LT3745 Просмотр технического описания (PDF) - Linear Technology
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LT3745 Datasheet PDF : 28 Pages
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LT3745
Timing Characteristics The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VIN = 12V, VCC = 3V to 5.5V, VEN/UVLO = 1.5V, VFB = 1.5V,
VISP = VISN = 5V, VLEDxx = 1V, RT = 105k, RISET = 60.4k, CCAP = 0.47µF to VIN, CSCKO = CSDO = CLDO = 15pF to GND, unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
fSCKI
fPWMCK
tWH-CKI
tWL-CKI
tWH-PWM
tWL-PWM
tWH-LDI
tSU-SDI
tHD-SDI
Data Shift Clock Frequency
PWMCK Clock Frequency
SCKI Pulse Duration
PWMCK Pulse Duration
LDI Pulse Duration
SDI-SCKI Setup Time
SCKI-SDI Hold Time
SCKI = H (Figure 3)
SCKI = L (Figure 3)
PWMCK = H (Figure 4)
PWMCK = L (Figure 4)
LDI = H (Figure 3)
SDI – SCKI ↑ (Figure 3)
SCKI ↑ – SDI (Figure 3)
l
l
l 16
l 16
l 20
l 20
l 20
l
2
l
2
30
MHz
25
MHz
ns
ns
ns
ns
ns
ns
ns
tSU-LDI
SCKI-LDI Setup Time
SCKI ↓ – LDI ↑ (Figure 3)
l
5
ns
tHD-LDI
tPD-SCK↑
tPD-SCK↓
∆tPD-SCK
LDI-SCKI Hold Time
SCKI-SCKO Propagation Delay (Rising)
SCKI-SCKO Propagation Delay (Falling)
SCK Duty Cycle Change
LDI ↓ – SCKI ↑ (Figure 3)
SCKI ↑ – SCKO ↑ (Figure 3)
SCKI ↓ – SCKO ↓ (Figure 3)
∆tPD-SCK = tPD-SCK↑ – tPD-SCK↓
l 15
ns
l
17
35
ns
l
20
40
ns
–3
ns
tPD-SD
SCKO-SDO Propagation Delay
SCKO ↑ – SDO (Figure 3)
l 2.2
4.5
7
ns
tPD-LD↑
tPD-LD↓
∆tPD-LD
tPD-PWM
tR-SO
tF-SO
LDI-LDO Propagation Delay (Rising)
LDI-LDO Propagation Delay (Falling)
LD Duty Cycle Change
PWMCK-LED Propagation Delay
SCKO/SDO/LDO Rise Time
SCKO/SDO/LDO Fall Time
LDI ↑ – LDO ↑ (Figure 3)
LDI ↓ – LDO ↓ (Figure 3)
∆tPD-LD = tPD-LD↑ – tPD-LD↓
PWMCK ↑ – ILED (Figure 4)
CLOAD = 15pF, 10% to 90%
CLOAD = 15pF, 90% to 10%
l
17
35
ns
l
20
40
ns
–3
ns
80
ns
4
ns
4
ns
Table 1. Test Parameter Equations
∆ILEDC(%)
=
IOUTn – IOUTavg(0−15)
IOUTavg( 0 − 15)
•
100
(1)
∆I LEDD(%) =
IOUTavg(0−15) – IOUTcal
I OUTcal
•
100
(2)
IOUTcal
=
2500
•
1.205V
RISET
(3)
∆ILINE (% / V) =
IOUTn
VCC = 5.5V – IOUTn VCC = 3V
IOUTn VCC = 3V
•
100
2.5V
(4)
∆ILOAD (% / V) =
IOUTn
VOUTn = 3V – IOUTn VOUTn = 1V
IOUTn VOUTn = 1V
•
100
2V
(5)
3745f
5
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