1
LT3505EDD
DESCRIPTION
Demonstration Circuit 1395A is a
1.2A, Step-Down
Switching Regulator in a 3mm × 3mm DFN
. The
LT3505EDD is available in an 8-pin (3mm × 3mm)
DFN surface mount package.
L
, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered
trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy
Drive, FilterCAD, Hot Swap, LinearView, μModule, Micropower SwitcherCAD, Multimode
Dimming, No Latency
ΔΣ
, No Latency Delta-Sigma, No R
SENSE
, Operational Filter, PanelProtect,
PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT,
UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names
may be trademarks of the companies that manufacture the products.
PERFORMANCE SUMMARY
Specifications are at T
A
= 25°C
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX UNITS
HVIN
High Voltage Input Voltage Range
Input disabled from 36-40V
8
40
V
5V ADAPTOR
5V Adaptor Input Voltage Range
4.5 5.5
V
HVBUCK
Output Voltage Range
Range is mode and load dependant
3.5 5.5
V
I
HVBUCK
Output Current
2
A
QUICK START PROCEDURE
Using short twisted pair leads for any power con-
nections, with all loads and power supplies off, refer
to Figures 1 & 2 for the proper measurement and
equipment setup.
A companion PMIC demo board is required for this
check out procedure. The DC1303A
(LTC4098EPDC) board is recommended, and will be
used for the following procedure. Please refer to
the DC1303A Quick Start Guide for further informa-
tion.
Follow the procedure below:
1.
Set PS1 to 8V, PS2 to 0V, and PS3 to 3.6V. Set
Load1 to 0A. Ensure that jumpers are config-
ured as per Figure 1, except the “D2” jumper
(JP3) on the DC1303A should be set to “1”.
2.
Observe that 4.50V < VOUT (VM3) < 4.70V. The
LT3480 HV Buck regulator is running with its
control loop closed locally. The nominal
HVBUCK voltage is 4.75V, and the
LTC4098EPDC on the DC1303A board has con-
nected HVBUCK to VOUT.
3.
Set Load1 to 1A. Observe that 4.35V < VOUT
(VM3) 4.55V. Set Load1 to 0A. The 1A load on
VOUT loads HVBUCK, so the LT3505EDD is
supplying 1A.
4.
Set PS1 to 36V. Observe that 4.50V < VOUT
(VM3) < 4.70V. The LT3505 is designed to op-
erate from HVIN = 8V to 36V.
5.
Set Load1 to 1A. Observe that 4.20V < VOUT
(VM3) < 4.55V. Set Load1 to 0A. The LT3505
is now supplying 1A, while operating from 38V.
6.
Set “COMP” jumper (JP2) to “REMOTE”. Ob-
serve that 3.80V < VOUT (VM3) < 4.10V. The
LTC4098EPDC is now controlling the LT3505
output voltage to approximately V(BAT) + 0.3V.
7.
Set Load1 to 1A. Observe that 3.70V < VOUT
(VM3) < 3.90V. Set Load1 to 0A. LT3505 is
supplying 1A, while under LTC4098 control.
8.
Set PS1 to 8V. Observe that 3.80V < VOUT
(VM3) < 4.10V.
QUICK START GUIDE FOR
DC1395A
LT3505EDD:
PMIC High Voltage
Adaptor Board with 5 Volt Adaptor Inputs