NJRC NJU6051KM1 White led driver with automatic dimming control Datasheet

NJU6051
PRELIMINARY
White LED Driver with Automatic Dimming Control
! GENERAL DESCRIPTION
The NJU6051 is a white LED driver with an automatic
dimming control. It contains an output driver, a PWM
controller, a luminance sensor control (power supply for
sensor & A/D converter), a step-up DC/DC converter, a serial
interface, etc.
The output driver ensures a 30mA maximum capability
which allows the connection of 8 white LEDs (4 series x 2
parallels). Depending on the ambient light sensed with an
external luminance sensor, the PWM controller controls
PWM duty in 8 steps preselected out of 64 steps. In addition,
the frequency of the DC/DC converter is high so that it
permits the use of small, low-profile inductors and capacitors
to minimize the footprint in space-conscious applications.
All of these benefits make the NJU6051 suitable for the
battery-powered portable applications such as a cellular
phone, a camcorder, PDA, etc.
! PACKAGE OUTLINE
NJU6051KM1
NJU6051V
! FEATURES
# Drives up to 8 white LEDs (4 series x 2 parallels)
VSW = 18.0V(Max.), IOUT = 30mA
# Built-in PWM Dimming Control
(Selectable 8 out of 64 steps)
# Built-in Luminance Sensor Control (Power Supply for Sensor & A/D converter)
#
#
#
#
#
#
(No MPU-access required after initial setting)
Built-in Temperature Compensation Circuit to Suppress the Characteristic Degradation of LEDs
Uses Small Inductor and Capacitors
1.8V to 3.6V Operating Voltage for Logic Circuits (VDDL)
3.0V to 5.5V Operating Voltage for Step-up Circuits (VDD)
CMOS Technology
Package
: QFN20 / SSOP20
Ver.2003-10-23
-1-
NJU6051
! QFN20 PIN CONNECTIONS (TOP VIEW)
CX
REF
VSS
VSS
VSS
FB
VSO
VOUT
SENS
SW
RSTb
SW
SCK
SW
DATA
REQ
VDDL
VDD
NC
TEST
! SSOP20 PIN CONNECTIONS (TOP VIEW)
SW
VOUT
SW
FB
SW
VSS
TEST
VSS
NC
VSS
VDD
REF
VDDL
REQ
-2-
CX
VSO
DATA
SENS
SCK
RSTb
Ver.2003-10-23
NJU6051
! PIN DESCRIPTION
QFN
No.
SSOP
SYMBOL
TYPE
DESCRIPTIONS
3
6
VDD
Power
VDD Power Supply
- Power supply for step-up voltage
4
7
VDDL
Power
VDDL Power Supply
- Power supply for logic voltage.
- Relation:1.8V ≤ VDDL≤ VDD should be maintained.
18
19
20
1
2
3
SW
Input
Switch
- All these terminals should be connected together.
7
10
SCK
Input
6
9
DATA
Input / Output
1
4
TEST
Output
5
8
REQ
Input
9
12
SENS
Input
8
11
RSTb
Input
17
20
VOUT
Input
16
19
FB
Input
13
14
15
16
17
18
VSS
Power
11
14
CX/TCLK
Input
10
13
VSO
Output
12
15
REF
Input
2
5
NC
-
Ver.2003-10-23
Shift Clock
- Serial data is latched on the rising edge of SCK.
Serial Data
Test
- This terminal must be open.
Data Request
“L” : Writing command data
“H” : Reading sensor data
Luminance Sensor Connection
Reset
- Active “L”.
Output
- This terminal is connected to LED anode.
Feedback
Ground
- All these terminals should be connected together.
Oscillator Capacitor Connection / External Clock Input
VSO Power Supply
- Power supply for luminance sensor
- 2.4V typical
Reference Voltage
- This terminal must be open.
Non Connection
- This terminal must be open.
