1) reverse-voltage rating must exceed
the sum of the input and output voltages. Other types of
step-up/step-down circuits are a flyback converter and
a step-up converter followed by a linear regulator.
Multiple Output Flyback Circuits
Some applications require multiple voltages from a single
converter channel. This is often the case when generating
voltages for CCD bias or LCD power. Figure 8 shows a
two-output flyback configuration with AUX_. The
controller drives an external MOSFET that switches the
transformer primary. Two transformer secondaries
generate the output voltages. Only one positive output
voltage can be fed back, so the other voltages are set
by the turns ratio of the transformer secondaries. The
load stability of the other secondary voltages depends
on transformer leakage inductance and winding resistance. Voltage regulation is best when the load on the
22
R2
Figure 7. Auxiliary SEPIC Configuration
secondary that is not fed back is small when compared
to the load on the one that is. Regulation also improves
if the load current range is limited. Consult the transformer manufacturer for the proper design for a given
application.
Boost with Charge Pump for Positive and
Negative Outputs
Negative output voltages can be produced without a
transformer, using a charge-pump circuit with an auxiliary controller as shown in Figure 9. When MOSFET Q1
turns off, the voltage at its drain rises to supply current
to VOUT+. At the same time, C1 charges to the voltage
VOUT+ through D1.
TO VBATT
1µF
1µF
+15V
30mA
CCD+
1.1MΩ
100kΩ
AUX_
PWM
1µF
OUTSU
DL_
-7.5V
20mA
CCD*(SEE NOTE)
FB_
MAX1565
(PARTIAL)
*LOAD RESISTOR REQUIRED IF -7.5V
OPERATES WITH NO LOAD
Figure 8. +15V and -7.5V CCD Bias with Transformer
______________________________________________________________________________________
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
D2
TO VBATT
VOUT+
+15V
20mA
C2
1µF
1µF
R1
1MΩ
FB_
AUX_
PWM
OUTSU
Q1
DL_
C1
1µF
R2
90.9kΩ
D3
C3
1µF
D1
VOUT-15V
10mA
Adding a MAX1801 Slave
The MAX1801 is a 6-pin SOT slave DC-to-DC controller
that can be connected to generate additional output
voltages. It does not generate its own reference or
oscillator. Instead, it uses the reference and oscillator
of the MAX1565 (Figure 11). The MAX1801 controller
operation and design are similar to that of a MAX1565
AUX controller. All comments in the Auxiliary Controller
Component Selection section also apply to add-on
MAX1801 slave controllers. For more details, refer to
the MAX1801 data sheet.
MAX1565
(PARTIAL)
Figure 9. ±15V Output Using a Boost with Charge-Pump
Inversion
10µH
+15V
20mA
TO VBATT
1µF
1µF
1MΩ
FB_
AUX_
PWM
90.9kΩ
OUTSU
Q1
1µF
-7.5V
20mA
DL_
1µF
110kΩ
1µF
MAX1565
(PARTIAL)
549kΩ
IN
SHDN
GND
OUT
FB_
+1.25V
MAX1616
Figure 10. +15V and -7.5V CCD Bias without Transformer
______________________________________________________________________________________
23
MAX1565
L1
10µH
When the MOSFET turns on, C1 discharges through
D3, thereby charging C3 to V OUT - minus the drop
across D3 to create roughly the same voltage as
VOUT+ at VOUT- but with inverted polarity.
If different magnitudes are required for the positive and
negative voltages, a linear regulator can be used at
one of the outputs to achieve the desired voltages. One
such connection is shown in Figure 10. This circuit is
somewhat unique in that a positive output linear regulator is able to regulate the negative output. It does this
by controlling the charge to the flying capacitor rather
than directly regulating at the output.
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
TO BATT
OUTSU
VOUT
DL
IN
OSC
MAX1801 OSC
MAX1565
(PARTIAL)
FB
COMP
GND
REF
REF
DCON
Figure 11. Connecting the MAX1801 Slave PWM Controller to the MAX1565
Using SDOK for Power Sequencing
SDOK goes low when the step-down reaches regulation. Some microcontrollers with low-voltage cores
require that the high-voltage (3.3V) I/O rail not be
powered up until the core has a valid supply. The
circuit in Figure 12 accomplishes this by driving the
gate of a PFET connected between the 3.3V output and
the microcontroller I/O supply. Alternately, power
sequencing may be implemented by connecting RC
networks to the appropriate converter ON_ inputs.