-3-
NJU6051
! BLOCK DIAGRAM
L1
VDD
D1
SW
VOUT
VSO
Regulator
C1
C2
SENS
A/D
Converter
Register
PWM
Controller
A1
VDDL
REQ
Logic
Serial
Interface
REF
VREF
SCK
DATA
RSTb
CX/TCLK
FB
RLED
A2
Reset
VSS
OSC
TEST
-4-
Ver.2003-10-23
NJU6051
! FUNCTIONAL DESCRIPTONS
(1) LED CURRENT CONTROL
The NJU6051 incorporates the LED current control circuit to regulate the LED current (ILED), which is
programmed by the feedback resistor (RLED) connected between the FB and VSS terminals. The reference voltage
VREF is internally regulated to 0.6V typical and connected to the positive input of the built-in comparator A1.
Formula (1) is used to choose the value of the RLED, as shown below.
RLED =
VREF
I LED
--- Formula (1)
VREF=0.6V (TYP.)
Referring to the block diagram is recommended for understanding the operation of the LED current control.
The ILED is the constant current programmed by the RLED. When the feedback voltage on the FB terminal reaches
above the reference voltage VREF on the REF terminal (i.e., ILED is above the level programmed by RLED), the
output capacitor C2 delivers the ILED. Once the feedback voltage drops below the reference voltage (i.e., ILED
drops below the level programmed by RLED), the comparator A1 detects it and turns on the internal MOS switch,
then the current of the inductor L1 begins increasing. When this switch current reaches 470mA and the
comparator A2 detects it, or when the predetermined switch-on-period expires, the MOS switch is turned off.
The L1 then delivers current to the output through the diode D1 as the inductor current drops. After that, the MOS
switch is turned on again and the switch current increases up to 470mA. This switching cycle continues until the
ILED reaches the level programmed by the RLED, then the ILED is maintained constant.
When the feedback voltage is less than 1/2*VREF, the current limit of the MOS switch is reduced to 330mA
typical. This action reduces the average inductor-current, minimizes the power dissipation and protects the IC
against high current at start-up.
The total forward-voltage of the LEDs must be greater than the power supply voltage VDD, otherwise the
LEDs remain lighting up, being out of control.
(2) OSCILLATOR
The built-in oscillator incorporates a reference power supply, so its frequency is independent from the VDD.
The frequency is varied by the external capacitor CX, as shown in Figure 7.
(3) LUMINANCE SENSOR CONTROL
The luminance sensor control circuits consist of the power supply for sensor and the A/D converter. The A/D
converter senses the voltage on the SENS terminal and selects 1 out of 8 registers (PWM REGISTER 0–7). And
the data in the selected register is reflected to the PWM duty (PWM dimming control). The contents of the
registers can be programmed through the serial interface, in other words, the dimming control is user-settable.
The voltage sense and the register selection are updated at regular intervals, and the interval period is set by
the “DIVIDE” bits. The selected register is held by setting “1” at the “HOLD” bit of the command data.
Ver.2003-10-23
-5-
NJU6051
(4) PWM DIMMING CONTROL
By setting the duty data at “PWM REGISTER” bits, 8 out of 64 registers are assigned to the PWM
REGISTER 0-7. The PWM duty is changed depending on the register selected by the SENS voltage. The relation
between the PWM REGISTER and its duty is shown below.
TABLE 1 PWM DUTY vs. PWM REGISTER
REGISTER
DUTY
REGISTER
0,0,0,0,0,0
OFF
0,1,0,0,0,0
0,0,0,0,0,1
3.13%
0,1,0,0,0,1
0,0,0,0,1,0
4.69%
0,1,0,0,1,0
0,0,0,0,1,1
6.25%
0,1,0,0,1,1
0,0,0,1,0,0
7.81%
0,1,0,1,0,0
0,0,0,1,0,1
9.38%
0,1,0,1,0,1
0,0,0,1,1,0
10.94%
0,1,0,1,1,0
0,0,0,1,1,1
12.50%
0,1,0,1,1,1
0,0,1,0,0,0
14.06%
0,1,1,0,0,0
0,0,1,0,0,1
15.63%
0,1,1,0,0,1
0,0,1,0,1,0
17.19%
0,1,1,0,1,0
0,0,1,0,1,1
18.75%
0,1,1,0,1,1
0,0,1,1,0,0
20.31%
0,1,1,1,0,0
0,0,1,1,0,1
21.88%
0,1,1,1,0,1
0,0,1,1,1,0
23.44%
0,1,1,1,1,0
0,0,1,1,1,1
25.00%
0,1,1,1,1,1
DUTY
26.56%
28.13%
29.69%
31.25%
32.81%
34.38%
35.94%
37.50%
39.06%
40.63%
42.19%
43.75%
45.31%
46.88%
48.44%
50.00%
REGISTER
1,0,0,0,0,0
1,0,0,0,0,1
1,0,0,0,1,0
1,0,0,0,1,1
1,0,0,1,0,0
1,0,0,1,0,1
1,0,0,1,1,0
1,0,0,1,1,1
1,0,1,0,0,0
1,0,1,0,0,1
1,0,1,0,1,0
1,0,1,0,1,1
1,0,1,1,0,0
1,0,1,1,0,1
1,0,1,1,1,0
1,0,1,1,1,1
DUTY
51.56%
53.13%
54.69%
56.25%
57.81%
59.38%
60.94%
62.50%
64.06%
65.63%
67.19%
68.75%
70.31%
71.88%
73.44%
75.00%
REGISTER
1,1,0,0,0,0
1,1,0,0,0,1
1,1,0,0,1,0
1,1,0,0,1,1
1,1,0,1,0,0
1,1,0,1,0,1
1,1,0,1,1,0
1,1,0,1,1,1
1,1,1,0,0,0
1,1,1,0,0,1
1,1,1,0,1,0
1,1,1,0,1,1
1,1,1,1,0,0
1,1,1,1,0,1
1,1,1,1,1,0
1,1,1,1,1,1
DUTY
76.56%
78.13%
79.69%
81.25%
82.81%
84.38%
85.94%
87.50%
89.06%
90.63%
92.19%
93.75%
95.31%
96.88%
98.44%
100.00%
The relation between the PWM REGISTER and SENS voltage is reversed by the “REV” bit, as follows.
TABLE 2 REV vs. PWM REGISTER
REV
PWM REGISTER
PWM REGISTER0
PWM REGISTER1
0
PWM REGISTER2
PWM REGISTER3
PWM REGISTER4
PWM REGISTER5
PWM REGISTER6
PWM REGISTER7
PWM REGISTER7
PWM REGISTER6
1
PWM REGISTER5
PWM REGISTER4
PWM REGISTER3
PWM REGISTER2
PWM REGISTER1
PWM REGISTER0
Note 1) For the information on the relation between PWM duty and LED current (ILED), refer to “(9-1) PWM DUTY and LED
CURRENT“.
Note 2) For the information on the relation between SENS voltage and PWM REGISTER, refer to “DC ELECTRICAL
CHARACTERISTICS”.
-6-
Ver.2003-10-23
NJU6051
(5) SERIAL INTERFACE
(5-1) SERIAL DATA WRITE
The serial data is latched into the shift register on the rising edge of the serial clock (SCK), and determined
on the rising edge of the data request (REQ). The serial data format should be the MSB first.
For COMMAND data transmission, the command data 1 (CMD1) and the command data 2 (CMD2) should
be continuous. The CMD1 is first, then the CMD2. If only 1-byte data is transferred, this data is recognized as the
CMD1. Do not transmit 3 bytes or more, because 3rd data is used only for maker test and the 4th and later are
ignored. If it's absolute necessary to send the 3 bytes or more in the user's application, the only data
(0,0,0,0,0,0,0,0) as the 3rd data can be accepted.