MAX1565
(PARTIAL)
OUTSUB
OUTSUA
LXSU
STEP-UP
Setting OUTSD Below 1.25V
where VSD is the output voltage, VFBSD is 1.25V, and
VSU is the step-up output voltage. Note that any available voltage that is higher than 1.25V can be used as
the connection point for R3 in Figure 13 and for the VSD
term in the equation. Since there are multiple solutions
for R1, R2, and R3, the above equation cannot be written in terms of one resistor. The best method for determining resistor values is to enter the above equation
into a spreadsheet and test estimated resistors’ values.
A good starting point is with 100kΩ at R2 and R3.
24
10µH
3.3V
TO
CPU
10µF
The step-down feedback voltage is 1.25V when
FBSELSD is high. With a standard two-resistor feedback network, the output voltage may be set to values
between 1.25V and the input voltage. If a step-down
output voltage less than 1.25V is desired, it can be set by
adding a third feedback resistor from FB to a voltage
higher than 1.25V (the step-up output is a convenient
voltage for this) as shown in Figure 13.
The equation governing output voltage shown in Figure
13 is:
0 = [(VSD - VFBSD)/R1] + [(0 - VFBSD)/R2]
+ [(VSU - VFBSD)/R3]
3.35V
TO
VBATT
PGNDB
1MΩ
FBSU
1MΩ
SDOK
INSD
TO VBATT
OR OUTSU
10µF
LXSD
STEP-DOWN
4.7µH
VCORE
1.5V
10µF
FBSD
PGNDA
Figure 12. Using SDOK to Gate 3.3V Power to CPU After the
Core Voltage is OK
______________________________________________________________________________________
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
VSU
3.3V
OUTSUA
OUTSUB
FBSELSD
MAX1565
(PARTIAL)
INSD
10µF
LXSD
CURRENT-MODE
STEP-DOWN
4.7µH
VSD
0.8V
22µF
PGNDA
FBSD
R3
100kΩ
VFBSD
1.25V
R1
56kΩ
R2
100kΩ
Figure 13. Setting OUTSD for Outputs Below 1.25V
Chip Information
TRANSISTOR COUNT: 9420
PROCESS: BiCMOS
______________________________________________________________________________________
25
MAX1565
Designing a PC Board
Good PC board layout is important to achieve optimal
performance from the MAX1565. Poor design can
cause excessive conducted and/or radiated noise.
Conductors carrying discontinuous currents, and any
high-current path should be made as short and wide as
possible. A separate low-noise ground plane containing
the reference and signal grounds should connect to the
power-ground plane at only one point to minimize the
effects of power-ground currents. Typically, the ground
planes are best joined right at the IC.
Keep the voltage feedback network very close to the
IC, preferably within 0.2in (5mm) of the FB_ pin. Nodes
with high dV/dt (switching nodes) should be kept as
small as possible and should be routed away from
high-impedance nodes such as FB_. Refer to the
MAX1565EVKIT evaluation kit data sheet for a full PC
board example.
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
D2
0.15 C A
D
b
CL
0.10 M C A B
D2/2
D/2
PIN # 1
I.D.
QFN THIN.EPS
MAX1565
Small, High-Efficiency, Five-Channel
Digital Still Camera Power Supply
k
0.15 C B
PIN # 1 I.D.
0.35x45
E/2
E2/2
CL
(NE-1) X e
E
E2
k
L
DETAIL A
e
(ND-1) X e
CL
CL
L
L
e
e
0.10 C
A
C
0.08 C
A1 A3
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE
16, 20, 28, 32L, QFN THIN, 5x5x0.8 mm
APPROVAL
COMMON DIMENSIONS
DOCUMENT CONTROL NO.
REV.
21-0140
C
1
2
EXPOSED PAD VARIATIONS
NOTES:
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.
3. N IS THE TOTAL NUMBER OF TERMINALS.
4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1
SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE
ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE.
5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm
FROM TERMINAL TIP.
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.
8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.
9. DRAWING CONFORMS TO JEDEC MO220.
10. WARPAGE SHALL NOT EXCEED 0.10 mm.
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE
16, 20, 28, 32L, QFN THIN, 5x5x0.8 mm
APPROVAL
DOCUMENT CONTROL NO.
REV.
21-0140
C
2
2
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
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