For DUTY data transmission, 8 bytes for PWM REGISTER 0-7 should be continuous. The order is : PWM
REGISTER 0, 1, 2, 3, 4, 5, 6 and 7. If 7bytes or less are transferred, all bytes are accepted. And if 9 bytes or more,
the 9th and later are ignored.
Note that the data should be in 8*n bits (n=integer number), otherwise it may cause malfunctions. And the
SCK should be “0” when the REQ is changed.
SERIAL DATA FORMAT
TABLE 3-1 Command Data 1
B7
B6
B5
B4
0
SOFF
BRIGHT
TABLE 3-2 Command Data 2
B7
B6
B5
B4
0
0
0
0
TABLE 3-3 Duty Data
B7
B6
B5
1
*
FIGURE 1
B4
B3
B2
STBY
B3
0
B2
0
B1
HOLD
B0
REV
B1
B0
DIVIDE
B3
B2
PWM REGISTER
B1
B0
COMMAND DATA TRANSMISSION
REQ
SCK
DATA
B7
6
5
4
3
2
1
0
B7
6
5
4
CMD1
FIGURE 2
3
2
1
0
0
B7
6
CMD2
DUTY DATA TRANSMISSION
REQ
SCK
DATA
B7
PWM REGISTER
Ver.2003-10-23
6
5
4
3
0
2
1
0
B7
6
1
0
B7
6
6
7
-7-
NJU6051
(5-2) SENSOR DATA READ
The DATA terminal becomes output state by setting the REQ terminal to “1” after the command data
transmission. And the sensor data is read out, synchronizing with the SCK. The bit number corresponding to a
selected register is “1” and the others are “0”, as shown below.
FIGURE 3
SENSOR DATA READ (REV=0, PWM REGISTER4 selected)
REQ
SCK
DATA
B7
0
Command Data (Input)
1
2
3
4
5
6
7
Sensor Data (Output)
(5-3) SOFF and BRIGHT
By setting “1” at the SOFF bit, the luminance sensor control is disabled and the PWM duty is controlled by the
BRIGHT bits, as shown below.
TABLE 4 SOFF and BRIGHT
SOFF
BRIGHT
REV
0
-
0
1
000
001
010
011
100
101
110
111
-
PWM REGISTER
PWM REGISTER0
PWM REGISTER1
PWM REGISTER2
PWM REGISTER3
PWM REGISTER4
PWM REGISTER5
PWM REGISTER6
PWM REGISTER7
PWM REGISTER0
PWM REGISTER1
PWM REGISTER2
PWM REGISTER3
PWM REGISTER4
PWM REGISTER5
PWM REGISTER6
PWM REGISTER7
Note 1) When SOFF=”0”, luminance sensor control is enabled and PWM REGISTER is selected according to SENS voltage.
Note 2) For the information on the relation between SENS voltage and PWM REGISTER, refer to “DC ELECTRICAL
CHARACTERISTICS”.
(5-4) STBY
By setting “1” at the STBY bit, the NJU6051 goes into the standby mode, as follows.
- DC/DC converter, oscillator, reference voltage generator, and power supply for sensor are halted.
- The contents of PWM REGISTER are maintained.
- Luminance sensor control circuit is initialized.
-8-
Ver.2003-10-23
NJU6051
(5-5) HOLD
By setting “1” at the HOLD bit, the selected PWM REGISTER is held and the luminance sensor control
cannot be used. In other words, this setting works so that the luminance of the LEDs doesn’t change even if the
SENS voltage changes. The selection is initialized to the PWM REGISTER 0 by the reset. And when the standby is
released, the selection is initialized to the PWM REGISTER 0 at REV=“0” or the PWM REGISTER 7 at
REV=“1”.
(5-6) REV
By setting “1” at the REV bit, the correspondence between the PWM REGISTER and SENS voltage is
reversed.
TABLE 5 REV
REV
0
1
PWM REGISTER
PWM REGISTER0
PWM REGISTER1
PWM REGISTER2
PWM REGISTER3
PWM REGISTER4
PWM REGISTER5
PWM REGISTER6
PWM REGISTER7
PWM REGISTER7
PWM REGISTER6
PWM REGISTER5
PWM REGISTER4
PWM REGISTER3
PWM REGISTER2
PWM REGISTER1
PWM REGISTER0
(5-7) DIVIDE
By setting the DIVIDE bits, the sensor-sampling-time (tSENS) and PWM frequency (fPWM) are changed. Note
that these parameters are varied depending on the oscillation frequency (FOSC). The formula (2) gives the
sensor-sampling-time.
t sens =
TABLE 6
2 (17 + N )
f OSC
(sec)
--- Formula (2)
SENSOR SAMPLING TIME
DIVIDE
N
00
01
10
11
0
1
2
3
FOSC
100kHz
1.311
2.621
5.243
10.486
200kHz
0.655
1.311
2.621
5.243
400kHz
0.328
0.655
1.311
800kHz
0.164
0.328
0.655
2.621
1.311
UNIT : sec
Ver.2003-10-23
-9-
NJU6051
And, the formula (3) gives the PWM frequency.
f pwm =
TABLE 7
f
1
⋅ ( 3osc
64 2 + N )
( Hz )
--- Formula (3)
PWM FREQUENCY
DIVIDE
N
00
01
10
11
0
1
2
3
FOSC
100kHz
195.3
97.7
48.8
24.4
200kHz
390.6
400kHz
781.3
390.6
195.3
97.7
48.8
195.3
800kHz
1562.5
781.3
390.6
97.7
195.3
UNIT : Hz
NOTE) PWM frequencies written in bold or neighbors are recommended, otherwise it might cause LED flickering.
(6) LEVEL SHIFTER
The level shifter allows the communication with the MPU working at the power supply voltage lower than the
VDD. Apply the MPU power-supply-voltage on the VDDL terminal. The voltage range is: 1.8V<VDDL<3.6V .
(7) RESET
By setting the RSTB pin to “L”, the NJU6051 is initialized into the following default status.
TABLE 8 RESET
REGISTER
REV
HOLD
STBY
BRIGHT
SOFF
DIVIDE
PWM REGISTER1-7
DATA
0
0
0
000
0
00
000000
Default status
Refer to Table 5
Sensor sampling is enabled
Standby Off
Luminance sensor control is enabled
PWM duty 0% (LED off)
(8) TEMPERATURE COMPENSATION
The reference voltage (VREF) generator has temperature compensation, which suppresses the characteristic
degradation of LEDs at high temperatures. Refer to “ILED vs. Temperature” shown in the “DC Electrical
Characteristics”.
- 10 -
Ver.2003-10-23
NJU6051
(9) APPLICATIONS INFORMATION
(9-1) PWM DUTY and LED CURRENT
The average LED current is programmed with the single resistor RLED and the PWM duty, as shown in
Formula (4).
I LED(avg) = I LED(max) ⋅
I LED(max) =
DUTY
100
--- Formula (4)
VREF
RLED
(9-2) INDUCTOR SELECTION
Formula (5) is used to choose an optimum inductor, as shown below:
V

2 OUT − VIN  ⋅ I LED
η

L=  2
I LIMIT ⋅ f OSC
η
--- Formula (5)
: Power conversion efficiency (= 0.7 to 0.8)
The power supply voltage VIN may fluctuate in battery-powered applications. For this reason, the minimum
voltage should be applied to the VIN in Formula (5).
The NJU6051 has about 200ns of delay time (TDELAY), which is defined as the period from the reach of the
current limit 470mA to the MOS-switch-off. The TDELAY may cause an overshoot-inductor-current, which is called
the peak current IL,PEAK, and calculated by Formula (6). Therefore, it is recommended that an inductor with a
rating twice of the IL,PEAK and a low DCR (DC resistance) be used for high efficiency.
 VIN (max) − VDS 
 ⋅ TDELAY
I L,PEAK = I LIMIT + 
L


--- Formula (6)
VDS
: Drain-Source voltage of the MOS switch (=ILIMIT*RON)
VIN(MAX)
: Maximum of VIN Voltage
(9-3) DIODE SELECTION
A Schottky diode with a low forward-voltage-drop and a fast switching-speed is ideal. And the diode must
have a rating greater than the output voltage and the output current in the system.
(9-4) CAPACITOR SELECTION
A low ESR (Equivalent Series Resistance) capacitor should be used at the output to minimize output ripples. A
multi-layer ceramic capacitor is the best selection for the NJU6051 application because of not only the low ESR
but its small package. A ceramic capacitor as the input decoupling-capacitor is also recommended and should be
placed as close to the NJU6051 as possible.
Ver.2003-10-23
- 11 -
NJU6051
! ABSOLUTE MAXIMUM RATINGS
PARAMETERS
VDD Power Supply
VDDL Power Supply
SYMBOL
VDD
VDDL
Input Voltage
VIN1
Input Voltage
VIN2
Switch Voltage
VSW
Power Dissipation
PD
Operating Temperature
Storage Temperature
Topr
Tstg
NOTE1)
NOTE2)
NOTE3)
CONDITIONS
CX/TCLK, REF,
FB, SENS terminals
REQ, DATA, SCK, RSTb
Terminals
SW terminal
RATINGS
-0.3 to +6
-0.3 to VDD
UNIT
V
V
-0.3 to VDD+0.3
V
-0.3 to VDDL+0.3
V
+18.0
640 (QFN20)
540 (SSOP20)
-40 to +85
-55 to +125
V
Ta=25°C
NOTE
3
4
5
mW
°C
°C
All voltages are relative to VSS = 0V reference.
Do not exceed the absolute maximum ratings, otherwise the stress may cause a permanent damage to the IC. It is
also recommended that the IC be used in the range specified in the DC electrical characteristics, or the electrical
stress may cause mulfunctions and affect the reliability.
The switch voltage VSW is the highest voltage in the system. This voltage must not exceed the absolute maximum
rating.
VSW =VF(LED) x N(LED) +VF(D1) +VREF
VF(LED)
N(LED)
VF(D1)
:Forward Voltage of LED
:The Number of LEDs
:Forward Voltage of Diode D1
For instance,
when VF(LED) = 3.6V, N(LED)=4pcs, VF(D1)=0.3V, VREF=0.6V(TYP), VSW = 3.6V x 4 + 0.3V + 0.6V = 15.3V.
NOTE4)
NOTE5)
- 12 -
Mounted on the glass epoxy board (50mm x 50mm x 1.6mm)
Mounted on the board specified by EIA/JEDEC (2-layer FR-4, 76.2mm x 114.3mm x 1.6mm)
Ver.2003-10-23
NJU6051
! DC ELECTRICAL CHARACTERISTICS
VDD=3.0 to 5.5V, Ta=-40 to 85°C
PARAMETERS
VDD Power Supply
VDDL Power Supply
Output Current
SYMBOL
VDD
VDDL
IOUT
Reference Voltage
VREF
Operating Current
Standby Current
VSO Power Supply
PWM REGISTER0
Selected Voltage
PWM REGISTER1
Selected Voltage
PWM REGISTER2
Selected Voltage
PWM REGISTER3
Selected Voltage
PWM REGISTER4
Selected Voltage
PWM REGISTER5
Selected Voltage
PWM REGISTER6
Selected Voltage
PWM REGISTER7
Selected Voltage
IOPR
ISTBY
VSO
3.0
1.8
MAX.
5.5
3.6
30
Ta=25°C
DC/DC Converter OFF
fosc=500kHz
0.558
2.23
Unit
Note
V
V
mA
1
0.60
0.642
V
2
0.8
1.2
1
2.57
mA
uA
V
3
4
5
2.40
0
0.007VSO
V
VD1
SENS terminal, REV=0
0.015VSO
0.020VSO
V
VD2
SENS terminal, REV=0
0.030VSO
0.040VSO
V
VD3
SENS terminal, REV=0
0.060VSO
0.090VSO
V
VD4
SENS terminal, REV=0
0.110VSO
0.180VSO
V
VD5
SENS terminal, REV=0
0.220VSO
0.360VSO
V
VD6
SENS terminal, REV=0
0.440VSO
0.720VSO
V
VD7
SENS terminal, REV=0
0.880VSO
VSO
V
0
0.2VDDL
V
0.8VDDL
VDDL
V
0.2VDDL
V
Input “H” Level
VIH
Output “L” Level
VOL
Output “H” Level
VOH
Oscillation Frequency
Oscillation Duty
fOSC
DOSC
Switch Current Limit
ILIMIT
Ver.2003-10-23
RATINGS
TYP.
SENS terminal, REV=0
VIL
Over Voltage Protection
MIN.
VD0
Input “L” Level
Switch On Voltage
CONDITIONS
VDS(on)
VOVP
SCK, DATA, REQ, RSTB
terminals
SCK, DATA, REQ, RSTB
terminals
DATA terminals
VDDL=1.8V, IOL=0.4Ma
DATA terminals
VDDL=1.8V, IOH= - 0.04mA
VDD=3V, CX=47pF
VDD=3V, CX=47pF
SW terminal, VDD=4.2V
VFB>VREF/2, Ta=25°C
SW terminal, VDD=4.2V
ISW=470mA, Ta=25°C
VOUT terminal
0.8VDDL
V
350
70
500
75
650
80
kHz
%
400
470
580
mA
1
1.4
V
17.5
6
V
- 13 -
NJU6051
NOTE1) Output Voltage Test Conditions
! TEST Command
B7
0
0
! TEST Circuit
LED
VDD :5V
D1
L1
C1
C2
R1
RLED
fOSC
B6
1
1
B5
1
0
B4
1
0
B3
1
0
B1
0
0
B0
0
0
:VF=3.6V, ILED=20mA
:Schottky diode
:6.8uH
:4.7uF
:1uF
:100kΩ
:40Ω
:500kHz / Duty 75%
L1
VDD
B2
0
0
D1
C1
A
VDD
R1
SW
VOUT
VDDL
C2
CPU
DATA
REQ
SCK
FB
RSTb
RLED
SENS
CX/TCLK
- 14 -
VSS
Ver.2003-10-23
NJU6051
NOTE2) TEMPERATURE COMPENSATION
The reference voltage (VREF) generator has temperature compensation, which suppresses the characteristic-degradation of
LEDs at high temperatures. The VREF is regulated to 0.6V typical in the temperature range up to 45°C, and gradually decreases
as the ambient temperature rises in the range higher than 45°C.
VREF[V]
1.0
0.5
0.0
-50
-25
0
25
50
TEMPERATURE[℃]
75
100
VREF VS TEMPERATURE
FIGURE 4
VREF vs. TEMPERATURE
ILED[mA]
30
RLED=30Ω
RLED=40Ω
20
10
0
-50
-25
0
25
50
TEMPERATURE[℃]
75
100
ILED VSTEMPERATURE
FIGURE 5
Ver.2003-10-23
ILED vs. TEMPERATURE
- 15 -
NJU6051
NOTE3) Operating Current Test Conditions
! TEST Command
B7
0
0
B6
1
1
B5
1
0
B4
1
0
B3
1
0
B2
0
0
B1
0
0
B6
*
1
B5
*
0
B4
*
0
B3
*
0
B2
B1
1
*
0
0
*: ”Don’t care”
B0
0
0
NOTE4) Standby Current
! TEST Command
B7
0
0
B0
*
0
! TEST Circuit (Operating Current, Standby Ciurrent)
:VF=3.6V, ILED=20mA
:Schottky diode
:6.8uH
:4.7uF
:1uF
:100KΩ
:40Ω
:500kHz / Duty 75%
LED
D1
L1
C1
C2
R1
RLED
fOSC
VDD
C1
A
R1
VDD
SW
VOUT
VDDL
C2
CPU
DATA
REQ
SCK
FB
RSTb
RLED
SENS
CX/TCLK
- 16 -
VSS
Ver.2003-10-23
NJU6051
NOTE5) VSO Power Supply Test Condition
! TEST Command
B7
0
0
! TEST Circuit
LED
D1
L1
C1
C2
R1
R2
RLED
fOSC
B6
1
1
B5
1
0
B4
1
0
B3
1
1
B1
0
0
B0
0
0
:VF=3.6V, ILED=20mA
:Schottky diode
:6.8uH
:4.7uF
:1uF
:100KΩ
:1KΩ
:40Ω
: 500kHz / Duty 75%
L1
VDD
B2
0
0
D1
C1
VDD
R1
SW
VOUT
VDDL
C2
CPU
DATA
REQ
SCK
FB
RSTb
SENS
VSO
V
Ver.2003-10-23
RLED
CX/TCLK
VSS
R2
- 17 -
NJU6051
NOTE6) OSCILLATOR
The built-in oscillator incorporates a reference power supply, so its frequency is independent from the VDD. The frequency
is varied by the external capacitor CX, as shown below.
fOSC(kHz)
fOSC vs CX
1000
900
800
700
600
500
400
300
200
100
0
0
100
200
300
400
500
CX(pF)
Figure 7
fOSC vs. CX
(Reference but not guaranteed)
- 18 -
Ver.2003-10-23
NJU6051
! AC ELECTRICAL CHARACTERISTICS
VDD=3.0 to 5.5V, Ta=-40 to 85°C
PARAMETERS
SYMBOL
SCK Clock Cycle
SCK Clock Width
tCCY
tWSCH
tWSCL
tREH
tDAS
tDAH
tD0
tRES
tWREH
tr
tf
tRSL
“H” Level
“L” Level
REQ Hold Time
Data Set-Up Time
Data Hold Time
Output Data Delay Time CL=20pF
REQ Set-Up Time
REQ High Level Width
REQ,SCK,DATA Rising Time
REQ,SCK,DATA Falling Time
RSTB Pulse Width
MIN.
RATINGS
TYP.
MAX.
1.0
400
400
800
400
400
400
800
1.0
-
200
100
100
-
UNIT
us
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
us
Serial Input Timing
REQ
tREH
tWSCL tWSCH
tWREH
tRES
SCK
tDAS
tSCCY
B7
DATA
B6
tDAH
B5
Bn
B0
Serial Output Timing
REQ
tREH
tWSCL tWSCH
tRES
SCK
tDO
tSCCY
DATA
B7
B6
B5
Bn
B0
Reset Input Timing
tRSL
RSTb
0.3VDD
Ver.2003-10-23
0.3VDD
- 19 -
NJU6051
! TYPICAL APPLICATION CIRCUIT
L1
D1
VDD
C1
VDD
SW
VOUT
VSO
C2
SENS
R1
VDDL
FB
DATA
CPU
REF
REQ
RLED
SCK
RSTb
CX/TCLK
VSS
TEST
[CAUTION]
The specifications on this databook are only
given for information , without any guarantee
as regards either mistakes or omissions. The
application circuits in this databook are
described only to show representative usages
of the product and not intended for the
guarantee or permission of any right including
the industrial rights.
- 20 -
Ver.2003-10-23